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Old 07-24-2008, 07:57 PM   #526
rayclark
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My build is coming along very nicely. Since you have stated that the dimensions are not all the critical I decided to make all panels the nice even number 6 inches.

Question on the rudder though...have you found it to make any difference as to the size of the rudder part that moves. Looking at the pictures posted thruout this thread I am seeing different sizes of the rudder past the hinge line so I am assuming that it doesn't make to much difference. Correct me if I'm wrong.

Seems like the hardest part of building this plane is having to wait for the glue to dry.

As soon as I finish building I will get some pics posted.

RC
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Old 07-24-2008, 09:22 PM   #527
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Larry,

Yes my hinges are as you say, criss-crossed, I will make a drawing and add it to this post. BUT - THE HINGES FOR THE CAP are just strips of Monocote 2.5" x 1" hot glued in place, no ironing at all.
I came up with a neat way to apply them, take a plastic ruler, 1" wide, wrap the end with masking tape, inside out (!!!) and it becomes a grabber to hold the hinge. Slap a hinge against it, add glue to the hinge, and press it in place, hold until cold and peel off the homemade grabber tool.
**** EDIT y09m10d14 I have been using RTV hinges lately, takes a day to cure, but work well-see later posts ****

I will post my accumulated notes, all copies of what you have said, so it should sound familiar. I added some notes, and edited things, but it is true plagarism at it's finest. As Sir Francis Bacon said "plagarism is the most sincere form of appreciation" (NOT AN EXACT QUOTE...) Here are your notes:

1.WATERPROOFING, 2.MOTOR, 3.CG, 4.CONTROLS, 5.PAINT,
6.THRUST LINE, 7.GLUE, 8.BUILD STEPS, 9.TRIMMING
================================
1. WATERPROOFING

If you plan to fly off water - get some CorrosionX water proofing stuff. They have it at the Ace hardware/lumber yard next door to the hobby shop. It can be found in most Ace hardware stores and many Marine supply stores.
Get the standard (NOT the heavy duty) Marine or Aviation CorrosionX. I prefer the pump spray bottle and not the aerosol spray can, but either will work. The pump spray is a lot easier and neater because you can take the lid off to poor it into a jar for use. The aerosol can is a lot of trouble to get some into a jar for dunking. You will waist a lot.
This stuff is like medium weight oil - about 20-30 weight or so.

Pour some into a large mouth glass jar or small deep bowl. Make it enough to completely cover the parts. Dunk the rx, speed control and motor into the jar and swish it around so that the stuff penetrates all the nooks and crannies. Take the rx case off, if you can, so the gunk can get to the electronics easily. It needs to contact and coat the electronic circuit boards.
Make sure it gets inside the heat shrink on the speed controller too. Get all the air bubbles out. Also be sure all the connectors get a dose.
Once the part is all coated remove it from the oil - I use long nose pliers - and let most of the stuff drip back into the jar. I then put the parts onto several layers of paper towels and let them drain over night. Turn the stuff a couple of times to try to get as much of the oil to drain out as possible. Wipe the outsides of everything off as best you can with more paper towels. Then wipe it again - then wipe it again - then wipe it again and again etc.

Be warned - this stuff stinks some (my wife hates it) and if you get any onto something else you will never get glue or tape or paint to stick to that place again. Its a good idea to wash your hands very very well after using it and before touching anything else. Its persistent stuff!
You may think you have drained the part very very well and then lay it down on your wife's pretty new kitchen table - your doomed because another drop will decide to drain out just then
If you want to use sticky back Velcro on the rx or speed controller, you will need to wipe the outside of the case or shrink tubing down with alcohol to get it as clean as possible or the sticky will never stick. Don't get the alcohol on the electronics as that will remove the waterproofing. It also may kill the circuit.
Sounds like a lot of trouble but it will save you blowing up a speed controller or rx if (when) it gets dunked under water. Believe me - if you fly off water it will end up upside down at some point!

I have deliberately run treated motors and controllers and rx's while they were completely under water. Amazing stuff. The TV commercial shows them treating a TV set then tossing it into a swimming pool and watching TV under water.
I put a lid on the used CorrosionX left in the jar and keep using it till its gone. Keep a lid on it as it stinks and may evaporate over time. If you can get the bottle instead of the can you can poor it back in.
I re-treat my stuff once a year and it is doing great. The only things that it didn't work well on were servos. 1 out of 3 or 4 went bad when treated.

On my Capricorn, itís not unusual for the plane to get blown over upside down in the water. (itís the wind - not dumb thumbs.) More often than not, that same wind will catch it and blow it right side up again. So far, I have been able to wait a few moments and fly off the water again as if nothing had happened. I have had the plane upside down for as long as 15-20 minutes with the receiver, controller and motor completely submerged the entire time. When it flips back upright again - off I go with no issues. I have found that sometimes it doesn't work. If water is touching the pins on the receiver crystal it will de-tune the receiver and it wonít work until the water drains off the crystal. If that happens, just remove the crystal and blow on the socket and you good to go again.

I do NOT treat servos as mentioned above. Too many of them die on me. I also do NOT treat my batteries. There is tape covering the electrical contacts on most all battery packs. The CorrosionX causes the tape to stop sticking and uncovers the contacts. Not a good thing.
After a dunking I do NOT use that battery pack again that day. I take it home and put the battery in front of a fan to dry it out as best I can. I leave it there for at least a day before re-charging. So far, after many many dunkings, I have had no battery problems.

Do NOT fly off salt water. It will kill the battery packs in just a few minutes and I don't know how well the CorrosionX would work on protecting the esc's and RX's in salt conditions. They use it for Marine electronics, but they don't normally expect a complete dunking in salt water.
CorrosionX is truly amazing stuff.

P.S. Do NOT be tempted to run your motor while its under water with a prop attached to try to 'motor boat' back to shore. The water has soooo much extra resistance compared to air that the motor will draw huge currents and over load. You will probably kill the controller or battery if you try it.
As always with electrics - the FIRST thing to do if you crash - on water or land - is kill the throttle.
2. MOTOR

Any small brushless will work fine if it can put out 100 watts or more peak and you could probably fly "sport" with as little as 60 watts.
The wing loading of a typical shock flyer is about 4.5 ounces per sq foot. A Tensor 4D is down to about 3.5 oz/ft. The Capricorn is about 2.5 oz/ft at the lightest.
My latest version weighs around 16-18 ounces all up and I like flying it on a Mikrodan 2505 motor with a 3S TP 1320 pack. It draws about 9 amps for around 100 watts peak with a GWS 9x5 prop. Itís more than light enough to fly in the smallest spaces or indoors yet still has plenty of power for wild maneuvers and water or wet grass takeoffs and is a hoot to fly outdoors in the wind.
The vast majority of each flight is spent well under 1/2 throttle.




3. CG

I like flying with my CG about 9-10 inches back from the leading edge. I have flown it as far as 15" back but thatís a bit much.
Jed and most other folks prefer being about 7-8 inches back - right at the rear of the sponsons. Itís a lot more stable and tracks better with it at that point.
However, if you want to do those super tight loops you need it back about 9".

When your flying off water and the model gets wet, the CG moves back a good bit. Again because most of the surface area is behind the CG anything added to the entire surface moves the CG rearward.
Itís more noticeable the further back your CG us to start with. If you have your cg around 7" back it wont be a problem, but be prepared for a more sensitive elevator response.
4. CONTROLS

Specific Control Hardware

1. AXI 2212/26 motor (towerhobbies.com) or a torque t22/930 from (extremeflightrc.com)
2. APC 11x4.7 prop--towerhobbies
3. Berg 4 receiver----towerhobbies
4. Thunderbird 36 speed control---towerhobbies
5. 1800-2600 3 cell lipo battery---cheapbatterypacks.com
6. Velcro to stick everything together
7. Blenderm tape for hinges.. top and bottom----medical store or on line
8. HS 55 servos or HS 65 servo---towerhobbies
9. Krylon H2O paint...It must be H2O or it will eat the foam----Walmart
10. Dubro 930 horns---towerhobbies
11. Durbro easy connecter---towerhobbies
Controls - General

HS55's servos seem to have plenty of power. I have stripped out several of them after crashes though. I like the '55's because they are cheap and have enough power, but also because if you bump a surface while loading etc it will NOT automatically strip the gears like some of the small servos do.

Original has enough ground clearance for a 16" prop so on my next one I will mount the motor down lower - even with the top of the main wing. That will reduce the need for so much UP thrust .

HEAT SHRINK - I haven't had any fail in flight, but I have had a couple tear after hard crashes that also stripped out the servo gears.
Some heat shrink seems to be better than others though. I had some that was kind of stiff before shrinking. Felt more like drinking straw plastic rather than the usual rubbery stretchy kind. That stuff didn't work at all. It tended to break after just a couple of bends once it cooled.
Just remember to sand the ends of the carbon rods smooth so they are not sharp and have no rough edges. Also bend the joint 90 degrees as you shrink it - in the direction its going to be working once its installed - and let it cool in that position.

The elevon push rods were made from 1/8" carbon tube split down the middle. The last inch or so is not split and has an outer sleeve to stop the split at that point. The back of the push rods have 1" bits of threaded rod lashed and glued in place. The clevises go on the threaded rod and allow individual adjustment of each elevon.

Pull-pull could be tried as per design on ďPull-pull.dwgĒ

I decided to do all the hinges and servo work before putting the W into the wing; much easier to work with everything flat. The wing panels are joined with tape at this time to allow them to hinge and form the W easily.
Added water rudder area is glued on bottom of fin for better water steering.

The only other change I make in the tx is to run a lot of expo. I generally use around 60%-70% expo on elevator and aileron. Zero on rudder. I dont use dual rates - Im maxed out all the time.

However, thats because of the way I like to fly.

How you set up the controlls as far as throws, expo, dual rates, etc depends mostly on how you like to fly.

I like to fly on the ragged edge with this thing - very tail heavy and as much throw as physically possible. The rudder goes about 60 degrees either way and the elevons go around 50 degrees up/down on mine.

Thats what you need if your going to do wild manovers one second then slow to a crawl the next and cruise 1 inch off the water or drag one sponson around the circle. Thats also why I fly with 60%-70% expo so I can keep it stable and smooth at slow speeds and still do wild stuff without having to flip a switch.

Most people have a hard time with that, but its what Im used to.

I would recommend you start off with a mild set-up to get started unless you are a wild 3D junkie who like to do low inverted spins and tumbles at hi speed.

I would set things up with about 45 degrees of throw on hi rates and mabey 15-20 degrees on low rates and set the CG at around 7 inches from the pointed nose to start.

Fly it and see how you like it. Adjust the throws and cg to taste as you get used to it.

This thing flys a bit differently than most any other plane out there and it takes a bit of adjusting.

The best advice I can give you is:

1) dont fly at full throttle all the time. This thing will take off and cruise around nice and easy at very low throttle settings. Its a ***** cat at slow speeds. It can get a little psychotic at hi speeds and a rear CG

2) Use the left stick.

I do 90% of my turning with the rudder. When Iím low-n-slow I control altitude with throttle and use the elevator to set the angle of attack and steer with rudder.

I have use several different things for color. The sponsons are painted - mostly with Krylon H2O but Iíve used other latex paints as well. On the wing I am currently using some low temp covering material - I think its UltraCoat but canít remember for sure - the labels are long gone I have also done hand painted stripes with craft paint and a foam brush when I was in a hurry.

Regular Monocoat is not a good idea as the shrink temps are too hi and the foam will melt. Make sure what you use says 'low temp' somewhere on the label.

5. PAINT

Be careful with paint. If you paint the entire thing it adds a LOT of weight. Thatís a lot of area and it adds up. It also tends to make the model more tail heavy so keep that in mind too as most of the paint added will be behind the CG.
6. THRUST LINE

On thrust angles - how much up thrust you need varies depending on how hi the motor is mounted above the top V joint.
The taller the motor mount, the more up thrust you need.
On my small version, I was able to mount the motor very low - right on the V. That one didnít need any up thrust.
Lowering the motor height caused more of a change than I expected in the thrust line. I think Iím going to have to add some DOWN thrust.
I wonít make that decision until I get a chance to fly it outdoors and do some more trimming flights. I need to get the CG right before I mess with the thrust angle. I think the CG needs to go back more too, but I need some more room to test that properly. Our indoor space is just too small to allow for proper trimming. Youíre constantly turning to miss the walls!
Also got to do some trimming flights. I think the thrust line is fine. The CG just needed to go back a good ways. Iím almost perfect now.
Right thrust isnít critical. This isnít a pattern plane and I doubt you'd notice if it was set to zero. I wouldnít bother trying to cut the slots on an angle.
What I do is just glue the stick on slightly cocked to one side, then add a side brace in Depron. Sometimes I have done a brace on both sides when Iím running larger motors.
All of mine do have a small amount of right thrust. I donít measure it - its TLAR
7. GLUE

For glue on the main wing joints - Gorilla brand glue or any similar expanding Polyurethane type glue will work best by far. I like the Sumo brand because its white and looks the best. It has the worst bottles though. Very tough to squeeze. I have used CA and epoxy but they seem to be more brittle and the joints have broken easier.
I usually use foam safe CA on the motor mount and to glue in the rudder but the PU or epoxy will work as well.
My current favorite for the wing joints - by far - is the new Gorilla Fast Cure clear polyurethane glue that dries white. I also like the Sumo brand but the bottles are tough to squeeze. I use some foam safe CA here and there when Iím in a hurry.
I just found some new Gorilla glue.
It looks clear in the bottle and says "Quick Cure/Dries White".
I just tried some and it does dry faster and ends up white.
The bottle is much easier to work with than the Sumo glue too.
I like it a lot so far.



8. BUILD STEPS


I found out that the blue is Styrofoam and the pink is the cyanosomething?
That means that the blue would be relatively safe to cut with a hot wire, but the pink will put out very very nasty fumes.

1) After you cut the main wing parts out, bevel them for joints and for hinges. Since Blenderm tap slowly ďcreepsĒ, use modified Monocote hinges, requiring two V-shaped mating edges, ===><===.

2) Start with the 2 panels on one side and bevel then tape the outside of the joint while its laying flat.
3) Turn it over and add glue to the joint.
4) Weight the inside piece and prop up the outside tapered piece 4" to 5" off the table. That will give the proper angle. Brace it some way so it canít move while the glue cures. I use scraps of Depron and some pins.
5) As the polyurethane glue cures, it will expand up out of the joint. During the first 1/2 hour or so you can run a Popsicle stick over the joint and scrape off the excess as it comes out. You will end up with a nice joint if you stay after it from the beginning. Wait too long and you'll have to sand it or try to cut it off. Mix the glue with water first to speed it up.

Once the outer panels are done, you can do the center joint the same way. Pre-cut the slots for rudder then put glue in the joint then flip it right side up and put braces at each end then let the glue cure. I donít bother scraping out the excess as it foams up because it will not show and its impossible to get to using this method anyway

A note on the angle of the outer panels - it doesnít matter
I just checked and I have 3 different bend angles on various versions. Prop up the outer panels anywhere from 4" to 5". They all fly fine ")

The sponsons are made from 2" thick pink building insulation board. I get mine from Home Depot in 2' wide x 8' long sheets for about $20 or so
I have also used pool toy "Noodle board" foam for the sponsons. It has the advantage of being similar to EPP foam in that it bends and springs back after a crash. The down side is that is a pain to work with as far as getting glues to stick and it only comes in ugly colors.

Try painting or low temp iron-on covering to waterproof the foam, if it absorbs water (Blue, Pink, Expanded bead, Styrofoam all absorb water.) This is still an unconquered problem. May try Depron in an inverted ďTĒ or a channel with an open back for drainage.

Larry covers the bottoms of his sponsons with plastic cut from large jugs of cat litter. Glued on with 3M 77 spray adhesive. It lasts forever and is very slick. Works better on grass and snow than duct tape, though Duct tape will work and is cheep and easy. It wears out fast on pavement but is easy to replace.
Others have had good luck with the thin baking sheets from Target. They are Teflon or something similar. Very slick and tough but pricey.

Put the electrical components in the space between the deck and the under brace - you will have to make the brace width to fit. Lay this out first and cut the fin slot before final assembly
Seal up the front unless you suspect overheating is a problem.
In the winter it would probably help keep the packs warmer so you would actually get better performance on very cold days.
Be sure to leave the back end open so any water that does get inside can drain out.

To mount the sponsons cut a 'v' shaped notch in the top and then glue them to the outer joints of the 'w'. The angles donít have to be perfect - the Gorilla glue will expand to fill in any gaps.

Servos - wrap with masking tape glue them down, on top of the wing.
Donít cut a hole in the deck for servos; mine have been filing up with water since I did that.

Wing strength, two choices:
1. Double up the layers in the front, for strength. It also makes the plane stiffer so it rolls better. It keeps the main wing from breaking at the join line where the under brace glues to the wing deck.
On hard landings the sponsons tend to spread outward. That puts a bending moment on the center wing panels and it tends to break along the line where the brace is glued on.
2. A dowel running between the sponsons works well. It can get caught on tall weeds It is a lot stronger though.

My doubled-up section holds up fairly well but it still can break along that joint on a rough landing. Last time I broke it I glassed the joints about 4" back with .5 oz glass and water based varathane.
Keep in mind I tend to be rough on mine. I like to fly close to the ground/water and many of my low loops tend to bottom out an inch or so below ground level. The "spring action" of this design allows it to flex and come back - but only so far
This thing is long and flexible as far as twisting. When you give it a roll command the fuse has a tendency to twist in the opposite direction which tends to counter act your roll command. The bottom brace was originally added to fight that, then made larger.
When I added the top front layers that really helped a lot. I suspect a wider bottom brace would have the same effect.

I donít like using hollow LE mounted tubes in this situation. The structure needs to be able to flex or it wonít last long. On the 6MM version I think 2.5mm or 3MM rod would be fine.
I still prefer the doubled front edge because it serves a dual purpose - it reduces the wing twist and helps roll rate at the same time.
If you do use carbon - remember I donít have any really good reason NOT to - it needs to be at the front as I mentioned before. Thatís where most of the weight is going to be carried.


9. TRIMMING

By the way - here is how I test for correct thrust angles.
First you must get the CG set correctly. If itís too far forward or too far back, the up thrust cant be set as well.
Again, this isnít a pattern plane so itís not all that critical.
Get the CG where you want it, the closer to ďneutralĒ the better (but twitchier) it will be.
Neutral CG requires no trimming for level flight between inverted and upright.

Next, trim the model so it flies straight and level at full throttle. Then abruptly cut the throttle.
If the model climbs when you chop the throttle, then you have too much down thrust.
If the model abruptly dives, then you have too much UP thrust.
Ideally, the model should start a slow decent with no abrupt up or down pitches when the throttle is cut.
You can also check by starting at low speeds and abruptly go to full power. If the model climbs radically = too much UP thrust.
If it dives = too much down thrust.
Be aware that climbing/diving with throttle changes can also be caused by nose/tail heavy condition so thatís why you set the CG first.

To check right thrust, first go high then point the model at you and dive at about a 45 degree angle - power off.
Trim the rudder for a straight 45 degree glide with no side to side turning. By the way - this is also another way to check for issues - the glide should be dead flat on the 45 with no climb or diving away from the 45 degree line.
Once the rudder trim is set, then do the same thing but do it climbing away going UP on a 45 with power on. Does the model pull to either side? Adjust side thrust as needed.
You can also check by climbing straight up and see which way it pulls, but the 45 degree climb is going to be closer to your normal flying speed, so I like it better.

I also copied your drawing, converted it to inches, and lowered the motor, I will get that added to this post too. Please note that I revised it, use the newer one.

I wil add newer versions as I redraw this, check for newest date "yXXmXXdXX" is year-month-day


Attached Files
File Type: pdf Capricorn y08m07d24.pdf (19.8 KB, 1877 views)
File Type: pdf Monocote Hinges.pdf (14.0 KB, 1091 views)
File Type: pdf Capricorn y08m07d27.pdf (21.7 KB, 1480 views)
File Type: pdf capricorn y09m09d02d.pdf (68.9 KB, 1275 views)
File Type: pdf capricorn y09m10d12a.pdf (72.6 KB, 1967 views)
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Old 07-25-2008, 01:52 AM   #528
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Originally Posted by rayclark View Post
My build is coming along very nicely. Since you have stated that the dimensions are not all the critical I decided to make all panels the nice even number 6 inches.

Question on the rudder though...have you found it to make any difference as to the size of the rudder part that moves. Looking at the pictures posted thruout this thread I am seeing different sizes of the rudder past the hinge line so I am assuming that it doesn't make to much difference. Correct me if I'm wrong.

Seems like the hardest part of building this plane is having to wait for the glue to dry.

As soon as I finish building I will get some pics posted.

RC
Yeah - all the controll surfaces can be sized to taste - BUT - I like them BIG!
I especially like big rudders and I extra especially like big rudders on this particular model.

However - that depends on how you like to fly. If you dont use much rudder, then dont worry too much about it.

I have to tell you though - bigger is better on the rudder on this thing

I think I need a signature.
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Old 07-25-2008, 01:53 AM   #529
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DBacon - thats quite a colection! I havent had time to read it all, but thanks!

I think I need a signature.
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Old 07-25-2008, 02:33 AM   #530
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Larry,

Maybe it will answer the main questions, and I should edit it as per your direction, or add new things as they become discovered.
There are places where I changed your words to match what I wanted to do when I build it. I hope I don't confuse people with this.

Tomorrow I will make my sponsons. I will try expanded bead covered in iron-on mylar, because that stuff sucks water like a sponge. If that doesn't work out, I may try just "skis" of depron to see if it floats high enough. My measured weight of everything except sponsons is only 16 oz. so I may get away with that.

If that fails then it gets pink foam, painted to stop it from absorbing water.

I have tried expanded bead styro, regular styro, pink foam, and blue foam, and found them all to absorb water. Very frustrating, but Depron seems OK. These are listed in order of weight.

Also tomorrow I will test my pull-pull linkage. I think it won't gather weeds, as I fly off water exclusively. For people who fly from grass, the point you made about the lower horn gathering things is one to watch out for.
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Old 07-25-2008, 04:00 AM   #531
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Larry,

Sorry about asking so many questions. I thought from your explanation that the mini capricorn flew different than the big one so I assumed that the data on the big one did not apply. At least now anyone that reads pages 16-21 will be able to successfully build the mini without difficulty.

I guess the orthodontist in me had to have all the facts before starting the project.

I hope to build mine this weekend.

Rick
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Old 07-25-2008, 07:29 PM   #532
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Sorry guys - Ive been swamped and will answer later.....

I think I need a signature.
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Old 07-25-2008, 11:13 PM   #533
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Larry,

You don't need to give me any answers, on the contrary, I was trying to free you up by summarizing things on the Capricorn. I was doing that for myself anyway. Being an engineer, I must get everything all well understood before I start, sounds like an Orthodontist, but I can't spell that...

I finished my sponsons, they are 6mm Depron boxed in and sealed with hot glue. Last time I made them that way was for my MHO, but I was disappointed because of all the leaks. I was surprised to find that GG leaks, quite a lot! So the hot glue will not, but I sure get tangled up in all those spider webbie things from all the frantic glueing...

My total weight is 20 oz (hot glue is heavy) but not bad for such a big plane. My home-made motor only has 16 oz thrust, but it should be OK, I am not a good enough pilot to "hot dog" around anyway...

Pictures soon will include my pull-pull system which is working pretty good so far...
0445 Front shows rudder servo with pull-pull cables. Nosepiece under
motor is removable.
0446 Top shows two black tubes for balance checking one at 7", one at 9".
servos as far fwd as practical in attempt to balance it.
0447 Bottom shows both 2mm CF tubes, pull-pull wires, rudder is lower
than original plans for water steering, sponsons are hollow, made of 6mm
Depron sheet.
0448 Under elevators shows pull-pull "horns" made of 6mm Depron
triangles. Monocote strips hot glued for hinges are a little ugly.
0449 Under wing LE shows bottom of servo arms with two pull-pull wires
attached.
0450 Top of wing LE shows servo and arm, two wires attached. Magnets
that hold nose piece can be seen near the servo wire.
0451 Nose piece off, shows all components as far forward as practical.
There is a bulkhead inside to keep components forward. "Components" are
Battery, Radio, Elevon mixer, & ESC.
0453 Clearance for CF tubes not too bad, but weeds still could hit
pull-pull linkage.
0454 back of plane, rudder is full left, wide bottom plate did wonders to
make the plane rigid and resist twisting.

EDIT July 27:
WELL I HAD TO CHANGE THINGS....
1. The rear CF rod had to go, it was dragging sideways through the water, like a sea anchor, so it's gone.
2. The deep V sponsons were wrong, shouldn't have deviated from Larry's plans, they got replaced with flat bottom ones, and they extend back 1/2" behing the CG now too.
Now it zips along fine, and lifts off the water so smoothly...


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Old 07-26-2008, 09:31 PM   #534
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I got my son, the RC pilot, coming over tomorrow, but I thought I would put it on the lake to see it scoot around. It would hardly move, like it was glued down!
I tooled around and around until the battery was just about flat, it would not lift off at all, just no speed.

The motor has 16 OZ of thrust, and was a screamer in my MHO. The Cap weighs in at only 20 OZ, so I thought it would do OK. I have a hotter motor on order, so I will switch to that if nothing else works. It will have 34 OZ of thrust, but requires a bigger battery too...

I put it on the grass, and it immediately got up to speed and lifted off, but I set it right back down, don't want to explain to my son that I crashed it.

So my question to anybody - Do you think my sponson design is causing a lot of drag? They are not made like Larry's plans, I made them out of 6mm Depron with a hollow center, to save weight, and avoid water absorption. That worked well, but it just couldn't get up on plane.

Do you think the V-shaped bottom is doing this, and that I should have a flat bottom, like Larry's plans?

It also sits level in the water, and maybe it should point a little skyward. I also have zero up and right thrust.
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Old 07-26-2008, 11:27 PM   #535
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Sorry, Im still rushed, but here are some quick observations.

1)The deep V hull shape is designed to cut through the water rather than cruise on top of it. Water creates huge huge huge amounts of drag so you need to be out of it as much as possible. Im afraid you need to switch to a more flat bottom design. Dont forget to keep the edges sharp - dont be tempted to round them off so they look good. Round edges at the water line create more drag.

1A)I think the V hull is also not holding the nose up hi enough out of the water so you can get a positive angle of attack on the wing. You need that to take off.

2) It looks like the lower horns on your pull/pull will be dragging in the water. Thats going to also create more drag. Im also thinking that carbon tube you have at the rear is dragging in the water. Thats going to create even more drag.

You dont need the carbon tube at the rear. Ive never broken one there in all my crashes or hard landings.

If you look at the drawings and pics you can see that Ive let the rudder/fin hang down below the bottom brace so it comes close to, but not quite on, the ground when its sitting flat.

Thats for two reasons. It helps with water steering at slow speeds if the rudder is in the water AND it keeps the center section from spreading when it hits the ground. That keeps the stress off that rear joint.

You would not believe how much drag water causes. Its actually harder/takes more power to take off on water or to cruise thru water than it is on the ground or even grass.

For starters Id get rid of the carbon tube at the rear. Its possible that may be eoungh to let it take off.

Next step would be to redo the sponsons. Thats a shame because they sure do look pretty!

I think I need a signature.
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Old 07-26-2008, 11:37 PM   #536
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The rear of mine.

Notice how the rudder hangs down - almost but not quite - to the ground when its sitting level.

No extra reinforcement needed.

As it gets going up to speed on the water, the rudder is raised up OUT of the water so there is no extra drag. Thats why it doesnt hang down all the way.

The sponsons also need to be tall enough so that the entire rear of the plane is completely up out of the water when your cruising on step. If not - it will be very hard to get to take off speed.

Remember that the rear of the plane has to be able to move DOWN so that the front can have some positive angle of attack and get wind under the wing. If not it wont lift off.


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I think I need a signature.
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Old 07-26-2008, 11:59 PM   #537
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Thanks Larry, everything you said is happening, deep V drag, CF tube drag, horns drag, angle of attack is zero, I guess it all adds up! I will fix 1, 2 and 4, hope to live with 3.
Round tubing through air is bad, I imagine through water is 10x as bad, I will get rid of it. Actually the 7" wide lower brace gave it such rigidity, I don't need anything else. It is that wide to allow stuffing all the gear inside.
Gotta go get it ready for the test pilot...

Thanks again.
Then new sponsons are already drawn up, so I am ready to build! Thanks for the nice words on the existing ones, you wouldn't believe how I got the pattern for the curve, I used a tapered fishing pole, tied it back with a wire to put an elliptical bow in it, and traced it out, sweet.

The back CF tube is clearly in the water, and the front is low.


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Old 07-27-2008, 06:02 AM   #538
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From those pics it looks like the pull/pull horns may be ok once your at speed.

Actually, those sponsons might even be ok if the drag from the tube is gone. You might be able to get enough speed to get them up on top of water. It will probably take more spees than with flat bottoms but they mey be ok.

You might consider removing the tube before modifying the sponsons and give it a try.

If you can get it up 'on step' with the tail end completely out of the water, Id bet it will take off.

Remember - you need to let it get all the way on step before you give it UP elevator. If the tail ends drags in the water (from too much UP too soon) it will slow it down a LOT.

I think I need a signature.
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Old 07-27-2008, 08:03 AM   #539
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Larry,

When I took the picture of the back and saw that tube in the water, I once again said "Thank you Larry". You imagined that long before the picture even showed it.

I absolutely agree with your advice, remove the tube first and try it.

It will be easy to make new sponsons if I need to, as I have learned how to deal with this hot glue pretty well. I have a Monocote "trim iron" that works like a hot knife, and opens glued joints right up.

I am really liking the hot glue, I just wish that it held up better in a closed up car. My Son's Mig that I made with hot glue sat in the closed van for a few hours and the nylon elevator horns fell off. My inside thermometer usually indicates 110 degrees under these conditions. I am using "Dual Temp" glue, but my research on glue sites shows the glue maintains strength to 190 degrees (???)
Maybe the nylon doesn't work well with it...
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Old 07-27-2008, 10:43 AM   #540
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DBacon and Larry. Post 527 is a good summary of this thread. I am busily engaged in making a step by step Capricorn variation thread with tons of pictures and some new ideas on RCG. I'm doing it there rather than here because it is an easier format to explain the photos. May I please have permission to quote post 527 there if I give you credit and post a link to this thread?

I have only worked in larger heavier scale but here are some things I have learned.

I have built many a larger seaplane and learned that the pontoons work better if they are square and ugly (at least where they contact the water). The instant a plane starts to move forward the plane should be pushed up and out of the water by the pontoon. The plane needs to be able to rotate on step to about 1" per 12" length to be able to take off easily at low speed. If you get your step too far back the plane won't rotate. If the step is too far forward and it will bounce on a faster landing. The step should be about 1/2 inch behind the CG for optimal performance. The step helps the plane tear loose from the water. When the pontoon is tapered or rounded it creates drag. The rounded pontoon also throws more spray that tries to find it's way to your radio and into your prop.

Dropping a small rudder in the water helps especially in the wind. I used to attach a small piece of aluminum or tin to my rudder to drag in the water.
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Old 07-27-2008, 01:55 PM   #541
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RC'ers are a great bunch, it is guys like Lee that proves this, thank you for your respect of my note-taking, I certainly approve, but please remember Larry is the one who originated all this, I just "cut-and-Pasted" it into a compilation, it is HIS work!.

As far as my plane, I am about to remove the underwater drag chute (the crosswise CF brace) and test it. If it is OK I will leave the deep V sponsons, because they give great directional stability, but I am ready to make them flat, both you and Larry make a lot of sense.

I am not having trouble with the splashing, but I was impressed by the amount of water that climbs up each side of the sponsons. When I get a little more speed it will probably be a problem as you explained. But I am ready with the hot glue gun (low temp) and can make changes very quickly...

As far as CG and Step, the Step is 7" back, and the CG was supposed to be 7" back, but I was not able to achieve this, it is 9" back from the wing LE. So I need to make the sponsons go back 2 1/2" further when I rebuild them, again, no problem to do. If the sponsons were flat-bottomed now, I bet I could just extend the bottom back with a piece like a boat's trim plate to achieve the point to rotate about.
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Old 07-27-2008, 03:54 PM   #542
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Don't worry...I haven't forgotten Larry. I appreciate all he has done and his patience with this thread. He and I have been in contact.

It is hard to be a thread leader and stay with it so it will stay alive. Larry has done a great job.

I design and cut EPP wing cores and planes for our club. I get asked the same questions over and over again as new people start to build. I learned a good building instructions with photos are the next best thing to having someone build it for you. When I get my photos finished and posted I will definitely link you all to it.
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Old 07-27-2008, 04:33 PM   #543
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Took the Cap up last night. Was very successful...no tree landings. Cap flew differently than I am use to, but it flys nice. Goning to try and get some flight time into today and work with the CG a little. Seems to be close, but not perfect yet. Also going to experiment with some different prop sizes. I am using a FC-28-22. Does anyone have a recommended prop for this motor. They claim a 10" on the HC specs, but I think that is a little much. It pulls about 15 amps with a 1060 gws prop.

Here are a couple of pics.

RC


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Old 07-27-2008, 04:35 PM   #544
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Lee,

Now you will have two threads to keep up on. I could put your link in my summary, might keep things compact for the readers.

I changed the floats, the new ones are 2 1/2" longer to get the step 1/2" behind my 9" CG. The before and after look the same from the side but the new ones are flat bottom, 2" wide, all the way to the tip.

I had to come back and edit this, thanks Larry, thanks Lee, it zips along great. And on that tiny little motor. It lifted off and I had controlled flight for about 50 feet, but I set it down because my Son is coming soon, and I want him to test it first, he is much better than I am, I am just the pit crew...


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Old 07-27-2008, 07:29 PM   #545
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Lee,
I just checked out your site, man you put some work into that. I will respect your wish to not post things there yet, I hope everybody honors that wish too, so you can get it finished. Actually there isn't any more needed to build these from your plans. Be sure to tell me when I can reveal your link, I am sure everybody will want to participate.
You show special tools, mass production, plans all organized to fit on one sheet, you have really thought this one out.
When your club launches all of these, there will be headlines in Utah about a mass UFO invasion!
Egad, you have an arsenal of specialized irons!
Is this a rerun of "Attack of the clones"?
I saw a stack of 40 rudders!
And all those references to hardware, great job.

I found all the foams I tried, including blue foam, absorb water. The only exception I found was Depron. The blue and pink foams can be painted to stop this but the really light ones, styrofoam and expanded bead styro can't be cured with paint, as they suck up too much!
Do you find FFF not to absorb water?
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Old 07-28-2008, 02:49 AM   #546
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Default Capricorn night flyer

This is a great design, Larry. Very nicely done and thanks so much for sharing it. After I heard about this plane from Lee, I had to build one for myself...and put lights on it. Here's a video from our night flying test last night. Winds were gusting from 5-7 mph but it handled quite well. Still a little wobble in the turns since my CG is a little bit aft.



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Old 07-28-2008, 05:42 PM   #547
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You guys have all been busy!

Im short of time at the moment so I'll get back to you all later.....

I have to say - great job so far Lee, congrats DBacon and I love the lights Darth!

I think I need a signature.
Larry
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Old 07-29-2008, 03:21 AM   #548
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Got some more flight time in today. With the motor I'm using a 9 x 3.8 prop seems to work pretty well.

Have a question though...Upright this thing flys great but doesn't fly worth a darn inverted. It keeps wanting to roll back over upright. I was wondering if maybe I got to much angle in the outer wing panels. Not sure if this would do that or not. Any suggestions?

Thanks

RC
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Old 07-29-2008, 04:00 AM   #549
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Originally Posted by rayclark View Post
Got some more flight time in today. With the motor I'm using a 9 x 3.8 prop seems to work pretty well.

Have a question though...Upright this thing flys great but doesn't fly worth a darn inverted. It keeps wanting to roll back over upright. I was wondering if maybe I got to much angle in the outer wing panels. Not sure if this would do that or not. Any suggestions?

Thanks

RC
Hi Ray,

Thats very odd. One of the most unusual and remarkable characteristics of this plan form is that it is extremely stable when inverted. All of mine are hands off when inverted in the roll axis. Its actually takes a bit of effort to get it to roll all the way at slow speeds.

Let me ask a few questions....

Is it doing this only at hi speeds or very slow speeds or both?

How much right thrust have you got built in?

Does it want to always roll out to level the same direction - IE right roll all the time or left roll all the time?

Is your rudder dead straight?

Its hard to tell, but it looks like your right sponson is slightly angled to the right side? It could just be the angle of the photo but - Check both to see if they are both lined up dead straight as far as left/right angles as well.

Looking at your pictures posted earlier, I think the wing panel angles are well within the range of the various ones Ive built so I doubt thats the issue.

Remember earlier on I said that I do most of my steering using the rudder?

Thats because the rudder is very effective on this model BUT it also has a strong secondary effect and thats in the roll department.

This model has huge roll coupling with the rudder. In essence, it has a large effective dihedral because of the outer wing panels being angled the way they are. This means that any rudder input that causes the plane to fly at an angle/yaw instead of flying straight forward, will also cause a strong rolling action at the same time.

Normally, with a plane that has dihedral, when its inverted the roll coupling is still there but its in the wrong direction AND you loose the stability that dihedral gives you.

The Capricorn on the other hand acts like it has dihedral in BOTH directions at the same time. Its normally extremely stable when upright OR inverted and the rudder still induces a strong roll - but its in the correct direction whether its upright OR inverted.

What Im suspecting on your model, is that something is causing yours to fly in a crabbing or side slipping manner. Something is inducing a yaw that is then causing a roll. It could be several things.

The most likely are the issues I asked about above - the rudder is out of alignment or it could be a sponson.

The sponsons have a large side area thats located forward of the CG. Its very important that they be straight on to the flight direction. The sponsons are for all practical purposes large rudders located in a bad spot - forward of the CG.

Thats one reason why this model does better with large rudder/fin areas. They need to offset the side area of the sponsons or the plane will fly like its tail heavy in the rudder/yaw direction - it will be unstable in yaw. That yaw instability translates into roll instability because any time this thing yaws it also rolls.

It could also be a thrust line issue - you may need more right thrust. You can check this if it does the roll out only when its under power and not when the power is off.

The other possibility is that it could be out of balance latteraly.

Check the side to side balance. If its off a good bit that means you will have some aileron trim dialed in to fly wings level when upright. However, that same trim correction thats perfect when its right side up, will cause the plane to roll out when its inverted. A warped wing section could cause the same thing.

Turn the planes tx and rx on and look at it from the rear (assuming its already trimmed for straight and level flight) and see if the elevons are close to the same up/down alignment on each side with the main wing. If one side is off a good bit you probably have a weight issue or a warp.

Lastly - it could easily be a combination of these things. A little of this and a little of that - if they are all going in the same direction - can add up to a bad habbit.

Check those things and let us know.

I think I need a signature.
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Old 07-29-2008, 11:13 AM   #550
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It does take some juice to fly the way it should. Mostly to just get off the ground. Does anyone use a 2s? Mine requires a 3s. I need to devise a better rudder linkage. Seems like everytime i touch down any harder than a feather, the control horn pops out. Whats the smallest Capricorn so far? Just catching up with an awesome thread.
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