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-   -   $75.00 Build Contest: Arado 555 (http://www.Wattflyer.com/forums/showthread.php?t=72824)

pmullen503 12-18-2013 03:56 PM

$75.00 Build Contest: Arado 555
 
3 Attachment(s)
Ok, so this is my entry for the $75 build contest: Gotha 244 from the late Jack Bale. I found the plans on Outerzone.co.uk (http://outerzone.co.uk/plan_details.asp?ID=4802). Unlike lot's of old plans I have, this one is very complete, so complete I contemplated just building it as is from balsa. But I've decided to do at least the nacelles from formed foam.

The Gotha may seem like an odd choice but it has a lot going for it. The twin boom will make it a pain to store and transport, but the twin boom and lack of retracts mean that the fuselage can be removed with only a single connection for ground steering. It also means that the fuselage can be replaced with one designed specifically for AP or FPV, which is something I wanted for some time. The projected weight should give "trainer-like" performance.

Specs:

WS 82"
Area 706 sq/in
Weight Goal 70 oz. (2 kg.)
Motors (2) 3536 1100 KV 9-10" prop
Battery 4000 to 5000 mAh 3s

xmech2k 12-18-2013 04:52 PM

Neat subject! This is turning into my favorite contest here, as I always love the rare planes.

Tsavah 12-18-2013 04:57 PM

$75 Build Contest - Gotha 224
 
Dang, that is a lot of model airplane for 3s! Want to see this one go for sure. The size is what I am the most interested in since I want to go bigger.

hayofstacks 12-18-2013 05:35 PM

x2.

id stick with the larger battery if it were me, and it balances okay.

I'm pulling 49 amps out of my plane, 55oz and a 4000mah battery and only getting about 20 minute flight times.

pmullen503 12-18-2013 08:35 PM

Quote:

Originally Posted by xmech2k (Post 934790)
Neat subject! This is turning into my favorite contest here, as I always love the rare planes.

The Gotha 244 is that.

Quote:

Originally Posted by Tsavah (Post 934792)
Dang, that is a lot of model airplane for 3s! Want to see this one go for sure. The size is what I am the most interested in since I want to go bigger.

The difference is two motors and only 9-10" prop disk. That and I have a a lot of 3s batteries. I should get a combined total of about 2 kg thrust which will be plenty for this type of plane.

pmullen503 12-18-2013 08:47 PM

Quote:

Originally Posted by hayofstacks (Post 934793)
x2.

id stick with the larger battery if it were me, and it balances okay.

I'm pulling 49 amps out of my plane, and a 4000mah battery and only getting about 20 minute flight times.

I'm only planning 8-10 minutes with (2) 2200 3s mAh batteries at about 1/2 throttle.

CHELLIE 12-18-2013 08:56 PM

Cool, Neet Build

pmullen503 02-10-2014 01:38 AM

I've decided to change the model I'm going to do for the contest. First, a computer crash meant I lost all my work on the original Jack Bale plan. No problem, I'll just get the plan enlarged and build from balsa. So I get a couple full size prints and start pricing balsa and plywood. I guess I've never actually done that for a model of this size :eek:! Ok, substitute foam for some of the balsa and I'm back within the $75 budget. Then my propane supplier tells me that because of the propane shortage in the Midwest he can't fill the tank for the shop; only residences.

Turns out I have a friend who wants to build an Arado 555 and needs some help; and his shop is in the basement of his house.......

pmullen503 02-10-2014 02:11 AM

2 Attachment(s)
So I've been working on this for a week or so and it struck me that this would be a great project for the $75 seldom built contest. I'll catch up the posts over the next few days.

Arado 555 "Amerika Bomber"

I've been looking for a good Luft '46 project for some time and came across Josef Poisinger's Arado 555. The thing that I noticed was the somewhat unique use of a "slipway" analogous to the lower building board in the "laser method" I like to use. The size was good and I happened to have been looking for a project for a 1700kV 3530 motor I had.

I've converted much of the construction from balsa to foam methods but otherwise the plane will use all of the original's dimensions and airfoil.

The original plans and articles can be seen here: http://members.chello.at/karla.poisinger/

Specs:

WS 47" (1200mm)
Area 690 sq in.
Weight goal <40 oz.
Motor Turnigy 3530 1700kV

pmullen503 02-10-2014 02:17 AM

3 Attachment(s)
The first step was to redraw the plans for foam construction. The center part of the wing is made using the "laser method". Root and tip templates were generated from the files included in the Posinger download and Profile.exe. All I did was to alter the skin thickness for the $tree foam skin and changed the foam block to 3" thick. The printouts were then glued to formica and cut out to make the hot wire templates.

The building boards are melamine faced particle board. This is a good material to use because it's flat, cheap, and easy to clean blobs of glue off to use again. The wing layout was drawn onto one building board. All the rib blanks are vertical so I'll use the same drawing for right and left wing halves - the board with the layout is on top for one wing half and on the bottom for the other.

I glued 3" tall rib blanks to the layout board with blobs of hot glue. leveling the tops of the blanks, the second building board was glued in place with blobs of white Gorilla Glue. Once the templates were added it was ready to cut.

pmullen503 02-10-2014 02:21 AM

5 Attachment(s)
The first hot wire cut was made. I now had the rib blanks glued to the board with the wing's top profile cut.

I glued the $Tree foam top skin to the ribs. I like to use white Gorilla Glue for this step. Not only does it foam up to fill any imperfections in the hot wire cut ribs, cured glue itself can be hot wired through if applied thinly.

pmullen503 02-10-2014 03:04 AM

4 Attachment(s)
Once the top skin is on, it's trimmed at the root and tip and the lower wing templates are added. The top cut off is replaced but this time small pieces of double sided tape are added to adhere the wing to the top cut off. The key advantage to the "laser method" is that the wing is held straight at all times by virtue of being attached to the flat building boards.

The bottom cut is made and any internal structure or wiring access holes are cut. In this case, I choose not to add a spar or any additional structure. I did use the hot wire to make servo wire holes in the ribs.

The $Tree lower skin is then glued on.

pmullen503 02-10-2014 03:08 AM

2 Attachment(s)
Once both skins are glued on, the cut can be made for the balsa LE. This is easy and accurately done while the wing is still stuck to the building board. The hot wire and some templates make quick work of it.

The TE can be also be cut with the hot wire but I used a straight edge and an exacto knife to cut it to size. The TE will also get wood reinforcement, either round bamboo or square stock. I'll wait until the tip sections are done to add the TEs to the wing. That way I can tweek the chord a bit to make the main wing match the tip sections. The extreme taper in the tip sections will make them a little tricky to hot wire cut.

gramps2161 02-10-2014 03:15 AM

That is a sharp looking wing I just watched one of the videos and does it fly nice. Subscribe to follow along on your unique wing build.

CHELLIE 02-10-2014 03:38 AM

Quote:

Originally Posted by pmullen503 (Post 939581)
I've decided to change the model I'm going to do for the contest. First, a computer crash meant I lost all my work on the original Jack Bale plan. No problem, I'll just get the plan enlarged and build from balsa. So I get a couple full size prints and start pricing balsa and plywood. I guess I've never actually done that for a model of this size :eek:! Ok, substitute foam for some of the balsa and I'm back within the $75 budget. Then my propane supplier tells me that because of the propane shortage in the Midwest he can't fill the tank for the shop; only residences.

Turns out I have a friend who wants to build an Arado 555 and needs some help; and his shop is in the basement of his house.......

Neet Project :) Also, You might want to look into making a Fuelless heater. Money back guarantee if it does not work :D I think it works like shorting a battery, I always wanted to make one to try it out.

AN AMAZING NEW WAY TO HEAT YOUR HOME, BASEMENT OR GARAGE!
Can also be used to heat hot water for your hot water heater!


http://www.fuellesspower.com/8_Heater2.htm

pmullen503 02-10-2014 02:39 PM

Quote:

Originally Posted by CHELLIE (Post 939593)
Neet Project :) Also, You might want to look into making a Fuelless heater. Money back guarantee if it does not work :D I think it works like shorting a battery, I always wanted to make one to try it out.

AN AMAZING NEW WAY TO HEAT YOUR HOME, BASEMENT OR GARAGE!
Can also be used to heat hot water for your hot water heater!


http://www.fuellesspower.com/8_Heater2.htm


Let me know if it works! (Low tonight is forecast at -15F.)

baz49exe 02-10-2014 03:15 PM

Great choice. It looks like a large BV P.215 and that is a great flying design so I can't wait to see the results!!:D

Barry

pmullen503 02-10-2014 06:31 PM

If you go to the link in post #9 you can see video of the original flying. It flies well, even takes off from the ground!

pmullen503 02-10-2014 10:53 PM

4 Attachment(s)
I got the second half of the center section done. The two combined are 114g.

I got to work on the wing tips. The tip sections go from 15" chord to just 2.9" in only 10". That extreme taper causes some problems when trying to cut with a hot wire. The wire is traveling almost 5 times faster at the root than at the tip. To keep both ends of the wire traveling at the right speed a single template and pivot point was used. The problem was that because the slower traveling wire would leave a larger kerf at the tip, the tip chord would be smaller and thinner than it should be. The solution is to move the pivot point out (to make the tip chord larger) and back (because the effect is most pronounced at the TE) to keep the correct sweep and tip chord. I could say I expertly calculated the exact spot, but really I just guessed and moved the pivot point 2" farther out and 1" back from the theoretical pivot point.

The hot wire bow is held against the pivot point (bolt with nuts that form a slot wide enough for the wire and 1" above the board) and the other end follows the template.

I made a test cut on a 1lb/cu ft EPS and the core came out close enough to the correct size on the first try. Sticking down a fresh EPS blank, I made the top cut. I glued on a $Tree foam skin using the foam cut off and weights to clamp it. When that was cured I did the same for the bottom cut. The cut was made for the balsa LE.

It may seem odd to cover a solid expanded core with extruded foam skins but here is my reasoning: The $Tree foam leaves a nice smooth surface. The volume of the wing tip is pretty small. The weight saving would likewise be small if I had done the tips like the wing. I plan to cut out the elevons and face then with balsa for the hinges and a solid core gives me more to glue to.

The fall back position would have been to make them balsa sheeted, built up structures as in Poisinger's original plans.

Once covered with Kraft paper and WBPU the wing should come in under 350g; well within the budget.

pmullen503 02-10-2014 11:02 PM

5 Attachment(s)
I finished trimming the wing panels to size and gluing and shaping the LE and TE. The weight, ready to cover, is 190 g. I think I'll make balsa elevons. The foam TE of the tips are really flexible and will probably warp when covered with paper.

I thought I would show how I shape a balsa LE on a foam wing. The most important step is to protect the foam with a layer of packing tape before you start. That allows you to plane and sand the balsa down to the foam without damaging it.

I glued on the balsa with carpenters glue, not Gorilla Glue! You don't want any glue on the upper and lower surfaces of the foam; just where the balsa is glued on. Next, I laid pieces of packing tape on the top and bottom making sure they were stuck down flat.

After rough carving the shape with a knife, I used a block plane to refine the shape. The plane leaves nice straight line lines, unlike sandpaper. Even on a sanding block, the softer areas of the wood will sand more than the harder areas. The plane slides on the tape surface protecting the foam. Once you get to within a few thousandths of an inch, the tape will start to be cut by the plane. At that point I switch to sandpaper on a sanding block. 180 grit will quickly remove the planing marks. I sand the foam-balsa edge until the tape shows a uniform scratch pattern. Remove the tape and sand the entire wing with 240 or 320 grit and cover with paper and WBPU.

The last photo shows the rudders. Another interesting feature of Poisinger's 555 is that washout is achieved by mounting the tips at -3.5 degrees to the main panels. No washout is built into the panels themselves. The different panel angles are somewhat disguised by the way the panels mount to the rudder.

pmullen503 02-12-2014 01:11 PM

1 Attachment(s)
Here's the center section of the wing covered in Kraft paper and WBPU. Normally I'd wrap the paper around the LE and over lap at the TE but the paper isn't wide enough to cover the wing in one piece (root chord over 19" ). So here I overlapped the paper at both the LE and TE about an inch.

Work on a surgically clean surface. I start by cutting a piece of 30 lb. Kraft paper about 2" larger all around. Then I wet it with water from a mister. The goal is to dampen the paper so it will relax but not soak it. If needed I'll blot wet spots with a towel. Then I brush on a coat of WBPU with a foam brush; not dripping by saturated. I'll give the surface of the wing (sanded to 320 grit) a coat of WBPU too, again not dripping but thoroughly wet.

I pick up the wet paper (you can see why wet strength is important) and lay it on the wing. I smooth out wrinkles and bubbles and make sure the paper is in contact with the foam. In this case, I wrapped the LE and TE and marked where I wanted to trim the paper. Then I unwrapped the ends and cut it off the excess with a new exacto blade and yard stick.

I repeat the process on the other side. For the ends, I fold and roll the excess and secure it with binder clips.

I give the whole thing a final coat of WBPU. Then I hang it vertically in still air and let it dry slowly. The paper shrinks tight as it dries and adheres to the foam.

The weight of the two sect(450 sq in) was 120g. and the weight after trimming off the excess paper was 180 g. The wing is now very stiff and the paper gives good dent resistance. After the halves are joined I'll give it a quick sanding and one more coat of poly. That will be a good enough base for flat paint.

pmullen503 02-12-2014 01:15 PM

5 Attachment(s)
Here's a few photos of the tip sections.

I decided to make the elevons from sheet balsa so I cut those off and added 1/8" balsa faces to the cut edges and tips. When the glued on faces were dry and sanded I covered the wing tips with kraft paper.

The tips were small enough to cover both sides with a single piece of paper with the ends hidden in the hinge gap. The grain of the paper (the direction it tears straight) is parallel to the LE.

After trimming the weight is 76g. Total weight for the wing is around 250g.

pmullen503 02-12-2014 11:13 PM

3 Attachment(s)
Continuing to work on the wing tips. I built new elevons from sheet balsa. The new elevons are now very rigid.

I glued the rudders to the tip sections. The tips are mounted with 3.5 degrees negative incidence relative to the center sections. I drilled holes through the balsa rudder while they were stuck together for cutting so they would match each other. I connected the holes with lines and used nails to get the chord lines aligned at the right angle. Then I traced the airfoil onto the rudders. Now I can just glue the wing tips onto the center section using the traced airfoil outlines to get the proper angles.

pmullen503 02-13-2014 04:41 PM

5 Attachment(s)
Getting ready to join the parts. Before I can glue the wing sections together I have to get the motor pylon built and figure out where all the wiring will go. Since this plane really doesn't have much in the way of a fuselage, everything has to be stuffed inside the wing.

First I made the motor pylon out of balsa and plywood. 1/8" balsa sides enclose a wiring chase. Poisinger's original put the ESC in the motor nacelle but the fit is a little tight and the battery leads are longer than I'd like. I may put my ESC inside the wing near the battery but that will depend on how much heat the system puts out.

Either way I have to mount the pylon and there not much wing there so I made the pylon extend through the wing into what will be a 1/2"-3/4" tall skid that runs nose to tail. That should be solid enough.

I also wanted the option of using a 3 axis gyro. That works best when mounted at the CG so I created what will be a flat shelf when the wing halves are joined. The CG is just ahead of the motor pylon. I'll have to cut an access hatch later.

pmullen503 02-14-2014 02:38 AM

4 Attachment(s)
More progress. I added the servo wiring and elevon servos. Below is a shot of how they are mounted. The 3.5 degree "Schränkungssprung" provides just enough clearance for the control horn. Once the servos and wiring were in place the main panels could be glued to the end panels.

The two panels could finally be joined. At this point the wing, weighs 317g.

A quick check of the CG showed that the battery will be back into wing. Still have to mount the pylon, skid and make the fuselage.


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