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Hi-Performance and Sailplanes RC hotliners, electric pylon racers, F5B, F5D, sailplanes and gliders

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Old 03-27-2012, 01:59 AM   #1
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Default A "Screamin Demon" build electric from the ground up

I thought there may be some interest in this build on Watt flyer...
While this may not be a hotlinner, our your typical sailplane or pylon craft it is intended to be a "hi performance" airframe.
Never one to rush into things, I have finally started to build a kit I got back in August 2007,when this plane was first designed and produced. Originally I had thought of powering it with either a OS .40 FSR (still in the box) but in the long run I decided to go with the future and decided to go electric with it instead. At first I had hoped to power it with a large out runner like an Axi 4120 and fly it using a larger diameter high pitch prop. Due to current budget constraints (none) have made necessary to go a different route and use what I have on hand which is an Ammo 28-56-3200Kv motor similar to the HET 2W23 I used in my PQ stingray (which I have yet to get back into the air with what I hope is a better prop for it). This Ammo motor is rated for around 700 watts continuous and 1.5 kilowatt burst which gives it a current range of 45to 75 amps, with the cooling system and a heat sink added to the motor I may be able to get a bit better performance out of it but it is what I have to use so that's what the plane is going to be powered with.
With that in mind construction then started with building the motor mount and cooling duct, as they are needed in the preliminary stages of the airframe construction. I made up the cooling tube using the old plank method for construction with a plumbing piece as a mold that just happened to be the exact size to fit the motor with the additional heat sink into.
Then I made up some blanks for the cooling inlet/motor mount and cowl. With the blanks for the cooling tube and mount made up they had carbon fiber veil applied to reinforce them before they were turned then assembled into the complete assembly which makes up the motor mount and nose of the airplane. These blanks were then turned forming the inlet/mount and cowling shapes so they could be mounted onto the aft portion of the cooling duct which has it supports fastened to the sides so it fits into the bay between the ribs were to original plywood mount for a glow engine would normally go. The leading edge of the wing also attach to the motor mount, I am hoping this will really tie everything together and make a very rigid and stiff airframe time will tell but it seems to be the way to go with it. As I have very limited power it is important to keep the weight of this airframe as low as possible to make up for the lack of power, so every thing is being looked at in the build process with an eye to minimizing weight. The ribs had lighting holes cut into them to reduce a lot of weight, where this is plane is going to be powered with an electric motor I don't need the mass to counter the vibration of the engine and it can be a lot lighter construction then it normally would be with an a IC engine.
I made supports to hold the carbon fiber spars in place, these were then fastened in place over the plans and the ribs and motor mount then fitted onto the spars and fastened into place. Then I progressed to shaping the leading edges and wingtips and added them to the airframe the added the leading edge sheathing to tie everything together. Once they had dried I then applied the sheathing to the trailing edge at this point the weight was around 7 ounces so I hope that my target of a 2 lb all up weight can be achieved. I then added a shear web around all of the sheathing on the leading and trailing edge. The nice thing about the shear webs is that you can remove any sags or bows in the leading edge sheathing so it is straight and true with the wing, boy did this stiffen up the airframe!

I will post part two of this build shortly.


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That wasn't a crash, it was just a "hard landing".
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Old 03-27-2012, 04:41 PM   #2
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I made the center section as tight as I could because it is to be blended into the wing as much as possible. At this point the center section is still a work in process, one thing that is going to happen is that all of the control linkages will be contained within it, including the control horns to the torque rods for the elevons. It's going to get interesting designing and building that, the center section is going to be 2 1/4 inches high at it highest point so all I have to blend into the wing is the 1/2 inch difference on the sides. Part of the two center ribs you see will be removed to allow for space in body these were left intact until the dheathing was applied to the wings to maintain alignment of the parts. It was easier to locate them using the carbon fiber spars with the plan then to carve them out after most of the frame is completed to keep the shape true. This should keep the amount of frontal area to a minimum on this plane...
After installing the shear web around the inside perimeter of the sheathing I started to sheath the wing. Normally I do this in one large piece and call it done, but because of the modifications I am making for this electric SD at this point I decided to install more spars and shear web to make up for the fact that the forward carbon fiber spar will have the center removed. One of the reasons I decided to do this is that the 1/32 balsa I used for the shear webs added little weight the weight of the glue is probably more than the materials used. there are a few photos to show how this progressed. It was a tedious process of adding the shear webbing and doing the sheathing but I finally got it done! At this point it became clear that all of the work seemed to be worth it, the wing has become very rigid, it doesn't twist much which was a concern for me where I am going to be using the winglets and having swept the wingtips as well. This aspect of it was the primary reason for the added shear webs. Another reason for adding the shear webs is I am worried about the sheathing ballooning and distorting with the large bay area and thin sheathing. Well I can say that's it appears that the weight isn't to big of a problem at this point and the weight wasn't too bad at just over 10 oz.
At this point I am still trying to figure out how to exactly do the torque rods and mounting for them. One thing that became apparent at this point was with the center section I am going to have to shorten up the elevon span a bit. Somehow I have to compensate for shorting up the elevon span so I am planning to give the root of the elevon's a bit more cord, at least that way I maintain the same volume of control surface area even with the reduced span.
After getting the sheathing finished on the wings it was time to move on to the center section or the fuselage if you will. The firs thing was to add the supports for the belly pan. These were added to stiffen the sides of the center section and the sheathing on the belly pan (no landing gear on this one). After sheathing the belly here was the fist look at inside the "fuselage", lot of room in here compared to most hotliners or other "speed planes".
After getting the hatch ends frames and sheathed it was time to cut out the front spar's center section. (I sure hope the provisions I made for this is adequate!) After cutting out the spar I added the side supports for the hatch. Then I framed up the hatch in place for this application the hatch as to not only be airtight but a perfect fit as I want it to be able to carry the compressive force on the top of the wing that the front spar would normally carry. With this one battery size isn't going to be much of an issue the compartment size is roughly 10.5 inches long, 2.5 inches wide and 1 5/8 inches deep. Even adding the ESC and two servos there ought to be lots of room, and with a 10 X 2.5 hatch access to the internals it ought to be pretty easy to set up.
While I have really compromised the ability for this plane to tolerate negative g's it still should be able to handle upwards of 50g's under positive load. Here is a look of how the center section looks from the front. Next I have to start to blend the center section to the wing and build the outlet tube/linkage housing. A few photos to show how the blending progressed. At this point two thirds of the center section has been blended, so now it is on to making up the torque rods for the elevons. After I have the torque rods finished I can move on to building the linkage tunnel/cooling exit and tail cone section. I have got to have this all ready to go before I can blend in the last several inches of the center section and the wing, as well as the root section of the elevons. At this point the major part of the construction is finished leaving only the wingletts and elevons yet to be built up. Even though a lot of sanding and filling needs to be done I think the airframe is getting to the point that you can see it's final shape starting to emerge.


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That wasn't a crash, it was just a "hard landing".
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Old 03-28-2012, 12:06 PM   #3
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Doesn't look much like a glider to me, but it should be one hot delta. With 1.5KW at that weight, you should see some blazing speeds. Looking forward to the first flight to see how this thing performs.

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Old 03-29-2012, 02:33 AM   #4
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mred, Your right it's not a glider but hope it will qualify as a "Hi performance" airframe, I had asked Don about where to post the build, and he said that either here or the delta forum was appropriate. I hope your right about the blazing speed part it ought to be quick if I can keep the weight down. As far as power the motor is rated at 1.5 Kw burst I am hoping with the cooling system I am using that I could push that up another 10 or 15 %. This same plane has gone past 200 Mph with a FAI Nelson engine I hope to be able to match that.
A bit of progress ...
While the first picture may not look like much, it is a part I have needed for some time, these are the torque rods for the elevons. Now all I have to do is make up the top of the control horns that the push rods go through and I can proceed with enclosing them in the cooling duct inlet. I have got to build the torque rods into the trailing part of the wing and cooling duct once they are mounted to the trailing edge of the wing in their mounting tubes.
I gone around and around several times on how I was going to enclose the control linkages. I was going to either use blisters, or scrap the winglets and go back to the two fins mounted near the center of the fuselage so I could use them as a canoe covers for the elevon linkage. I really wanted to use the winglets over the fins for the reduction in interference drag and a couple of other reasons. Because the control horn have got to fit inside the cooling duct they are a bit shorter than I would like. Because I can't give the servos the mechanical advantage I would like, I had to go to a stronger servo than I would have used. Just to throw a bit higher level of difficulty into the control linkage I am using a pushrods in what would normally be a pull/pull configuration so I have push/pull action on the elevon torque rods. (see sketch- It shows the torque rods in the cooling exit)
I have also redesigned the winglets using a 3/16ths thick built up construction rather than the 1/8 slab construction, as well elongating them, and raking them a bit more. Doing this I reduced the overall frontal area by about 3/8ths of a square inch by lowering their profile by just over an inch. Because of the swept wingtips on this plane I also was able to move them back from the neutral point by 2 inches.
Well now back to building instead of drawing...


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That wasn't a crash, it was just a "hard landing".
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Old 03-31-2012, 11:04 PM   #5
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I still think with 1.5KW pulling that thing it is going to be fast. Just hope it keeps all the parts on while flying. I'm not quite sure about those ducts you have on it as to what they are doing and how they are plumed, but it looks good. It looks a little like there is some cross bracing on the inside that will mess up the air flow, but I could be wrong on that. All in all, it looks good. When are you planning to fly that thing?? I would really love to hear a report on it. From the look of it, it should be well over 100mph, don't know about 200mph though.

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Old 04-08-2012, 04:15 PM   #6
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Sorry for the delay in answering your post, for some reason I am not getting notifications...
The ducts are for the cooling of the electronics and hopefully converting waste heat from them into thrust. If I can keep the weight to the 2 lb limit I have set; on a four cell with a 5.25X6.25 prop 200mph should be obtainable.
Hopefully in a month or two it will be in the air.

The first plane I built with a similar power package has only 2 flights on it and I am trying to match the prop to the airframe and motor.
Here is the second flight never got the prop out of stall.
http://www.youtube.com/watch?v=MmF5kgUkEgQ

That wasn't a crash, it was just a "hard landing".
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Old 04-08-2012, 11:19 PM   #7
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That motor sounded like it was screaming it's poor little heart out. It looked like it had reached it's max speed after a few seconds. How can you tell the prop is still stalled?

It also looked like you were in and out of the clouds for a second there. If that thing never got up to full speed, then I don't see how it ever could. With the prop stalled at that kind of speed, I think maybe there was to much pitch on it to break the stall. I like your launcher too. That thing is pretty cool. Sure beats trying to throw it by hand.

You going to take it to SEFF any times soon?? They have a segment for all you speed demons that get a kick out of going super fast. I like to watch, but I am way to old to even come close to keeping up with one of those things. I think my reflexes would be about 10 seconds behind one of those, well, maybe just 5 seconds, but I think that is still to slow.

That looks like a strange contrail you had up there that day. It almost looks like a pulsed engine of some kind.

Ed
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Old 04-09-2012, 01:18 AM   #8
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It was turning 29700 rpm a god portion of the first few passes, man it sounded mean and nasty. There are a couple of indicators that it was stalled, one it didn't get fast enough so you could hear the Doppler effect like during the maiden, and two the current draw was much lower than it should have been on the order of 20 amps or so. That was the second flight and it was on a 5 X5.5 the first flight the maiden was done on a 6X5 and drew almost 400 watts more than the second. Trying to toss that thing into the air like I did on the maiden is not all that good of a method of launch hence the catapult you saw on the second flight. It took me the better part of three months to design and build the catapult, lots of trial and error and testing before the final version you saw, but it was kinda fun...
I'd like to go to see the SEFF sometimes soon but probably not until next year at the earliest. I'd like to go to the Carolina speed rally as well but that to has to wait.
As far as flying the thing I had one of the best pilots in our club fly it, I'm the guy working the launcher, my reactions aren't all that good either but he said during the second flight it was a real cat, it was a real handful the first time out. The elevator response was way too touchy if you look at the video of the first flight you'll see what I mean it was only his skill that got it back down.
Maiden flight video:

Yea we noticed the contrail during the flight and it wasn't there at the start but was there right after the first pass, almost like it came out of nowhere...

That wasn't a crash, it was just a "hard landing".
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Old 04-09-2012, 04:32 AM   #9
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I was watching the guys at SEFF launching theirs and the ones that had the good easy launch had a lower skeg on it that they could get a good grip on. They also had rear motors, so the launch was motor off until it left their hands and then turn it on and go. Seemed to work great. It also made for a good skid to land on without ripping the bottom up. I can't go this year, but I am planning to go again next year.

I don't know is it is just me or what, but the first flight looked faster then the second. It sure wasn't as smooth though. I wish I could fly one of them again, but my reflexes are just to slow for them and while I could fly one as long as everything was going good, the second things went bad I would be way to far behind it. I'm also not one to let someone else have all the fun, so I'll just stick to my slower planes.

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Old 04-09-2012, 05:46 PM   #10
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Ed,
If things go bad with this type of airframe at high speed, even quick reflexes may not be enough! On the plus side it would be over very fast. But I feel as you do about the need for quick reflexes, you notice I wasn't flying it...
Sorry for going off topic guys but I just wanted to show an example of the power train that is going to be used in the "Screamin Demon" and it's potential.

I've had someone take a look at my selections of materials and proposed method for using the torque rods and the setup I am using should work. Because of the limitations in the dimensions of the control horns for the torque rods I had to go with 100 oz servos for this plane. I have just finished cutting out the pockets for mounting the servos. I really wish I had done this before I had the sheathing on but this part of the design was still in a state of flux until recently. Now having gotten that sorted out the build will start to progress again.
Here is how the servos are stuffed into the airframe...


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That wasn't a crash, it was just a "hard landing".
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Old 04-10-2012, 05:49 PM   #11
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That wasn't a crash, it was just a "hard landing". He says as he digs the remains out of a 3 foot creator.

One question. How are you going to get to the screws that hold the servos in? It's looking good so far, with that one exception. I think this is going to be a real mover after you get it finished. Glad I don't have to fly it. I think 100oz servos should work great. Isn't it great to have all these choices now days? When do you plane on having this finished? Looks like you could have it ready for flight in 2 or 3 weeks, unless you build like me, then it may be 2 or 3 months. I'm looking forward to seeing the video of this one flying.

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Old 04-11-2012, 03:12 AM   #12
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I have pulled parts out of a crater before, or just thrown dirt in to finish filling the hole.
I am going to use cap head screws with allen heads to mount the servos, along with some rtv as adhesive and to seal the cavity. There isn't enough room to get in there with a screwdriver. I may have to do the same for the servo horn screw as well, with the 100 oz servos it's pretty tight in there. As it was I had to use a shoehorn to get them to fit. Yes it's nice to have all the option today as far as equipment, in the past I used boost tabs for large surfaces that I could not drive with stock servos.
As far as the time it's going to take to finish I'd hate to have to set it in stone but giving my lack of progress the past couple of weeks it will probably be a month or so. Once I get the control surface linkages all installed I can finish building the cooling duct and finish up the blending. Building the cooling duct is going to be a bit like "building the bottle around the ship" if you know what I mean. After the cooling duct and blending is done the elevons and fins are the last of the "building". After that it just doing the finish and installing the motor, ESC and rx.
I can see the light at the end of the tunnel, hopefully it's not not a train...

That wasn't a crash, it was just a "hard landing".
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Old 04-12-2012, 02:17 AM   #13
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I can relate to the crater and pieces laying all over the place. I was thinking that cap head screws would be the best to use there. Make it a little easier to get them in and out. I never give a hard fast finish date. Mine always run over that, so I just gave up. I really like the looks of this one from what I can see. I am looking forward to seeing it fly.

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Old 04-12-2012, 02:31 PM   #14
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Thanks Ed!
Hopefully I'll get some more done on it in the next couple if days, I am looking forward to seeing how all of the modifications I have done to this works out...

Oh by the way, the hard landing thing is something the Wrights used to say, they personally never referred to an accident as a crash, they always called them hard landings, I liked that...

That wasn't a crash, it was just a "hard landing".
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Old 04-12-2012, 09:52 PM   #15
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Well, that is true. it's just that some are harder then others. I normally have a pretty good landing or a really hard one. I never seem to get the ones in between. As long as you do a little every night, sooner or later you will finish it............

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Old 04-13-2012, 02:00 AM   #16
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I prefer the ones that don't involve repairs!
Well got a bit done tonight the elevons have been made up as well as a better rendition of the cooling duct and exit.


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Old 04-24-2012, 08:16 PM   #17
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A bit of progress...
I finished up the trailing edge of the wing fitting the tri-stock to it as in the original design (hinges will be used on that portion), and then made up the mounting and housing portion of the trailing edge where the torque rods are going. I then fitted the left elevon and fitted it to the torque rod. Here is a couple of photos to show what little progress I have made. The first shot shows the torque rod and brass bushings for them, The second photo shows the left elevon fitted and in place.
Now on to fitting the right elevon and making the last major structural modification before installing the torque rods permanently into the airframe. The torque rods and linkages need to be finished before I add the last of the tail structure that makes up the cooling duct, cooling exit and blending of the evelon roots into it.


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Old 05-05-2012, 06:16 AM   #18
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I have started on the blending of the root of the elevons into the main fuselage. While it all need quite a bit more sanding and fitting before the root blends are completely done, I need to get these parts ready as they are also used to enclose the torque rods bushings and will go on when I install the torque rods. I have also started fitting the cooling duct (just sitting between the root blends to give you an idea of how it going to look) and exit nozzle, making up the nozzle is going to be a bit tricky. I am also working on the last of the fitting needed for the control linkage
So what do you guys thing of the elevon mods?


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That wasn't a crash, it was just a "hard landing".
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Old 05-09-2012, 03:46 AM   #19
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I think those elevons look great. This is getting to be a right pretty plane and I am really looking forward to seeing it finished. Make sure you take plenty of pictures before you fly it. I would love to see a movie of it flying too. For some reason, like you I am not getting notified of postings here and forgot to check up on you for awhile. It is looking great though.

Ed
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Old 05-09-2012, 10:17 PM   #20
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Thanks Ed,
I hope that the modifications I made won't adversely effect the overall performance. I just felt with the enlarged cord area I had to use on the elevons, because of shorting up of the span, would tend to make it a bit more pitch sensitive. I am hoping the swept wingtips along with the new tail configuration will dampen the elevator response just enough to keep it from being too pitch sensitive at speed.
Right now I have the torque rods bonded to the airframe and am setting up the laser so I can get the root blending attached to the airframe at least close to straight.
I will try to keep getting some photos as I go along and when it's finished, and you have to know I'll video at least a couple of the flights just to see how it performs...
Regards
Paul
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Old 05-09-2012, 10:47 PM   #21
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I always set up a three way switch for rates and use 100%, 75%, and 50% just in case I need to cut the rates down on something. That way I don't have to worry about it getting away from me because of high rates. I like to use triple rates on mine, but duel rates is fine too in most cases. Beats getting high rates and not being able to control it. At slower speeds you may need the high rates, but the faster you go the more you need to cut down on them.

These new radios sure beat my last radio I had. That Pro Line had the smoothest sticks of any radio I ever had, but no computer and no duel rates. Kind of get spoiled using these now. I don't think I could ever go back to the old radios now after flying these computer radios. Love progress. It is hard to use those expo rates though. I was used to doing it myself and it's kind of ingrained, and every time I try it now they just get in my way.

Ed
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Old 05-10-2012, 07:09 PM   #22
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Ed,
I agree with you about the new radios. My first "RC" plane had only a one channel escapement for control. My best radio today is a 7 channel computer radio and it is light years ahead of anything I had used in the past. Wow, I did not know that there are radios equipped for triple rates I guess I should take a better look at the radios out there today...
This modification I am using for the tail of this plane came about for a couple of reasons. The first reason, as I have mentioned, is to hopefully tame the pitch issues I know that the elevator response is going to be a bit touchy with the shape and style of the elevons (or at least I anticipate that it may be an issue).
The second reason is just a theory of mine relating to wake drag. Looking at what information and photos that are available for some of the new advanced concept aircraft I suspect that some of new airframes are addressing that particular issue in a few different ways. One of the trends I have seen is for this type of configuration as far as the aft portion of the airframe. My next version of the Stingray is going to have this incorporated as well and I wanted to see how it affects this plane's performance if I added it to the stock airframe. The next version of the Stingray is going to be a full on BWB, with separate control surfaces and servos for both the elevators and ailerons. While the first version is now pretty good using dual rates and expo there is lots of room for improvement.
After having gotten pulled away from the build yesterday just as I was about to install the root blending to the airframe I am going to try to get onto that now.
Thanks for taking the time to pass along those tidbits, of information it is helpful to know how other people address these issues, it serves as a reminder of how I tend to over complicate designs at times...

That wasn't a crash, it was just a "hard landing".
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Old 05-11-2012, 05:14 AM   #23
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I started out with the old Bonner single channel if you remember that one. My first multi was the Controlair and that last good radio I had before I dropped out for awhile was my Pro Line. I now have a JR 9303 and an Airtronics SD-10G. The JR has triple rates on ONE switch if you want to put all three surfaces on it so they all go together, or duel rates on separate switches. My SD-10G is ALL triple switches and you can assign ANY function to ANY switch. You wouldn't believe the programing power of that SD-10G radio unless you read the manual. Talk about a fantastic radio. All kinds of flight modes possible with that one. Best radio on the market as far as I am concerned.

On that drag of your plane, I wouldn't get all involved on trying to get rid of every little bit of drag. If you were going out for the world record, that would be different, but there comes a point of diminishing returns. For a LOT of design work you get very small returns. I would just worry about the big stuff and not worry about the small stuff for right now. Get it flying and then if you need to get every last mph out of it build a MK II if it is worth it.

So far it is looking great. It looks like one of those designs that just look right to begin with. I am looking forward to seeing this one fly. I wish I still had the reflexes to fly planes like this. I hate building a plane that I can't fly. I'm just one of those people that has to get his hands on everything I build, even if I have to have someone else fly it to check it out first.

It seems kind of strange. I had to get a guy to check out my last plane for me before I felt like flying it, but once I was the guy that everyone came to to check out their new planes. Times and age sure do change things.

Ed
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Old 05-11-2012, 12:29 PM   #24
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Ed,
I do recall the Bonner systems that is what my first setup, it was given to me by an older guy that got me into rc when I was a kid. I went from that to a heathkit radio and then a Kraft before girls, cars and full scale airplanes distracted me from the hobby. It wasn't until 2000 or so I got back into the hobby and the first radio I got when I got back into the hobby was a Hitech Aurora 7 channel. A friend that I worked with at the paper told me about the one he had and that's how I ended up with that particular radio. I also have a basic Futaba 5 ch 2.4 Ghz that while it is very limited is usable. The new JR's or Airtronics are something I'd like to get when I have the cash but for now what I have is going to have to suffice.
As far as my concern about drag...
Given the present power system I am using, I don't expect to achieve a world record, but it is something I do want to try for. Yea, I know pretty nuts, but we all need to set some sort of goal and that's one I'd like to try for. The stingray and this are my first fledgling steps in that direction. You've discovered my secret goals with all of this, lol. Given my health lifting balsa is about all I'm good for so I am trying to have some fun with it while I can.
While I may fly these at fairly normal speeds I doubt that I will fly them that much flat out the stress may be a bit much for me. I love to build and it is one of the few things I can still do, even if my reflexes aren't good enough to fly it flat out I get a kick out of seeing it being put through it paces. I had gotten back into RC to test a full scale design I wanted to build but my heart condition put an end to my being able to fly full scale, so I have to stick to settling for the R/C ones. Like I told my wife it's good therapy and it keeps me from dwelling on my health. The challenge of building a really high performance airframe keeps me from dwelling on what I can't do, and like I said I love to build. There are a couple of other guys in my club that are into building and it seems of late we have inspired a lot of the new guys to try their hand at it as well. Don't get me wrong ARF's are still the majority at the field but you see quite a few home brewed airframes as well nowadays. The fact that we have members like Jack and Ted Patrolia in our club and their support to anyone that's into building helps a lot I think.

That wasn't a crash, it was just a "hard landing".
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Old 05-11-2012, 06:21 PM   #25
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Well, I was just about to hit the send key when my power blinked and I lost everything. Don't know what is going on, but the power went out for about 10 seconds in my whole house, so I lost everything I was getting ready to send. That being the case, I'll just say, hope you make it with the world speed record and best of luck to you. Nothing in the world wrong with attempting the record. That's what it's there for, to break. Best wishes and hope you make it.

Ed
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