F22 First EPP Foamie

[Gabe]

5-10 is bad for anything not related to me flying my planks.

[19000rpm]

Mar 20, 2010 20:13:24 GMT -6 Gabe said:

5-10 is bad for anything not related to me flying my planks.

Zero building yesterday. 100% flying.

[19000rpm]

More flying today. I did some building, but not on this baby. I swear I'm going to give it some attenion tomorrow...Maybe.

[akent]

[19000rpm]

Got a good couple of packs in today before the wind came up.

Back to the F22 build: Built the motor mount and modified the fuse a bit to fit around the motor mount and now the center spar of the fuse will go into and through the motor mount. I don't know what, if anything, this will do to the structural integrity of the fuse, but it shouldn't hurt anything. ;D

[19000rpm]

After reading Kent's report on the F22 vs Stryker thread I'm fairly convinced that the elevon is a weak point in this design for a high speed version.

I'm going to add two small, thin, strips of CF to the elevon, relatively equally spaced along the width of the elevon, on each side of the control horn on the bottom side.

I'll also be adding some additional adhesive to the servos and installing a support/guide for the control rods to dampen any oscillation.

I really believe that this plane should have some serious speed potential If I can just find and eliminate all the points that are susceptible to failure.

[akent]

It sounds like your motor mount method is superior to just gluing in a plywood plate like I did.

You are on the right track, I think! It could very well have been that the control rods started oscillating, too.

I think better than tape hinges might be needed, too. If I try again, I will be using some standard hinges in addition to the tape. I think the tape on the top should help with any high speed problems there, and strong CA hinges would keep them from pulling apart.

I also think I may have had the CG too far back. I should have moved it forward an inch or so, as speed and rearward CG's don't always work well. It may have become unstable just before the elevon failed.

I think if you were to apply speed in stages, it might be a good thing. Not just balls to the wall like I did. That was stupid in retrospect. You could possibly start to feel trouble and back off before it explodes.

I can't wait for you to fly yours!
Kent

[19000rpm]

Mar 23, 2010 10:07:39 GMT -6 akent said:

It sounds like your motor mount method is superior to just gluing in a plywood plate like I did.

You are on the right track, I think! It could very well have been that the control rods started oscillating, too.

I think better than tape hinges might be needed, too. If I try again, I will be using some standard hinges in addition to the tape. I think the tape on the top should help with any high speed problems there, and strong CA hinges would keep them from pulling apart.

I also think I may have had the CG too far back. I should have moved it forward an inch or so, as speed and rearward CG's don't always work well. It may have become unstable just before the elevon failed.

I think if you were to apply speed in stages, it might be a good thing. Not just balls to the wall like I did. That was stupid in retrospect. You could possibly start to feel trouble and back off before it explodes.

I can't wait for you to fly yours!
Kent

Kent, where would use say the correct CG is in inches from where the wing meets the fuse?

If I'm lucky enough to get this thing in the air for more than 30 ft. I'll probably keep it around half throttle or less. I'll land it in a minute or so and look for any signs of weakness. If it holds up to that, I'll go around at haf throttle and then make some relatively small adjustment in throttle, land, repeat the inspection and so on.

More things:
I'm taking a close look at hinges too. I read of a neat little hinge that can be made of nylon wire ties. I may add that too.

I'm also adding a 3mm tube of CF from the prop slot back to augment the CF going from the fuse to motor mount.

In all I think I'll end up with a stiffer and lighter bird than the Depron F117 I had. And, it was plenty quick.

Maybe I'll eventually get it to fully throttle and avoid an OH, OH moment...Or maybe not. Just like with the real thing before computers came along. ;D

[akent]

On mine, it measured 16" from the nose, which is where I have it for the original F22. This is good for 'normal' flying as well as moderate high alpha. I did try 17" with a 500ma battery and it REALLY liked high alpha on the original F22.

I'm thinking maybe 15" might have been a better place to start, with the hotrod.

I like all the additions you are doing with yours. If you really do get yours dialed in and going really fast, you should do a separate build thread on it!

I noticed at the site that Tony gave the link to that even with the EPP jet, they were using depron for all of the control surfaces. It is stiffer stuff.
Kent

[19000rpm]

Mar 23, 2010 14:08:22 GMT -6 akent said:

On mine, it measured 16" from the nose, which is where I have it for the original F22. This is good for 'normal' flying as well as moderate high alpha. I did try 17" with a 500ma battery and it REALLY liked high alpha on the original F22.

I'm thinking maybe 15" might have been a better place to start, with the hotrod.

I like all the additions you are doing with yours. If you really do get yours dialed in and going really fast, you should do a separate build thread on it!

I noticed at the site that Tony gave the link to that even with the EPP jet, they were using depron for all of the control surfaces. It is stiffer stuff.
Kent

I've got some 6mm Depron I could give a try. Wood might even be better. I think that's what they're using on the 140mph Strykers .

But first I'm going to try the reinforced EPP. I'd like to keep this an EPP and CF build. I'm a purist at heart. LOL

I'll do a seperate thread if all this works out. There's a way to go between here and there though. ;D

[19000rpm]

After looking at the elevons with the control horns (modified PKZ Corsair aileron horns) in position I decided to add a single 2mm tube of CF running, front to back, across the deepest part of the elevon instead of the two strips I had thought about earlier. This should give the added strength and stiffness required...I hope.

For the elevon system, I'm using cut down control rods from an Hobby Zone Super Cub and some Dubro Control rod guides to eliminate any control rod bend or possible oscillation from the elevons. The servos are Blue Bird 8g servos from Hobby King.

As another measure, to hopefully turn this floater into a speed demon, I'm going to add, 2 ea., 2mm CF rods from each of the vertical stabs into the wing.

In the end, I think this is going to be a pretty stiff airframe; without the brittleness of Depron and the impact friendly advantages afforded by EPP...Maybe the best of both worlds in foamie scratch builts.

[akent]

It's sounding great!
I can't wait to hear about you flying it!

[19000rpm]

It's done! At least I think so. My CG at 15-16" from the nose puts the battery under the cockpit which seems too far forward.

Too windy to fly it so I did a test glide indoors and it seemed to go in on its nose more than I would have guessed.

Elevons: I ended up using 2X2mm tubes in a "V" shape to strengthen each of the elevons. I did not modify the hinges on the elevons. I've got hinge tape on both sides and I think that should be enough...We'll see.

Vertical Stabs: Instead of CF tube, I was out, I used 2 ea. tooth picks in each stab through the wing for additional stiffness.

Skids and Fuse: I added strapping tape to the entire length of the skids and to the nose and underside of the fuse.

Electronics: Servos are mounted next to the skids with guides on the control rods. I installed 3" servo extensions to reach the Rx.

The 6100e Rx is mounted ahead of the motor mount with velcro and a velcro strap instead to a nylon tie for easier access. I did the Rx "suck test" at full throttle and the Rx did not move.

The ESC is velcroed and wired tied ahead of the Rx.

The 1300 battery is both velcroed and velcro strapped into place.

I'm happy with the finished plane. It looks good and I think the changes to the airframe make for a more solid plane. Hopefully a fast one too. The only thing that is of concern at this point is the CG.

The camera came last night and the battery is charging so I should have pics to post soon...Once I figure out how to do that. Help!

[akent]

It could be that 15" is too nose heavy. I just now moved my battery forward enough to get 15" and it is heavy feeling.
I have been flying it this week when the wind dies down at 16.5" and it feels really good.

I'll need to run out for a bit, but when I get back, I'll try to glide this some. I've never tried that.

You need to setup a photobucket account. That is probably the easiest. The files here are limited in size to less than most digitcal cameras can take these days.

You upload your pics to photobucket and when done, you can give it a caption. Once saved, there are some link areas below the picture. If you copy the IMG field and then paste it here, that's all you need to do. It already has the image header/trailer built in.
Kent

[akent]

I can't glide this thing!
It just always noses in or turns to the side or something.

I changed the CG from 15" back all the way to 17.5 and I can't get the thing to glide. If I give it power, then it's good! But it's way too windy to fly it today. 35mph gusts that just take you by surprise.

I was trying to glide in my garage.

Maybe it might be prudent to fly it with the forward CG and see how it feels in the air?

Kent