F22 First EPP Foamie

[akent]

Gabe, that F22 is the RC Powers version that is built from brittle Depron foam.

I actually bought those plans quite a while ago and built up an airframe. It is a more difficult build and mine didn't end up perfectly straight, so I never powered it.

The one we built here is a super simple build with free plans, and is made from EPP foam. I don't remember anyone doing a KF mod to this one. That is usually more common with the depron as it's thinner. A KF addition to this 9mm stuff would be pretty thick at 18mm.

Thanks for the link, though! The RC Powers version does look nice.
I may build another one with more patience one of these days. Nah, probably not, as I love this super simple one! I almost have my third airframe done with the Grayson motor! I should have it flying this afternoon. Well, ready to fly as it's drizzling outside now.
Kent

[BTCat]

19K, you don't need any support from me. You are among the masters, in my book

On the KF, the only way I see it working is with a morphidite combo of Depron over EPP or even Dollar Tree foam over EPP. The Dep. can be beveled with sand paper and a step support can be cut out at any height and glued to the trailing edge of the KF top piece. It would add some rigidity but would also make it a more fragile bird.

From what I am reading, the advantage of the KF (Top 50%) would be in stall speed, slow speed, high alpha etc. but it is at a notable disadvantage in the top speed category due to the increased drag. This may or may not be overruled by the improved rigidity. Interesting mode idea, though

[19000rpm]

With the battery moved back and max throw on the elevons and 10 clicks of "up" Tx trim she flies straight as an arrow up to about 60-70% throttle. Max the throttle and it goes nose down slightly.

Aerobatics are improving. High Alpha went up a notch or two. I'll slide the battery back just a bit more.

I'm thinking my theory about the flex in the wing causing both the nose down attitude and speed loss could be correct. The more air over the wing produced by both speed and, more likely, the prop wash is bending the back half of the wing down like down elevon would do. I'm going to look at some ways to fix the flexing.

I'd "guess" the speed to be around 68 now. I does seem faster than it did before. Eliminating the elevon trim by moving the battery back further and eliminating or reducing the flexing might add a mile an hour or two.

I can't wait to hear Kent's report on his new one.

[19000rpm]

I've spent quite a bit of time trying to find a way to make the airframe a bit stiffer without taking it all apart. The main weakness is in the area of the prop slot. Nothing seems to work so I'll leave it the way it is.

In a new airframe I'd make the prop slot a bit smaller and add CF along the skids going right into the fuse closely around the prop slot.

[Gabe]

Very slick. I'm into to simple stuff!

[19000rpm]

Apr 14, 2010 5:59:57 GMT -6 Gabe said:

Very slick. I'm into to simple stuff!

I like stuff simple too. Sometimes I get forced into something a little complicated to just make things work. But, believe me, I'm not having that much fun doing it. ;D

[akent]

I have some EPP news.
A while back, I ordered some new EPP from Grayson. This time some 1.9# stuff. This stuff is considerably more rigid!
This 1.9# is nowhere near as rigid as depron, but it's probably twice as rigid as the 1.3# stuff! I think the weight numbers are for a cubic foot, so it's not much. It's hard for me to tell the difference by feel.

I know over on the F22 thread at RCGroups they only use 1.3# that I read. That's why I bought that to begin with. I think they are after lightness mostly. I think if you want to go fast, this heavier more rigid stuff just might be the ticket. I'll soon know how it flies. I hope in the next few days.

I still don't have the new F22 completely finished (need to finish up the electronics).

I also noticed that around the prop slot is the most flex. I built the new one with almost the same CF configuration of my original one, but I put the outside angled CF on the bottom this time. It has far less flex around the slot.
And the elevons are far more rigid. I don't think I'll even put CF there to begin with.
Kent

[akent]

Here's a picture of how I did the CF on the bottom.
Note that the leading edge flat CF goes all the way to the fuselage.
This is pretty darned rigid, but a lot of that is the new EPP.

[Solitaire]

I bought the 1.9 weight stuff too, Kent. I already have a 1.3 weight plane I got from HC and wanted something a bit stiffer and less porous.

We'll see how it all works out when I get into the build.

[19000rpm]

Glad you ordered the 1.9 Kent. It sounds like the 1.9 might provide enough extra ridgidity and reduce the amount of CF required. That would be neat.

I haven't been able to fly all week with the high winds and rain. today and tomorrow look pretty iffy too. Maybe Sat.

I took the time to catch up on organizing stuff and when I looked closely at the F22, I noticed that the CF tubes I put on top of the wing had pulled loose at the center on both sides of the wing. That tells me that there was a lot of flexing in that area and that the tubes were doing their job until they pulled away. I doubled the amount of CA I originally used when I glued the tubes back on.

Hope you guys get your F22's in the air soon so we can compare notes.

I'm ready to build another fighter out of this stuff. Any suggestions?

[akent]

I hear you on the weather. Here, it's been mostly either too windy or raining.
Ugh.

I have the New F22 ready to fly. I mounted the servos a lot closer to the elevons this time. There is virtually zero slop due to bending or anything else. It helps the CG, too, being farther back.

This one certainly weighs more than the earlier ones.
The new one's AUW is 14.3 ounces with a 1000ma 3s battery!!!
The original one weighs 11.6 ounces with the same battery.

Wow, it gained some weight! I know the motor, ESC and foam all weigh more, but I'm a little shocked it's that much more.

Man, I can't wait to fly it!
Kent

[akent]

Another EPP fighter, 19k?

I haven't looked to see if any others are being built out of EPP over at the other place.

Of course, you could build up one of those uber fast ones that Tony turned us onto!
Kent

[19000rpm]

That's almost an ounce more than mine weighs and you used less CF. Must be the 1.9 stock.

It looks like those guys at foam fighters are glassing over the EPP. I think that's great, but I'd like to stick closer to a minimum build.

25 mph today, gusts +30. 15-25 over night doesn't indicate a good day tomorrow.

[akent]

I hear you on the simpler builds.
That's the main reason I love this F22. Very few parts and it's so easy to put together!

You should see all the parts for the RCPowers F22. There's a LOT. And you have to trim a number of them as you put it together for them to fit right. It takes a lot of time. But it does look pretty cool for a foamie.

Please post if you figure out what you want to build. I'll want to build a different type too!

Oh, and one ounce difference is surely the foam. Actually only an ounce is not bad at all, given the stiffness difference. I don't think I would ever build a 3d machine from this stuff, but for these jets, I think it's likely the ticket. If I could just fly this thing!

Our winds are light right now, but it's raining much of the time! Rain for the next several days. I hope there is a lull in the weather for all of us!

Kent

[19000rpm]

I had forgotten I've added more CF since I weighed it. I'm probably up to your F22's weight. And, you're right; the weight isn't an issue.

I built the RCPowers F117, so I know what you're talking about. They're nice looking and I didn't mind the build so much, it was the rebuilding that got tedious. It flew great, but it was really fragile. 1 out of 6 landings caused some damage. Particularly to the nose; which I even had extra carbon on. The last flight, a little gust caught it just before touch down and buried the nose, snapped the nose off, flipped it over and broke almost everything. I got tired of fixing it.

So far nothing has broken on the F22 except the CF I added coming loose on the top of the wing. And I'm fairly sure it didn't come loose in a landing; it came loose in flight. Either way, that was my fault for putting too little CA on it.

I think I'd try a 3D plane with the 1.9.

Maybe an F18 for the next fighter.

I haven't flown since last Sunday. That's 5 days. I don't think I missed many more days of flying even in the dead of winter.

We've got sunny skies for the next few days and the winds are supposed to be down to 10-15 or so. I wouldn't call it ideal "testing" weather, but it sure is great "flying" weather.

Hope the weather clears up for you there soon.