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Foamboard F-22 EDF

Almost there! Basic colors are on (two different kinds of primer). Now I just need to come up with some pseudo-markings and do some sort of hatch latch. Not perfect by any measure, but it kinda looks like a Raptor. :)

Chris

PS: Ignore the naked Mamba in the background, it just got de-stickerfied in preparation for some custom vinyl.
Looks alot like a Raptor (y)(y). Going to hold my latch down with a popsicle stick on front end to slide in and back end gets held down with a magnet.
 

JustPlaneChris

Well-known member
Looks alot like a Raptor (y)(y). Going to hold my latch down with a popsicle stick on front end to slide in and back end gets held down with a magnet.
That's my plan as well. I really don't want to add any more weight up front (magnet) but it's kinda necessary.
Mine seems to be a bit porky, no doubt due to my 3D printed ducting and too much paint. I'm sitting at 15.5 oz / 439 g without battery. More than I'd hoped, but I'm sure it'll fly fine.

Chris
 

The Hangar

Fly harder!
Mentor
Almost there! Basic colors are on (two different kinds of primer). Now I just need to come up with some pseudo-markings and do some sort of hatch latch. Not perfect by any measure, but it kinda looks like a Raptor. :)

Chris

PS: Ignore the naked Mamba in the background, it just got de-stickerfied in preparation for some custom vinyl.
How are you liking the mamba? I just put the 4s setup in mine and that gave it a bit more power, and I have a 12x6 prop on order to try out. Did you mess with the aura tune at all?
 

JustPlaneChris

Well-known member
I'm only 3 packs in, but so far it looks like it'll be fun! Mine's the G2, running 6S. Power is ridiculous. Haven't messed with the Aura tune yet, it seems pretty well sorted right out of the box.

Chris
 

JustPlaneChris

Well-known member
Well, that ended poorly. :cautious:

First toss skipped off the runway, then got flying but it clearly was either nose heavy or had insufficient elevator throw, because full up wouldn't keep the nose up. A very fast sliding landing was made in the grass with no damage.

I added about 1/8" up elevator, and taped some weight on the aft end. As near as I can tell, the CG was then where the plans showed (which seems about 35mm aft of the LE of the wing at the root). EDIT: I don't have the full size plans to verify for sure, but now that I enlarge the PDF and do some measuring, it looks like the CG should be more like 50mm aft of the LE! No wonder it lawn darted!

Second toss started OK, but soon I realized that once again full up wasn't enough to keep the nose up. This time I had to turn to avoid trees, and as soon as I banked the nose dropped and that's all she wrote. Spectacular cartwheel, the battery plowed through my RX (write-off) and I spent the next 10 minutes in 95F heat wandering around in tall stickery weeds looking for the battery. :mad:

At this point I don't know whether to rebuild or not. There's no way to make the nose lighter, and there's no way to get the battery pack further aft. The fan really needs to be mounted further aft, but that's a complete re-design. I suppose I could add tail weight till it flies right, but how many more crashes will it take before that is achieved? :unsure:


Chris
 

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That sucks Chris,

If it were me I'd repair it, at some tail weight to get the c of g where you think it should be, as a bit more throw and give it a another shot. Not much to lose. If you end up loving how it fits then you could rebuild it with the fan a little farther back.

Cheers,
Brian
 

JustPlaneChris

Well-known member
Thanks for the encouragement, guys! I've already started the repairs. As you say, it won't be too hard to graft a new nose on it. As for adding tail weight, I'm sketching on a way to add stabilators. It needs tail weight, so why not make it functional? As for the rest of it, it seemed OK. Roll trim was fine, and it had gobs of power (just about 1:1 thrust to weight).

I have a few other ideas to incorporate on the rebuild, so it may take a while. I'll update when I have something to show. :)

Chris
 

JustPlaneChris

Well-known member
I've been pecking away at the rebuild, in my spare time. The first thing I did was cut away all the smashed areas, and then decided (perhaps unwisely) to strip all the paper. My logic being that my paint job was garbage, and there were various wrinkles. More on the paper stripping later...

I also wasn't happy with my pushrod routing, so I opened up the servo area and pulled that out. While I had it that far apart, I went ahead and drew up a stabilator mechanism that uses 3mm carbon rod to pivot the stabilizers. Retention will be handled by the pushrod (simple, and OK for a small model like this).

It's coming together, but of course now it looks worse than it did right after the crash! It'll get better.

Oh, about that paper: I did several test pieces, trying various types of paper and adhesive to try and replicate the stiffness and lightness of the DTFB. To my surprise, it's really hard to beat! The closest I've come to the original weight and stiffness is by using regular typing paper and a 3:1 mixture of white glue and WBPU. It's not ideal, since it won't drape well over curves like the newsprint-type paper I wanted to use. But... the stiffness will likely be worth it We'll see. I may use a combination of both types, reserving the newsprint for the curvy areas.

Onward!

Chris
 

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Monte.C

Legendary member
I've been pecking away at the rebuild, in my spare time. The first thing I did was cut away all the smashed areas, and then decided (perhaps unwisely) to strip all the paper. My logic being that my paint job was garbage, and there were various wrinkles. More on the paper stripping later...

I also wasn't happy with my pushrod routing, so I opened up the servo area and pulled that out. While I had it that far apart, I went ahead and drew up a stabilator mechanism that uses 3mm carbon rod to pivot the stabilizers. Retention will be handled by the pushrod (simple, and OK for a small model like this).

It's coming together, but of course now it looks worse than it did right after the crash! It'll get better.

Oh, about that paper: I did several test pieces, trying various types of paper and adhesive to try and replicate the stiffness and lightness of the DTFB. To my surprise, it's really hard to beat! The closest I've come to the original weight and stiffness is by using regular typing paper and a 3:1 mixture of white glue and WBPU. It's not ideal, since it won't drape well over curves like the newsprint-type paper I wanted to use. But... the stiffness will likely be worth it We'll see. I may use a combination of both types, reserving the newsprint for the curvy areas.

Onward!

Chris
Be careful - When we were younger I had a friend who bought a jeep. He decided to take it all apart - the whole thing - because he's an idiot. Of course he didn't know how to put it back together again, so he sold the entire pile of parts right off his garage floor. :rolleyes::LOL:

Hey I found the paper I stripped off white foam was of lesser quality (but probably lighter) than fairly good quality printer paper.
 

JustPlaneChris

Well-known member
Repairs are coming along! I still need to route the pushrod for the right stabilator, then close up the holes over the servos. Once that is done, it'll be ready for re-skinning. Oh, and of course I need to make a canopy! This time it's going to be carved from foam. The new nose section was created using a side and top view cut from foam board, then skinned with individual sheets of foam. Basically like old-school balsa construction except with foam! :)

I'm thinking I will cover the wings and fins with printer paper, and the forward fuselage (all the curvy bits) in 1.5oz fiberglass cloth. In both cases, the adhesive will be a 50/50 mix of Elmer's School Glue and WBPU. Incidentally, the School Glue is better than regular Elmer's glue because it dries to a harder consistency. Regular Elmer's stays rubbery.

Chris
 

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Repairs are coming along! I still need to route the pushrod for the right stabilator, then close up the holes over the servos. Once that is done, it'll be ready for re-skinning. Oh, and of course I need to make a canopy! This time it's going to be carved from foam. The new nose section was created using a side and top view cut from foam board, then skinned with individual sheets of foam. Basically like old-school balsa construction except with foam! :)

I'm thinking I will cover the wings and fins with printer paper, and the forward fuselage (all the curvy bits) in 1.5oz fiberglass cloth. In both cases, the adhesive will be a 50/50 mix of Elmer's School Glue and WBPU. Incidentally, the School Glue is better than regular Elmer's glue because it dries to a harder consistency. Regular Elmer's stays rubbery.

Chris
There ya go, Great repair work!
 

Monte.C

Legendary member
Repairs are coming along! I still need to route the pushrod for the right stabilator, then close up the holes over the servos. Once that is done, it'll be ready for re-skinning. Oh, and of course I need to make a canopy! This time it's going to be carved from foam. The new nose section was created using a side and top view cut from foam board, then skinned with individual sheets of foam. Basically like old-school balsa construction except with foam! :)

I'm thinking I will cover the wings and fins with printer paper, and the forward fuselage (all the curvy bits) in 1.5oz fiberglass cloth. In both cases, the adhesive will be a 50/50 mix of Elmer's School Glue and WBPU. Incidentally, the School Glue is better than regular Elmer's glue because it dries to a harder consistency. Regular Elmer's stays rubbery.

Chris
Amazing.
 

JustPlaneChris

Well-known member
Thanks! One of the benefits of building using this method is you get to carve, sand, and spackle it until it looks good. Believe me, it looked pretty bad when I first glued it all together! S&S (Sandpaper and Spackle) hides a multitude of sins. LOL

Chris