Astron Invader 2.5x upscale R/C

Keyword is delamination. Paper separates from foam core.

As far as I can reconstruct the sequence of events from debris, canards pull skin off vertical stabilizers' inside surfaces, then bottom surface off top wing, then top wing disintegrates, losing both its skins. Motor is still burning and folds the canard in half separating right canard surface.

Bottom wing has clear tape on its leading edge and survives intact. This wing had developed creases on the outboard left section (you can see them running 45 degrees back form rudder to wingtip) and I used tape in hope of restoring rigidity to this panel.

Interestingly, most glue lines survive this disintegration. If I can keep skins on the foamboard, this thing might hold together. This analysis leaves me wondering if taping ALL leading edges may prevent such delamination and make flight survivable.

Here's video by David Springsteen. Accident flight is at 3:47 in this video--preceding footage is of two successful flights of this glider.

[video=youtube;fihOwMpots4]https://www.youtube.com/watch?feature=player_detailpage&v=fihOwMpots4#t=229[/video]
https://www.youtube.com/watch?feature=player_detailpage&v=fihOwMpots4#t=229

Generally, delamination is something I almost never see, since I DO tape/round the LEs of wings and such. Placing like 1/8" round dowelling over the LE and taping over that gives strength, lower drag, and also keeps the LE paper from delamming off the foam.

Reckon you should do another and tape/dowel the critical LE's. Perhaps use a D12 first, then a BP E motor, before the AP big hitters.

I bought a mega Red Baron and figured I would build it stock. I was thinking that maybe later I could build a second mega Red Baron out of foam board and use R/C, but this shred is giving me second thoughts.

My R/C Mega Baron has been a super-reliable performer and crowd pleaser.

I have flown it on D12 and F15, as well as staging D12-D12 and even D12-D12-D11P. It gets pretty small with staging.

Ari.

I built a new Foamboard Baron, and this time I taped all edges. Without any particular thought (except that it's $2 cheaper) I used white foamboard instead of red/yellow like last time. This stuff is entirely different! It's heavier, the cardstock is thicker and refuses to delaminate if I pull it by hand. Color paper just peels off if I lift a corner, but this white paper tears rather than separate from foam. As a point of comparison, the same size piece of color board weighs 5.0g while white is 7.0 (what's with round numbers?) With all this, it seemed like taping edges may be redundant, but I did anyway. It came out heavier at 120g, and then needed 15g of led shot in the nose for a total of 135g. Red/yellow baron balanced without any ballast.

The White Baron flew today on a D12-3. Considering the excitement of previous flight, this one is boring and uneventful. Nex5, E15-4.

Ari.

[video=youtube;pO2Zf82bDMg]https://www.youtube.com/watch?v=pO2Zf82bDMg[/video]
https://www.youtube.com/watch?v=pO2Zf82bDMg

iter said:

I think I'm going to try a different planform configuration on my next glider. I might try something wedge-shape like Jet-Freak, where CG is closer to 50% root chord rather than 25% in a disk.

Click to expand...

I flew this one today also. I tried to fly it last Saturday at Moffett, but it got stuck on the rail (like the original Invader in this thread). I redid the rail guides and flew it on an E9 today.

It's difficult to film while flying an R/C model. I taped a keychain camera to my hat. It's the choice between this poor quality video and no video at all :=)

Ari.

[video=youtube;f4Wx_9tluaQ]https://www.youtube.com/watch?v=f4Wx_9tluaQ[/video]
https://www.youtube.com/watch?v=f4Wx_9tluaQ

That 'Wedgie' wing planform looks nearly *exactly* like the old 'Astron' planform I've been using for nearly thirty years in larger gliders!

Glad to see you got a foamy Jenny up and doing something as well!

Yeah, I'm looking for encouragement to build a larger version. I'm thinking of pink XPS insulation foam.

Maybe I call it Have Pink.

Ari.

iter said:

Yeah, I'm looking for encouragement to build a larger version. I'm thinking of pink XPS insulation foam.

Maybe I call it Have Pink.

Ari.

Click to expand...

You're laughing.

Ari.

I'm doing it. Have Pink deserves a separate thread. https://www.rocketryforum.com/showthread.php?64105-Have-Pink

Ari.

I flew the Wedgie on E15 today.

It survived pretty well. Closeups are before and after this flight. A couple of observations:

* Aerodynamic forces are completely manageable at this level of impulse; no sign of structural integrity compromise
* Aluminum tape seems to provide adequate heat shielding
* Elevons without aluminum tape suffer
* Heat area is longer than my anticipation (past trailing edge of elevons) but narrower (entirely within the width of tape)
* Tape adhesive's longevity is an open question

Ari.

Is the thrust line parallel to the wing or slightly up at the nose? I do know there are various qualities of tape available. The better ones are thicker and have better glue since they are meant to wrap heating ducts. The best are from HVAC suppliers. That looks like heat buckling, you might try short overlapping pieces.

I may have to build me one of those. :grin:


Richard

TheTellurian said:

That looks like heat buckling, you might try short overlapping pieces.

Click to expand...

Had to look that up. Yes, it does look like that. I wonder if you can elaborate on the effect short overlapping pieces may have on this buckling. Overlapping would introduce discontinuities in thickness and thermal capacity... but that's as far as my thermodynamics take me.

Ari.

The basic idea is that aluminum expands like crazy under high heat, thats why aluminum siding for example is attached through slots not holes so it can expand in the sun without buckling. The theory is the short pieces will not expand enough to buckle where a long piece attached at both ends has to go somewhere so it buckles. The idea is to layer the foil like the shingles on a roof with the first half attached to the wing and the second half floating free to expand. The second half should protect the next shingle [foil] under it, etc. Use talc or baby powder on the second half to neutralize the glue, it should not be attached to the next foil shingle, it wouild be back to square one if it is.

With the aerodynamics of this bird I don't think discontinuites in thickness is much of an issue and the more metal the more thermal capacity. The only weirdness might be finding one or more shingles lifted from venturi effect from the motor or stall eddies. I've not tried it so am talking in my hat, but its an idea and I'll admit there may be better solutions.


Richard

Oh! I get it now. I was thinking glue them one on top of the other. I like this idea. I need kind of aluminum post-it notes, with glue only on the top edge.

Ari.

Another idea is copper-clad FR4 (G10). I wonder if the copper would simply burn off or help dissipate the heat.

Ari.

G10 would be heavy though! Copper is just a bit better than aluminum but not alot. I might try an aluminum baking pan or oven liner, the type made from the heavier foil sometimes called tether metal. Its about 3-5 times thicker than foil tape. Fasten securely at the top edge but only attached through lengthwise slots along the sides, and nothing at the back. The slots will allow the metal to expand without buckling and it should [I hope] be strong enough not to deform from aerodynamic forces.


Richard

I found this when doing some googling on building an Invader clone, and I'd like to thank you guys for an awesome red ! Just joined this group, so I don't know if any of you are still active members, but if you are, thanks again !