ZoomZoom-RCU

I'm in the process of building a WWI-esque biplane, roughly 24" span, but using some very light but pretty wood veneer as the building material. I've modified the design to be monocoque in both the wings and fuselage so the internal bracing is minimal and thereby weight reducing, which is crucial. The wings are tiger striped flame maple almost blonde in color, and the fuselage is a darker African Cherry, not quite as figured but still very pretty. Now I suppose I will have to take some photos for you-all, but anyway, I thought my foray from building in foam and switching to wood for this build would interest you guys. Powerplant is the trusty Surestart, but I have (as we always do) weight concerns. Wings are slighty undercambered, so as always with any design it is a balance of weight to power to drag to lift. Hope I've got it right for this one cause she's gorgeous.

ZZ.

combatpigg

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Howdy Zoom Zoom..!
Even though I'll take you word for it that you've built a great looking plane, pictures do add quite a lot to the experience of surfing these forums...!

ZoomZoom-RCU

.......as promised.

ZZ.

combatpigg

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Well you weren't joking about it being a great looking model..!
I've never known any sort of maple to be light wood......and you are using it for the flying surfaces..?
In the photo it looks very much like doped cloth.
I see you've got enough gas there to cross the channel, dog fight for awhile and do some sight seeing before returning to base.
How are you controlling it..?

ZoomZoom-RCU

Yeah, that was my challenge here, to make "less than light but attractive wood" flyable. The curly maple veneer is quite thin light and flexible. Forming ribs glued underneath give it its shape, as well as "steaming" it to lock in the correct curvature. I need to take some shots with a better camera to show the depth of wave in the wood. So pretty. I'd say its a tad thicker than 1/16 of an inch in thickness, and the maple will be used for all flying surfaces. Controls are just rudder and elevator due to the substantial dihedral involved, and I'm hoping due to this and the under-cambered wing it will be a pleasant flyer. That is if I can keep it light enough for a Surestart to drag around. Yeah, I might have to re-think the 2-oz fuel tank if we have a weight issue. Or even.....gasp....electrification of the power plant. Let's hope not.

ZZ.

MJD

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No-o-o-o-o-o-o on electric...

2 oz tank? CP's right about the duration. Mind you if it doesn't survive the first landing, at least you'll have 15 minutes of flight time to tell stories about. A Fuji can will give you 20 cc or so and 6+ minute flights, that's enough for me.

After laying back yesterday with headphones and watching three different years of UK BFMA free flight events on Youtube - I now think nearly anything can fly.

This should be fun - really hope it works out!

combatpigg

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All of our .061 RC combat planes used 2 oz tanks and when the tanks ran dry it didn't seem like the round of dog fighting lasted long enough. 2 oz seemed like the practical limit for tuning a .049 - .061 to burn the entire tank.

I've never used steam to form wood and have thought about giving it a try sometime.
There was an old time modeler in this area who specialized in building WWI planes of this general scale that were so realistic. I'm wondering now if he used steamed veneer for his projects.

ZoomZoom-RCU

I'm wondering now if he used steamed veneer for his projects.

Well that's entirely possible. If you used the super thin stuff you could theoretically "overaly" your pre-existing structure like a skin. I actually shopped around for slightly thicker stuff due to the monocoque load bearing structural needs of my weird concept. And really steaming is a more accurate term for what you would have to do with larger pieces of wood. With stuff in this small scale I simply dip it in boiling (or very hot water) and let it soak in till the heat and water make it supple (you can feel it get noodle like) then clamp to a form to shape and let dry. Bingo it stays that way. One item of note however is that (especially with the wings) it's good to add your poly finish (I use water based) and clamp again to keep it from warping till it dries. You can bend a bit with a heat gun after this though if you have an issue. I just used a plank with a wooden dowel the right thickness to create the undercamber and clamped the edges down till it dried. Gotta start working on the top wing soon. The biggest issue is being careful with the thin wood so it doesn't crack while cutting. I use a hand coping saw for most of the cutting out, but if splits start I revert to a rotary cutter that's like a drill bit while the piece is supported on a table edge.

ZZ.

Ps....doing the wings is the trickiest part, the fuselage was easy and the aft turtle deck I literally dipped in hot water, slowly flexed to shape, then glued in place while it was still wet and just let it dry in situ.

MJD

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I'm thinking about the 3 ounce tank I have on the .15 / Mini Contender - because I don't spend that much time at full throttle, I often land with 1.5 oz of fuel left. Mind you on the other end of the scale the Profi .061 burns through a 20cc bladder fairly quickly.

How much time do you figure you would get on an .049 on 2oz? Gotta be 12 minutes or more. I've never used a tank that large. A film can is not much more than 20cc and they run plenty long for me. Mind you, if I was having as much fun as you probably were flying combat, my perception of flight time might be a whole lot different!

MJD

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On the subject of folding materials into models, check out this laser-cut printed paper model. Similar techniques could apply..



It's been on display a while, needs some TLC and careful dusting.

ZoomZoom-RCU

Lovely albatross MJD. It's funny you should mention that because building in fanfold-foam from paper card plans is one of my main modus operandi. It's a really neat way to go, quick -tough and the sky is the limit on the shapes and details you can perform with it. I think with the rounded fuselage that would be one I would "cover" in thin veneer for the wood finish, as shaping it out of thicker stuff would be do-able, but time consuming.

Yeah I think you are looking at 10-15 minute flight times with a 2-oz and a Surestart. I would probably only fill it to 1/3 tank to start with just in case I didn't like how it behaved while testing. Lol, .....nothing like having too much fuel in a plane that's fighting you to commit suicide.

ZZ.

combatpigg

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ZZ...thanks for giving those details about how you did it..!
I picked up a pack of various diameter drum sanding ...drums and arbors from Harbor Freight. Not great quality tools to build your dining room set with but good enough for model work. The scallops on the flying surfaces could be shaped gently with this tool.
I read an article about how to build your own steamer. The key item is a sheet metal furnace duct T fitting, a pair of end caps and a pot of boiling water to deliver steam into the central entry into the T fitting. The upper chamber inside the T needs to be long enough to accommodate the entire length of wood of course.

MJD, I think the .049s could squeeze a 15 minute run with a 6x3 prop. With a AP .061 / 6x3 prop the run times were about 12 minutes. The .049s didn't deliver enough ooomph to drag their own streamer plus the opponent's streamer very well and so the .061 provided just enough extra ooomph to clear that hurdle without turning the bouts into out of control demolition derbys. AME .061s with 5x3 props were fun for the last bouts of the day if you were sad about leaving the field without suffering any total losses.
That folded paper plane is a little kewel..!

ZoomZoom-RCU

Sounds like you're on the right track CP. Cut close to your line but leave a little so you can gently "Sand to finish". I use a little dremel with a sanding drum...basically the same thing you are talking about. Your steamer is the traditional wood steamer design so that should work for you. Of course if you want simple, take some test pieces and just "dip em" in hot water and experiment with bending. It's a lot of fun and you will be surprised how good you get at it after a while. The longer it stays in the more flexible it can be, just go slow and be patient with your bending. Bend a little, dip some more, bend some more....etc. I only broke one wing panel so far, and that's because I was stupid and tried to "straighten it" a bit after it had dried. Duh!!!

ZZ.

ZoomZoom-RCU

I am now working on the fiddly-bits. Some of the most time consuming, playing with how the cowl will fit in conjunction with the struts for the top wing, and where to place the internal components in light of weight and balance. This is where things slow a bit as decisions are contemplated and finalized. Looks like the top wing will be the last thing built and installed. Sounds about right..

ZZ.

PS...any of you guys know of a creative method of fastening a cowl......without magnets, that hides the screws? I though it would be neat to not have massive screws showing on the side of the machine....but I will do what I must if I come up with nothing better.

combatpigg

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I've always wondered why a watchmaker or an orthodontist never took up scratch building model planes and gave us a better way to hold a cowl in place.

I built a cowl once where the entire perimeter edge was done "tongue and groove" style where it mates to the fuselage. All it needs is a single screw to hold the whole works to the plane.

ZoomZoom-RCU

I think your concept CP is the one I'm shooting for after looking at the peculiar cowl this thing will have. Instead of "no screws" I'm shooting for "minimal screws" for simplicities' sake. I have a design in mind and will attempt a mock up soon. It will be a two part cowl. The part aft of the firewall will be the "doesn't get opened much" design and will have the left side glued/fixed, and the right side that hinges upward like an old model T hood, fixed with 2 screws. The cowl forward of the firewall will be one-piece and come off all at once with two screws holding it. It's of the "can pop off quickly and often" type and as we are all familiar with 1/2-A engines will likely need to.

ZZ.

BMatthews

That's sure going to be a pretty looking thing. Any hint on what the final weight is going to be yet? I'm also thinking that at 24 inch span that it's going to be quite over powered with the Surestart. You may want to consider some way of choking down the power a little.

What you're going to find with the veneer is that on the wings at higher speeds the curl will want to make the wing twist. It'll tend to want to lift the trailing edge at the tips and drive the leading edge down a lot. It's not your use of the veneer, it's just what the simple sheet wood curved wings want to do. The interplane struts out near the tips will lock things together and stop that from occurring. So don't skip them.

Model railroad hobby shops are a good place to find very small screws. I've also had good luck taking apart things like old useless lap tops and cameras to find small screws that go into the plastics so they have a coarse enough thread for wood.

ZoomZoom-RCU

You are dead on target B-Matt, without the outer struts these wings would surely twist. Fortunately there are 4 struts per side, so it should be pretty stable. Yes I was hoping for a surplus of power for this design due to both the potential for a bit of excess weight from materials, as well as the draggy undercambered wings, so I hope I "guesstimated" properly. When I weighed it last on a crude scale we were around 8oz, but that was without battery, electronics, or even a top wing, so my perception is we will be pushing 12 to 14oz's when complete. Hopefully no more....but any-things possible. This is always the big I-dunno of any design as you know. I'd say 16oz. would be the outer reaches of possibility to still hope it might fly.

ZZ.

Pond Skipper

Free flight prop such as the APC 6x2 would keep the speed down.

ZoomZoom-RCU

This is true, and what I was banking on. There are always ways to bleed power, to get it however when you don't have it......not so much.

ZZ.

If it flies well enough (power to spare) I have throttles and mufflers that can always drag it back down to marginal flight thresh-holds!!!

ZoomZoom-RCU

Aft cowl being patterned after front wing strut install.....and the requisite mess of multiple projects simultaneously crowding the bench. Rudder is also being fitted.....I'm thinking of using thread hinges similar in color to the blonde wood. Cowls will be of usual soda can aluminum.




ZZ.