Build Thread - Another J-Dub in the workshop

[thevon]

I've only used carbon on the Reaper and Bat. Sean and Ezza would know what's best in wood. Basswood is often mentioned.

[sean]

Spruce is good - 3mm works well. I like wood on the TE because it's easy to work with and cheap, but obviously not as stiff as carbon.

[sf2]

All the steve drake foamies I've flown have this drag spar, and I've put it on my own models, It's normally a piece of 1/4by1/4 spruce the length of the wing(obviously).Hinge then works at you own purchase of some hinge or a bevell and some tape/etc.
The most recent tecnique I've seen is to fully attach the aileron to the wing,mark off a 1/4 or so line and cut it off.
I've used goop and epoxy to join them on , with the covering wrapped around they're never coming off.Just gives a nice straight edge to attach the aileron and some degree of reducing twist and flex on the T.E.
Like Seans Idea of the carbon aileron, thats for my next foamie(in a box in the garage)
Don't know where you live but the RCware house in logan sells Aileron/TE material.

[drcuzo]

I have ordered some 6mm carbon spars and spruce from frontline hobbies and have scored some TE. I think I will laminate the spruce to some CF strip. I just can't help myself, I love to overbuild things. It will probably be crash proof because it will not get high enough to do any damage.

Steve

[sf2]

wow,not going to be any flex there, how you going to join the carbon strip 1) to the foam 2) to the spruce? I've got a project to convert a 41 in balsa plane to foam and was thinking of using carbon strip on top and bottom plus a TE tecnique you describe above. Let Me know what glue(s) you use and how it goes.
DH

[skyboyken]

Hi Steve,

great to meet you today!

Please keep your JW as light as possible behind the CG. Up front is where it needs the strength, the durability and the weight. All the TE needs is to be straight and stiff enough to mount the elevon. A nice piece of spruce is perfect, and is all you'll ever need. A piece of carbon tow (I have plenty if you need some) across the TE join is enough strengthening.

A few true truisms: All EPP planes are durable. Lighter planes fly better than heavier ones. You can always add ballast to a light plane, but you can't take weight out of a heavy one. Queensland is not America; our winds are usually light.

Go Great!

Ken.

[drcuzo]

Raptor almost done so the JW is back on the radar. Any opinions on gluing the spars in?

Steve

[thevon]

Steve, I'm not sure about specifics of the JW but PU glue is pretty much the norm for gluing main spars in. If you haven't used it before, make sure you get a few tips - it's funny stuff. But really excellent for gluing spars. Is there a pre-cut tunnel? Or do you put it in a trench??
A

[drcuzo]

Andrew
It has a precut trench. I have some gorrilla glue. Is it flexible enough?
Steve

[felix]

another alternative that works quite well is shoe goo or a glue called e6000.both rubbery for some compliance and bond well

[sean]

PU would be my pick - it expands into all the holes in the EPP and forms a really strong bond, fills the trench, and is also flexible. It's tricky to use, you have to sit the wing in the beds and weight the spar down with as much weight as you can find, otherwise the glue expands so much it'll lift the spar out and possibly bend the wing around the spar cutout. It expands to probably more than 10 times its original volume.

One technique I use now is to pour some PU into a plastic cup then mix one or two drops of water (no more) into it. It will start to foam within a couple of minutes and change colour to an opaque yellow. Let it foam a bit more, give it another thorough mix and then use a spatula or ice cream stick to cover your spar in the foamed PU before placing it in the wing, then weight it all down in the beds. Doing this reduces the chance of the foam expanding too much, and helps the glue expand evenly rather than create lots of big bubbles.

Shoe Goo would give good results too, but you'd have to use a lot to get a good bond in the square trench, and that would cost a bit.

[felix]

great tips there sean and sounds like the way to do it for sure, will give it a go on the eagle ;D. i had some PU here but i wimped out on using it on the bee and went the easier route with shoe goo.i got my PU given to me by mark so can't compare the costs.shoe is $10/tube and the bee took 3/4's of a tube with very liberal use.

[sean]

Hey Felix, I don't blame you for not using PU on the Bee, with no beds it's a bit riskier. A bottle of PU isn't cheap but you use very little, I have a bottle I bought two years ago and have only used about a third of it. So it's very cheap in the long run.

[felix]

Is that all you use!!!?

Glad I read that before I use it! The way I use glues (my first silicone non moving hinges being a good example lol) I would be carving a wing out of a great ball of PU foam!.....or i can picture myself with a cup of PU madly foaming out the top lol

[sean]

He he, you have to be pretty sparing with it or it'll foam everywhere and is a %$#@ to get off whatever it dries on once that happens. Eg If you only fill the first 5mm or so of the cup then mix in a drop or two of water it'll foam out the top of the cup!!! But most of that is air bubbles, so when you stir it after it's expanded it'll go down to a smaller volume again. That's why I like foaming it before application, you get less air bubbles and a more even bond (plus it'll set faster).

The other reason I still have so much left is because I have a pretty big bottle of PU!