Foam BD alternative spar system

[Cuddles]

I want to scratchbuild a foam Bubble Dancer but i'd like to use it just with a light histarter and /or handlaunching it, like a sort of unlimited HLG.
For those reasons as well as for an easier build, i would borrow an alternate spar siystem from the DLG realm.
I could use a disser skin, some pultruded carbon rods or a carbon D-box, but i'd like to have your opinion.

Best regards,

Francesco

[kak8]

You need some kind of a spar - just to make the wing joiner area strong enough.
Foam is rather soft.
Maybe some 10 - 15mm carbon tubes, just under the upper skin - like Phil Barnes in "vaccum bagging made easy".

But a spar from top to the buttom of a D box is best.

Adam

[Cuddles]

Well, i was thinking to avoid two wing joints and have just one in the center,with a straight tube, like a Thermal Dancer:
http://www.rcgroups.com/forums/attachment.php?attachmentid=1674717
I like this pod too!

Francesco

[Double Pappa]

with the guide lines you have given I really don't see any problem with your plan. I would use a plywood plate on each wing root to join them together. Make sure your plywood piece matches the airfoil perfectly and them epoxy it in place. Drill through it and the foam to insert your joiner tubes. Put something in the joiner tubes to keep the epoxy out of them. An aluminum tube like an old arrow shaft makes a great drill for this purpose. Make sure your top and bottom rods firmly seat into/on the plywood "rib".

[Cuddles]

I've read somewere that the joiner tube should actually touch both the upper and the lower skins to be effective, is that correct?

This thread supposed to be a poll between disser, XPseries and pultruded carbon a la Taboo GT but i failed to put on the poll :o

Also i would avoid kevlar in large quantity (i.e. skins) but i have some 200g/mq carbon fabric that i plan to use for pod.

Francesco

[Double Pappa]

In my mind it would be more important that the joiner tube is connected to the tubes you are running on the top and bottom. If they are joined by epoxy and micro ballons you should have a very sturdy wing.

PP

[Cuddles]

the tubes you are running on the top and bottom

So your vote is for pultruded carbon rods?
I've drawn a crude sketch, i'm understanding correctly your opinion?

[Double Pappa]

yah, I don't see wht that wouldn't work perfectly. The stress of the joiner will be transmitted to the pultruded tubes you have running just under the skin. You could probably run a top and bottom tube full length and then run a second one out to the first wing break. That system should flex very smoothly and make for a very nice flying airplane.