I can't figure out how to build this

[neil_w]

Thank you again to everyone who gave their idea, it definitely helped clarify my thinking.

What I have decided is to cut the ring into two pieces, a bottom piece and a top piece. There are two reasons which ultimately overrode all other considerations:

• Ability to glue the rings at the very end, after construction and painting are (mostly) finished.
• Ability to adjust the pieces to fit if the rest of the construction isn't perfectly aligned

It won't be trivial to build it this way either, but I believe it eliminates the worst of the problems with the other approaches.

I am going to half-slot the top fin and the top half-ring. That'll give that ring piece (which is somewhat more than half of the ring a good solid anchor point, without needing to do a two-piece fin.

There are still lots of details to be worked out, but having made this one decision will help things move along now. My next big decision will be which fins (if any) to slot into the body tubes, and whether to spring for laser cutting, which will help achieve the necessary precision for the whole assembly. The BT5 pod tubes, in particular, won't have any inner tubes, so slotting there would mainly be for alignment purposes, not strength. Slotting the main BT for the pod support pieces could be beneficial. I'm having a crazy thought about this, might post here later for feedback (need to convince myself it's not totally nuts first).

Anyway, onward. I guess I better get back to finishing up the rest of the design details....

 

[jqavins]

Some thoughts from this row of the peanut gallery. Since I'm coming in late, please forgive me if some of this has been covered. Sorry I didn't see this thread when it started.

Half-slot interlocking joints: precision in the radial positions of the slots along the ring is critical, as you said. But the depth of the slot isn't really all that important. Obviously there is a minimum depth, but if it's a little deeper, so that the two pieces don't bottom out on each other when the edges are in position, the small gap that results will be covered over by the fillet, and doesn't really matter.

Painting the interior of the ring after assembly:


For the aft ends of the side tube if they've been slotted all the way back: I like Big Mac Daddy's idea of capping them off with tail cones or faux nozzles designwise, but structurally it's really only the shoulder of such a thing that you'd need. Just inserting a quarter inch long bit of coupler would do the trick to restore and reinforce the roundness of the end.

While that is going on, make the equivalents of long BT-5 couplers the length of your outboard pods. Basically take a BT-5, cut a longitudiinal lengthwise slot, and use masking tape or other rough surface tape to hold the edges together so it just slides inside an intact BT-5.

BMS sells coupler stock in 34 inch lengths. Four bucks.

[If] your wing slots are off by more than YOU can tolerate you can widen them to fit (whichever way you widen them, the ring SHOULD be in direct contact with either the inside or the outside of the slots, and you can use the cheaters to fill in the difference.

Or not the cheaters. This single bit could be used no matter what other method you're using that has the ring passing through a slot. That is, you can make the slot a little over wide then fill the gap with - well - something. Then paper over the filler, bridging from sound wood to sound ring, and burry the paper in the fillet.

In general, I think you might be best off resigning yourself to a heavy build. Go with thick walled tube for the ring so it stays round. Reinforce joints where needed in the ways many have noted above or in other ways. Add the nose weight you need and launch on D or E engines (or even F engines if you have to, but you probably won't). Relax and let it be heavy.

 

[BABAR]

BMS sells coupler stock in 34 inch lengths. Four bucks.

Wow, Bob’s your Uncle!

Cut the full wing plane-form INCLUDING the silhouette of the pod tubes. Make the pod silhouette a bit wide, we’ll sand it down later .It will be stronger as a single piece and we are gonna beef it up more. Slot it for the ring.

Mount both wings, rudder, and then the ring. I think it will be easier to fudge with just rudder and wing slots the mixed balsa slots and ring slots, bit either will work.

Cut the couplers to length of the pods

Cut in 1/2 lengthwise and then take a long strip off each edge that accounts for the wing thickness.

Mount one on top and one on bottom. Each will have ONE slot on the rear end for the ring. You can probably eyeball this.

Now cut the BT-5s in half lengthwise, again shave off the edge to account for wing thickness, then mount one on top, one on bottom, eyeball the slot for the ring.

Once dry, sand the “extra” wide tube silhouettes down even with the tubes.

 

[Daddyisabar]

What would you do if I build out of turn, would you stand up and walk out on me?

Lend me your ears and I'll give you a plan, yes I'm certain that it happens all time.

I get by with a little help from my friends, oh I mindsim with a little help from my friends.