Anchoring the large end of a cardstock transition

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neil_w

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I have some BT50 -> BT55 transitions to make, somewhere around 1-2" long. They will be slid over the BT50 and butted up against the end of the BT55. Do I need to do anything to the BT55 end to support it and keep it round? I had wanted my 5055 centering rings to extend slightly beyond the end of the BT to provide an anchoring point for the transitions, but that's not gonna work out. Alternately I could cut my own centering ring to insert in the end of the transition, but cutting a precise 5055 ring is going to be a pain.

Will it work OK to just glue the transition to the end of the BT? If not, is there a better way to do it that doesn't require a centering ring?
 

Micromeister

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Generally I like to form an internal cardstock 1/8" to 3/16" high stop from the same cardstock as the shroud. I lay a light line of White Glue to the perimeter of the shoulder and around the upper end of the smaller tube. Slide the Cardstock shroud down into the glue.
 

rstaff3

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I like making the large end a skosh too big and let the bigger tube force the shroud round. Put a glue bead on the large end and let it dry. Then sand the shroud flush with the tube.
 

neil_w

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Generally I like to form an internal cardstock 1/8" to 3/16" high stop from the same cardstock as the shroud. I lay a light line of White Glue to the perimeter of the shoulder and around the upper end of the smaller tube. Slide the Cardstock shroud down into the glue.
Can you clarify just a bit? I'm not quite getting the picture.
 

rstaff3

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I think he means that you cut a ring from cardstock whose od is a tad smaller than the diameter of the larger tube. When inserted into the shroud, it will support the cardstock and will keep the base circular.
 

Gary Byrum

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Neil, I do a lot of shrouds. Usually I find that the CR that is in the shroud is a little recessed and the edge of the shroud is all there is to glue to the tube. That doesn't feel or even look secure to me. I find I'm usually sacrificing an additional CR to fit flush with the end of the tube, and I use my OLFA circle cutter to cut another one to laminate the one in the shroud. The end result is a shroud with a flush end that I can glue to the other CR in the tube. I know it sounds like a lot of CR going on, but you don't have to be all that precise with the "laminating" CR. You just have to make sure it gets flush with the end of the shroud. If your stock is a little too thick, peel or sand some of it off. If it's too thin, add a little more. Best to find some stock that will fit good the first time. I do it all the time.
 

Micromeister

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Can you clarify just a bit? I'm not quite getting the picture.

sorry I don't have a photo of the process but it's really not that involved. form an INTERIOR cardstock ring that fits the forward end of the Large Diameter body tube.
glue in place with 1/8" to 3/16" projecting above the body tube. When dry slide the cardstock shroud over the smaller diameter tube with a light line of white glue around the area where the shroud will seat on the forward end of the small tube and around the Large Dia body tube 1/8" shoulder. You'll have to adjust the interior shoulder by test fitting before glueing in place to ensure the should seats correctly with the internal 1/8" shoulder seated squarely against the interior of the shroud.
 

neil_w

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sorry I don't have a photo of the process but it's really not that involved. form an INTERIOR cardstock ring that fits the forward end of the Large Diameter body tube.
glue in place with 1/8" to 3/16" projecting above the body tube. When dry slide the cardstock shroud over the smaller diameter tube with a light line of white glue around the area where the shroud will seat on the forward end of the small tube and around the Large Dia body tube 1/8" shoulder. You'll have to adjust the interior shoulder by test fitting before glueing in place to ensure the should seats correctly with the internal 1/8" shoulder seated squarely against the interior of the shroud.
Do you mean this?


If so, it seems like you're almost making a coupler out of the cardstock. That seems reasonable, although I won't be able to do it at one end because there will be a centering ring *almost* right up against the end of the BT.

It's conceivable I could have my 1/8" light ply centering rings extend a bit beyond each end of the BT and provide an anchor for the shrouds, but it would require some really precise building, and it would preclude my filleting one side of the centering rings. On the other hand, I'll have some TTW fins also holding the two tubes together, so maybe centering ring bond strength isn't quite as critical.

Gary Byrum said:
I find I'm usually sacrificing an additional CR to fit flush with the end of the tube, and I use my OLFA circle cutter to cut another one to laminate the one in the shroud. The end result is a shroud with a flush end that I can glue to the other CR in the tube. I know it sounds like a lot of CR going on, but you don't have to be all that precise with the "laminating" CR. You just have to make sure it gets flush with the end of the shroud. If your stock is a little too thick, peel or sand some of it off. If it's too thin, add a little more. Best to find some stock that will fit good the first time. I do it all the time


I'll have to experiment a bit and see what it's like trying to cut those pieces. 5055 rings are very skinny and I suspect will be hard to work with. I also don't have a circle cutter at the moment....


shroud.png
 

kjohnson

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Why not have the centering ring you're talking about being close to the end of the tube actually poke out of the tube a smidge. That gets you a place to glue the transition to, without needing to add a new part? I do that sometimes for boat tails.

kj
 

neil_w

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Why not have the centering ring you're talking about being close to the end of the tube actually poke out of the tube a smidge. That gets you a place to glue the transition to, without needing to add a new part? I do that sometimes for boat tails.
I still could do that. My reasoning against it (which is very tentative I admit) was that (a) I'd get slightly less secure mounting of the centering rings, with only a "natural" (e.g., whatever gets squeezed out) fillet on the inside (under the tube) and none on the outside, and (b) in order to achieve that level of placement precision it means I'd need to glue the rings to the outer tube first, and then that means I can only get fillets on one side of the rings on the small tube as well. The centering rings are a bit loose on the inner tube, so I was hoping to glue them securely as possible.

Conceivably I could let the rear ring stick out and anchor the transition, and inset the front one and do it some other way. That would enable me to glue the rings first to the inner tube, and slide it into position as needed. That may be the best compromise approach.

It is very hard to convey what I'm saying here, sorry if it's not coming through.
 

Gary Byrum

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I still could do that. My reasoning against it (which is very tentative I admit) was that (a) I'd get slightly less secure mounting of the centering rings, with only a "natural" (e.g., whatever gets squeezed out) fillet on the inside (under the tube) and none on the outside, and (b) in order to achieve that level of placement precision it means I'd need to glue the rings to the outer tube first, and then that means I can only get fillets on one side of the rings on the small tube as well. The centering rings are a bit loose on the inner tube, so I was hoping to glue them securely as possible.

Conceivably I could let the rear ring stick out and anchor the transition, and inset the front one and do it some other way. That would enable me to glue the rings first to the inner tube, and slide it into position as needed. That may be the best compromise approach.

It is very hard to convey what I'm saying here, sorry if it's not coming through.
You could always use a coupler in the tube, let it stick out...eh...a 16th / 32nd of an inch? Unless you really needed that CR for a tube to stick through. OR....Cut off a portion of a coupler and glue the CR to it. And glue that inside?
 

kjohnson

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From the sounds of the tubes you're using (bt-50/bt-55) you probably won't be using super high thrust motors. Most likely you won't have trouble with the CR letting go if you don't have a fillet on each side. You can still glue the CR
's to the inner tube and then slide the whole thing into the outer tube, heck- you could even not glue the transition-anchor CR to the inner tube, but just have it slid into place as you glue in the other end, then pull off the CR and put in your fillet, then glue on the CR.

kj
 

neil_w

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You could always use a coupler in the tube, let it stick out...eh...a 16th / 32nd of an inch? Unless you really needed that CR for a tube to stick through. OR....Cut off a portion of a coupler and glue the CR to it. And glue that inside?
If I had any BT55 coupler stock on hand I'd use it in a heartbeat (as I would any cardstock centering rings), but I don't. My parts stock is not significantly larger than what I have specifically ordered for the build(s) at hand. Unfortunately I didn't think of ordering either of those on my last BMS order. :(

From the sounds of the tubes you're using (bt-50/bt-55) you probably won't be using super high thrust motors. Most likely you won't have trouble with the CR letting go if you don't have a fillet on each side. You can still glue the CR
's to the inner tube and then slide the whole thing into the outer tube, heck- you could even not glue the transition-anchor CR to the inner tube, but just have it slid into place as you glue in the other end, then pull off the CR and put in your fillet, then glue on the CR.
I think you're right that I don't really need to worry so much about the extra strength. I'll still do what I can though just for piece of mind.

I think I know what I want to do, will experiment and see how it goes. My progress (should anyone care) will be documented in the Starship Avalon build thread.
 

rocketguy101

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If I had any BT55 coupler stock on hand I'd use it in a heartbeat (as I would any cardstock centering rings), but I don't. My parts stock is not significantly larger than what I have specifically ordered for the build(s) at hand. Unfortunately I didn't think of ordering either of those on my last BMS order. :(
you can make your own tube couplers from body tubing
[video=youtube;iH3HesegWv0]https://www.youtube.com/watch?v=iH3HesegWv0"]https://www.youtube.com/watch?v=iH3HesegWv0[/video]

also you can make your own centering rings from cardboard and a circle cutter such as an Olfa or X-acto (found the latter in the craft section at Wal Mart)
 

Micromeister

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Why not have the centering ring you're talking about being close to the end of the tube actually poke out of the tube a smidge. That gets you a place to glue the transition to, without needing to add a new part? I do that sometimes for boat tails.

kj
Absolutely Kevin!
If you have a centering ring needed anyway then using it as the seating shoulder is just fine.
 
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