BT-101 centering rings?

[Rick Lindsey]

Does anyone offer "stock" centering rings that fit in a BT-101? I'm looking for fibre/paper/cardboard rings that fit either a 29mm motor mount or some sort of happy cluster into a BT-101 tube. I'm hoping to avoid paying for custom work, though I'm tempted to invest in a circle cutter and some matboard and just do it myself.

thanks,
Rick

 

[mwiggins367]

The BT 101 from www.semroc.com has an inside diameter of
3.896". They might have a centering ring for the BT101.

www.jonrocket.com sells motor mounts for a 3.9" body tube.
https://www.jonrocket.com/bodytubes.html

I think that the motor mount is made by Sunward.

https://www.sunward1.com/mounting29.htm

Contact Sunward or Jonrocket (or Semroc). They should be able to help you.

 

[maricopasem]

If you're willing to make your own, here's how I've done it. I create a template in MS Word or PowerPoint (see attached, not-to-scale, thrown-together-in-30-seconds example). I use a glue stick to attach it to the cardboard (of varying thicknesses depending on the project). I can then use scissors for the outside and an exacto knife for the inner rings. They come out great.

 

[Rick Lindsey]

I just remembered that I had a program that prints motor mount templates. I just printed one up, but I'll have to wait until my totally tubular order arrives to see if it's accurate (i've had issues with VCT's miter cut templates being the right size, but I'm not sure if that's because VCT is assuming I'm printing on cardstock (I'm not) or if it's just a problem with scaling and my printer) . Thanks!

-Rick

 

[Rick Lindsey]

Has anyone ever tried a paper or cardstock laminated balsa centering ring? I can see why you wouldn't use just a plain balsa ring (breaks too easily along the grain) but it seems that a paper or cardstock laminated balsa centering ring might be quite strong, yet still quite light.

I'm a little worried about cardboard CR's on a 29mm mount, but I really don't want the weight of plywood centering rings in this rocket.

thanks,
Rick

 

[ben]

Originally posted by Rick Lindsey
Has anyone ever tried a paper or cardstock laminated balsa centering ring? I can see why you wouldn't use just a plain balsa ring (breaks too easily along the grain) but it seems that a paper or cardstock laminated balsa centering ring might be quite strong, yet still quite light.

I'm a little worried about cardboard CR's on a 29mm mount, but I really don't want the weight of plywood centering rings in this rocket.

thanks,
Rick

you have a PM

thanx, Ben

 

[Micromeister]

Rick:
I usually just cut my own out of cardstock or liteply. I was explaining in another thread that keeping the model light you can use just about anything you want for centering rings. example was a BT-101 5 D12 clustered 3X upscale Goblin which as 14ply shocard rings.
I haven't laminated balsa with paper but I sure have laminated 3 layers of light cardstock to make a heavier centering ring.

If your going with a 29mm motor mount you may as well go with plywood centering rings as your gonna be putting AP motors in it.

 

[RoyGreen]

Originally posted by Rick Lindsey
Has anyone ever tried a paper or cardstock laminated balsa centering ring? I can see why you wouldn't use just a plain balsa ring (breaks too easily along the grain) but it seems that a paper or cardstock laminated balsa centering ring might be quite strong, yet still quite light.

I'm a little worried about cardboard CR's on a 29mm mount, but I really don't want the weight of plywood centering rings in this rocket.

thanks,
Rick

Cardboard rings can work very well with high thrust motors if triangular trusses are used to transmit stresses longitudinally along the tubes. This is the method Apogee uses in their 1/70 Saturn V to keep its weight down so a single G80 can lift it.

 

[Rick Lindsey]

I'm definately planning to put AP motors in it, but the target motors are of the low thrust, long burn variety. I'd really love to be able to loft it on an Apogee F10, but I suspect that's a pipe dream. I definately don't want to jeopardize it's chances on a G20 (though I suspect a G20 would be fine even with plywood centering rings, but why chance it?).

This is for a model of a phoenix missile, which typcally seems to need noseweight for stability, so I'm trying to be extra-careful about weight added to the aft end, as I may have to counteract that with nose weight, effectively doubling the weight penalty of the plywood.

I have no plans to ever fly this on a G80. If G20's become unavailable or prohibitively expensive, I'll probably try to fly it on 29/40-120 blackjack reloads (where's my 62g blackjack reload? *grumbles something about 63grams of propellant*).

Out of curiosity, what is shocard?

thanks,
Rick

 

[TeenRocketNerd]

what about laminating 2 or more layers of thin balsa together, with the grain running perpendicular to the piece below it, making a sort of balsa-ply?

Also, you could run full length balsa spars to between the centering rings, kind of like what someone said earlier.. Here's a rough idea of what I mean; this idea came from "Model Rocket Design and Construction."

 

[Micromeister]

ShoCard and a Outdoor board which is weather resistant are signpainter/signmaking materials.
14 ply laminated cardboard about .048" in thickness, much heavier then composition board in 28" x 44" sheet size for about 3 bucks.