Allthread - where did it start?

[jetra2]

I am curious to know where the technique of using allthread to supposedly strengthen a fin-can section started.

I've heard that it provides structural integrity to the rocket if it is done right and in the correct rocket, but if it's not used right, or in the right rocket, it will just add a lot of unnecessary weight.

Reason I ask is because I am considering using it on my 8" QuikTube rocket, and I want to know if it'll be helpful at all.

Thanx,
Jason

 

[DPatell]

I have no idea where it started, but the theory is this:

The motor bears on the aft of the motor tube, which is nearest to the rear CR. The rear CR takes a large portion of the load. Allthread is used to tie all of the CR's together. Therefore, instead of the aft centering ring taking the brunt of the force, it equally displaces it along all of the CR's.

In most cases it is just dead weight, not really helping at all.

The same thing can be done using wooden dowel. As it is strong axially, the dowel makes a good, lightweight alternative if you feel the need to tie all of the CR's together.

 

[Stymye]

I've always wondered about this

I see it working with metal centering rings..
otherwise the result is still no more stronger than the centering rings themselves (now with extra holes thru them)
seems like the motor mount tube and/or body tube interconnect the rings anyway...perhaps there is a better reason?

 

[Johnnie]

The effect also works in reverse...My all-thread goes all the way to the top bulkhead, so the motor will push and spread the force out across the centering rings. But ejection will spread the forces in reverse down the centering rings for recovery. In my theory (mind) I am minimizing the stress on the cardboard tubing we use for HPR.

 

[cls]

In my theory (mind) I am minimizing the stress on the cardboard tubing we use for HPR.

let's take that idea to the next level ... how about a rocket with a sturdy internal structure and something very thin for the skin? maybe paper or fabric or a couple thin fiberglass layers ...

 

[Smokin' Rockets]

Originally posted by jetra2
I am curious to know where the technique of using allthread to supposedly strengthen a fin-can section started.

**I would say it started in large heavy high thrust L3 type rockets. It was primarily used to spread the load throughout the centerings. If a fincan is constructed properly, with good quality epoxy and parts, all thread is overkill. Once a fincan is finished and glued in the airframe, technically the middle center rings can be removed. They are not taking up any thrust, and just centering the motor tube. The fin joint to the airframe in the slots if doing that and spreading the load. The rear ring is used for mainly motor retention. The foward ring for shock cord mount.

**Now I'm not saying to remove your center rings, but you could. Now you could attatch your shock cord anchor poing to the allthred to spread the load away from the top center ring alone. But once again if proper materials and gluing techniques are used it should not be neccesary. We now have so many alternatives to reinforce with fiberglass, kevlar, carbon fiber, etc.

I've heard that it provides structural integrity to the rocket if it is done right and in the correct rocket, but if it's not used right, or in the right rocket, it will just add a lot of unnecessary weight.

**Yes it will provide extra strength and structural integrity but in most cases it simply is not needed.

Reason I ask is because I am considering using it on my 8" QuikTube rocket, and I want to know if it'll be helpful at all.

Thanx,
Jason

The more you reinforce a rocket by adding unnecceasry weight, the more forces on the entire rocket. Especially during recovery. I see too many overweight pigs that dont perform very well.

The bigger they are....the harder they crash.