Balsa for centerging rings

[reduc]

Can we use balsa to make centering rings for model rockets?

Remi.

 

[rocketkyle]

yes, as long as you "pot" the back end of each cr with epoxy. This way, the balsa acts as a guide, and the epoxy is the actual cr. Good luck!

 

[dr wogz]

Salut Remi! Est-ce qu'on passe un bonne été? Un peux trop chaude?

Ideally, I would vote no.
But this is my opinion, and others can and will differ!

I find balsa a little too brittle for a CR, as the forces exerted on it to get it in place would surely crack it. The grain is the problem.. It's also somewhat flexible, so you can glue in a warp. Also, it sands too easily, which can offset the center hole (concentricity)

Of course, I'm thinking of a 1/8" thick piece, medium soft. You can get 'hard' balsa, which might make it more durable. You might also soak it in CA to stiffen it up..

Most (lpr) seem to have this 'fiber based' material, akin to paper, or actual thick card stock. This is duarable, and is not prone to 'having a grain' to crack along.

 

[GL-P]

I can't speak either way but you can use end grain balsa where the grain runs like the layers in plywood. It's hard to find. You could double layer the balsa though and run the grains in different direction (sp?)

 

[polaris]

I think the big thing with centering rings is they have to be stiff. I believe some people have used paper, foam-core board and picture matting, as well as plywood and G-10 fiberglass.

Like Kyle says, you are better off doing something to stiffen it. Then again, you might use the materials others have already proven.

 

[wwattles]

If you are in a situation where you are required to use balsa, then yes, it can be done. An unconventional, but effective, way to do it would be to make a web. Basically, you put 3 or 4 strips of balsa running the length of the motor mount tube that extend out like fins inside the rocket to the inside of the body tube. Put one balsa centering ring on the front end of that, and it'll hold the ejection charge pressure inside, and the web behind it will keep it strong enough.

WW

 

[Stones]

...use basswood. Only slightly heavier, with a tighter grain for strength.

 

[Rocketmaniac]

My opinion is that if you just HAD to use balsa for centering rings, you should at least put a good coat/layer of epoxy to add strength.

With that said, I think basswood would be a much better choice.

 

[Stymye]

I stay away from single grain materials for rings.. like balsa , basswood .. some basswood I've used in the past will snap quite easily along the grain.. I would rather use paper, foamboard,
plywood from any material including balsa and bass is good... but not a thin single grain material, wrong application for that.

 

[Rocketmaniac]

Originally posted by stymye
plywood from any material including balsa and bass is good... but not a thin single grain material, wrong application for that.

You're right. I was thinking plywood, but only wrote basswood...

 

[Stymye]

Randy , I was just making a general(opinion) post to the thread , not specifically your reply.

my apology for not being more clear about that.

 

[mike_bar]

Originally posted by stymye
Randy , I was just making a general(opinion) post to the thread , not specifically your reply.

I like all the general opinions here. It is interesting to read the various comments, and there are so many good ideas and great knowledge at TRF.

Remi (Reduc) did not mention whether the question is regarding low, mid, or high-powered rockets. There are lots of good replies here which can apply to different power requirements.

I have made centering rings from cardstock or 5-ply rings (two layers of balsa sandwiched between bond paper). The balsa is layered with grain running 90-degrees apart. These rings are strong and light but time consuming to build. The basswood or plywood is strong, but I like the light-weight construction for myself.

My perspective is focused to low and mid-powered rockets. I also like to use light-weight construction techniques. I have found many good tips at Apogee's Model Rocketry E-Zine.

Specifically, a good read is Apogee's Model Rocketry E-Zine, "Paper Centering Rings for HPR".

I will have to buy Tim Van Milligan’s book, “Model Rocket Design & Construction.”

Regards,
Mike

PS- Man, this sounds like an advertisement. Sorry for that. I like Tim’s ideas.

 

[Stymye]

I will have to buy Tim Van Milligan’s book, “Model Rocket Design & Construction.”

You won't be dissapointed! Well worth the price

 

[Rocketmaniac]

Originally posted by stymye
Randy , I was just making a general(opinion) post to the thread , not specifically your reply.

my apology for not being more clear about that.

You said something that was important and that I actually thought about but did not write in my reply. It was one of those brain fart things.... I was meaning to say it, but didn't..... You were just keeping me straight. (Lately, I need that more and more)

 

[Loon]

Multi layer cardstock is stronger than balsa and easier to make
Being somewhat cheap, I use some thick cardstock scrap sandwiched inbetween two #110 cardstock. This produces centering rings that are very stiff.
You might try balsa sandwiched between cardstock, cardstock reinforced balsa fins are much stronger. Sealing the edges with CA could also help.
Tip; paper and cardstock also have a grain to them, orientate the layers 90 deg to eachother.

 

[DynaSoar]

Originally posted by Reduc
Can we use balsa to make centering rings for model rockets?

Remi.

I've done it many times, usually when I was in a hurry and didn't have something else better to use, but sometimes just to do it.

Either:

make two rings for each centering ring and glue them together with their grains perpendicular, to form a 2-ply so the force doesn't crack it, or

cut the balsa ring, then cut two cardboard rings out of a ceral box or similar, and glue one to each side.

Either way, make it a little large on the outside and a little small on the inside, and sand it to a good fit.

Sure, basswood is better, and ply better yet. But good enough still works.

 

[reduc]

Thank you very much. I appreciated your replies.

Mike_Bar, in my question, I've specified centering rings for model rockets. For me, it meant low power (A-D). But from reading the replies, I realized that it wasn't specific enough. Sorry for that.

Dr Wogz, j'ai passé de très belles vacances, à mon chalet, sur le bord du fleuve À date, je trouve que nous avons un très bel été

Thanks again everybody for your kind replies.

Remi.

 

[mike_bar]

Originally posted by Reduc
Mike_Bar, in my question, I've specified centering rings for model rockets. For me, it meant low power (A-D). But from reading the replies, I realized that it wasn't specific enough. Sorry for that.

My bad... I will read more closely...
I agree 100-percent! model rocket generally mean LPR.
Great ideas here too.

 

[polaris]

Sticking only with LPR, and light weight, I really like fiber rings. Because of the paper structure, they appear to have good stiffness in all dimensions. They glue well. They seem to have a high strength to weight ratio.

You can get them from BMS. The material is available at Michaels as picture matting.
It cuts well by hand. If you have access to a laser, custom cutting intricate shapes is very easy.

 

[hokkyokusei]

I've used balsa centering rings on light model rockets.

If you need additional strength, use two rings back to back with the grain at right angles. Using this method you can get away with using very thin balsa.

 

[brockrwood]

I like all the general opinions here. It is interesting to read the various comments, and there are so many good ideas and great knowledge at TRF.

Remi (Reduc) did not mention whether the question is regarding low, mid, or high-powered rockets. There are lots of good replies here which can apply to different power requirements.

I have made centering rings from cardstock or 5-ply rings (two layers of balsa sandwiched between bond paper). The balsa is layered with grain running 90-degrees apart. These rings are strong and light but time consuming to build. The basswood or plywood is strong, but I like the light-weight construction for myself.

My perspective is focused to low and mid-powered rockets. I also like to use light-weight construction techniques. I have found many good tips at Apogee's Model Rocketry E-Zine.

Specifically, a good read is Apogee's Model Rocketry E-Zine, "Paper Centering Rings for HPR".

I will have to buy Tim Van Milligans book, Model Rocket Design & Construction.

Regards,
Mike

PS- Man, this sounds like an advertisement. Sorry for that. I like Tims ideas.

This is a great idea. It seems to me that it ought to be possible to make "balsa plywood" by simply gluing two thin sheets of balsa together but making sure that grain of sheet 1 runs perpendicular to the grain of sheet 2. That would make a really strong, but light, balsa material for centering rings and bulkheads, and the like, would it not? I am going to try it if I can ever find time for my hobbies. If it is successful (or not), I will let everyone know.

 

[Funkworks]

I love it when someone brings back a 16 year yo thread! Nothing comes closer to a real time machine!

As for custom balsa plywood, @BABAR recently made fins out of it here.

 

[neil_w]

This is a great idea. It seems to me that it ought to be possible to make "balsa plywood" by simply gluing two thin sheets of balsa together but making sure that grain of sheet 1 runs perpendicular to the grain of sheet 2. That would make a really strong, but light, balsa material for centering rings and bulkheads, and the like, would it not? I am going to try it if I can ever find time for my hobbies. If it is successful (or not), I will let everyone know.

Two-layer balsa laminates are not as strong as you might think, although they are undoubtedly fine in many situations.

 

[BABAR]

I love it when someone brings back a 16 year yo thread! Nothing comes closer to a real time machine!

As for custom balsa plywood, @BABAR recently made fins out of it here.

I like it when I have structures that I know are going to get stressed in two different directions, example is rotor stops for helicopter and air brake rockets.

for easiest use, you need to cut the pieces separately if your are using a knife. It’s a bear to cut once it has been glued. You also need to stick it in parchment or wax paper and then a book or something, (some people iron it), otherwise it warps like crazy with wood glue.

 

[Ez2cDave]

Can we use balsa to make centering rings for model rockets?

Yes, we can . . . Fins, too !

I like to make "balsa plywood" ( layers of 1/32" balsa ) . . . Alternate the grain direction for maximum strength and stiffness !

For thicker pieces, I alternate the Grain BOTH 45 degrees and 90 degrees . . . VERY strong !

Dave F.

 

[DaHabes]

Two-layer balsa laminates are not as strong as you might think, although they are undoubtedly fine in many situations.

Add a layer of copy paper or, better yet, cardstock in between the balsa layers, then seal the outsides of the balsa with diluted Elmer's white glue. Should handle any LPR you throw at it.

 

[Ez2cDave]

Add a layer of copy paper or, better yet, cardstock in between the balsa layers, then seal the outsides of the balsa with diluted Elmer's white glue. Should handle any LPR you throw at it.

A mental image of using a Manila file folder just popped into my head, too. However, my choice of adhesive would be Elmer's Carpenter's Wood Glue ( waterproof ) or similar, pressed down hard, until fully cured.

Dave F.

 

[jqavins]

I've done things like this (I don't remember whether centering rings, a bulkhead, or some other application) and found the only issue to be getting the thing into position. Once there and glued in solidly, single layer 1/8" balsa is strong enough for most LPR applications. The glue line around the OD prevents splitting. The geometry keeps it stiff, since it can't flex without also stretching.

Make the fit on both ID and OD a little on the loose side, just a little, so that there's no stress to speak of during assembly. That means relying even more than usual on good glue fillets, but the fillets are always where most of the strength of a joint lies anyway. Before it's in, it's delicate. Once the glue is fully cured, you're good to go.

The alternatives given above are better ways to go, but that wasn't the question.

Can we use balsa to make centering rings for model rockets?

The answer is yes.

 

[brockrwood]

If you are in a situation where you are required to use balsa, then yes, it can be done. An unconventional, but effective, way to do it would be to make a web. Basically, you put 3 or 4 strips of balsa running the length of the motor mount tube that extend out like fins inside the rocket to the inside of the body tube. Put one balsa centering ring on the front end of that, and it'll hold the ejection charge pressure inside, and the web behind it will keep it strong enough.

WW

I like this idea. I am going to try it. Basically make a balsa wood “cage” with two balsa centering rings strengthened by connecting ribs. A “cage” is an inherently strong, but light, shape, no? I should have taken mechanical engineering or materials science classes in college instead of philosophy. ;-).

 

[brockrwood]

Tim Van Milligan to the rescue! Tim has posted a video on Youtube about how to make simple, lightweight, cardboard centering rings stronger. See this link: One tip Tim provides that I did not think of is to put two smaller centering rings on the outside of the motor mount tube and push each of them up against one of the bigger centering rings. Then glue each smaller centering ring to its companion bigger centering ring and also to the motor mount tube. That should add a lot of strength to the bigger centering rings without adding a lot of weight. Thanks, Tim!

PS: Yes, this is really a "don't use balsa, just use cardboard" suggestion. This gets around the whole issue of using balsa for centering rings. At least for low power rockets. I don't (yet) build medium or high power rockets so I am not sure when one has to start giving up on paper, cardboard, and balsa, and start using stronger materials for a rocket.