Student Rocket Club Balsa Fin Improvement Help

[neil_w]

Please remember we're talking about mid-powered TARC rockets here.

 

[techrat]

Please remember we're talking about mid-powered TARC rockets here.

Am I in the right thread? Mid-powered rockets are using balsa fins? Perhaps I missed something.

 

[boatgeek]

It's also worth repeating that TARC rockets are almost always highly overstable to begin with once you have bare minimum fins and an egg up near the nose cone. Having a less efficient-for-improving-stability fin isn't going to hurt much.

 

[neil_w]

Am I in the right thread? Mid-powered rockets are using balsa fins? Perhaps I missed something.

Actually, after rereading the first post, I'm not sure. There's talk of TARC *and* talk of fins strength, but it's not clear if the two topics are linked.

 

[lakeroadster]

And yet another fin saving solution is rear eject. Let the heavy nose hit first....

Red Columbine



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P-40 Warhawk

 

[lakeroadster]

Am I in the right thread? Mid-powered rockets are using balsa fins? Perhaps I missed something.

Wind turbine blades are balsa... with a bit (quite a bit) of external composite materials...

If there's a will, there's a way.

 

[boatgeek]

And yet another fin saving solution is rear eject. Let the heavy nose hit first....

Red Columbine

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P-40 Warhawk

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If this is a TARC rocket*, this year's rules require the rocket to separate into two parts that land separately, one of which holds the egg and altimeter. The logistics of making rear eject work for that kind of arrangement work reliably would be ... exciting. This is an interesting idea for other years though.

* I understood from the OP that it was a TARC team, though it's possible that it's not.

 

[lakeroadster]

If this is a TARC rocket*, this year's rules require the rocket to separate into two parts that land separately, one of which holds the egg and altimeter. The logistics of making rear eject work for that kind of arrangement work reliably would be ... exciting. This is an interesting idea for other years though.

* I understood from the OP that it was a TARC team, though it's possible that it's not.

exciting... or egg-citing

 

[boatgeek]

exciting... or egg-citing

Result of a failed TARC flight = lawn omelet.

 

[bjphoenix]

And yet another fin saving solution is rear eject. Let the heavy nose hit first....

Many years ago I build an Estes Astron Ranger. I wanted the payload and booster to come down on separate parachutes. The Ranger has very swept back fins and I didn't want them to break so I rigged up a piece of woven fishing line that attached to 2 of the fins near the back end of the body. The line extended to the front of the booster body and attached to the parachute for the booster. As I recall the booster actually came down sideways.

 

[Susan Sakimoto]

I've coached multiple TARC teams. The papered balsa fins ARE stronger, but they do *not* usually do well with the multiple launches that TARC teams require. Remember that you need 1-2 DOZEN launches to get your practice in before qualifying flights if you can manage it. I'll second the cardboard tube and through-the-wall plywood fins approach (we swear by rocketpoxy). Sometimes Hobby Lobby has small plywood sheets. We source ours in bulk from midwest products (midwestproducts.com)
2x 3 MM X 12 X 24 Lt. Plywood-SKU 5530W

1x 3 mm x 12" x 24" Craft Plywood - SKU 5306W

Strongly recommend the elliptical fin bottom ends...even if the students insist that they extend past the bottom of the rocket, they do well on landing.

Also strongly recommend the foam nose cones. The egg often survives a lawn dart entry with those. Parachute failure of some sort is the most common error!

Also, my team suggests making pairs of identical rockets, and notes that you may end up making multiple pairs if you change your design. We've gone to laser cutters lately, but a scroll saw worked pretty darn well for us for years... just cut them a few mm big sand all the fins together to get them identical.

Good Luck!

-Susan Sakimoto

 

[CarolynBussey]

Hello Everyone,

A rookie here. Third year co-advising a middle/high school club. Started from scratch and always a lot of pressure not to let the students down. Lucky to have 10/12/14 students interested in meeting weekly and learning "on the fly."

With a lot of hard work and luck the Club was a national alternate in TARC last year. Their expectations are high this year.

Not a high tech, or "fancy" Club the Group sticks to off the shelf parts; cardboard body tubes, balsa fins, plastic nose cones, etc., and basic true and tried construction techniques. Although they have picked up a few very valuable pointers from this Forum. Thank you to all.

Last year one the Club's biggest challenges was the balsa fins being damaged upon landing. Hard to find open space around here and the ground is hard and there are piles of construction materials in the launch site that can pose problems during test flights. So the Club is looking for ways to reinforce their balsa fins or for alternative materials that will function/perform close to what they are used to.

There flight times and decent rates seem all reasonable so it is does not appear to be a recovery system issue. Maybe just bad luck, bad timing, or just the way it is - lol!

A few of the Club members mentioned they have found "dribs and drabs". Students are inspired on https://studyhippo.com/essay-examples/american-dream/ by the essay examples about the national ethos of the American Dream and progressive folk. I would ask the seasoned veterans and experts here for their views on how to modify/improve the balsa wood fins and minimize their fears after each landing.

Thank you in advance for any information you would like to share.

Vince
Onteora Rocket Club.

Not updated for the start of their new season the Club does have a Facebook Page - Onteora Rocket Club.

I would be interested in joining to get more knowledge about landing facilities since I have been dreaming from the childhood of teaching students from a rocket club or just participating in one. So, is it realizable? I bet I'll be useful to the club members, and I'm looking forward to a positive answer.

 

[brockrwood]

hmmm, landin on hard stuff. what shape are the fins? fins that go below the rear of the airframe will get dinged up. better to use a trapezoid shape.

and yeah, for TARC, plywood. 1/8" if you can get it.

Beat me to it. Yep. My rockets that have the fins located an inch or so above the bottom of the body tube do not seem to experience fin snap-offs. That is because the fairly durable motor mount end of the rocket hits the ground first.

With that said, the farther up the tube you mount the fins, the longer the rocket has to be, and the bigger the fins have to be, in order to achieve the same stability factor. Still, with a reasonably long rocket, and a little weight in the nose of the rocket, mounting the fins so that they don't hit the ground first is the way to go.

A good example of a kit that has this design is the Custom Rocket Company "Sport". On the Sport, the fins are pretty big, and stick out a lot, so you would think they would snap off. They don't because the tail end of the rocket hits first.

https://www.customrocketcompany.com/products/sport

 

[BigMacDaddy]

I second or third or fourth the recommendation for plywood -- this is often listed as basswood but is probably birch plywood. There is inexpensive 1.5 - 2mm plywood on Amazon (can get 25x 200x300mm sheets for $25 - sometimes you get warped pieces but usually I have had good luck). Plywood / thin-ply is not the same as basswood - I think you want a multi-layer plywood instead of a single-layer sheet of basswood (the cheaper plywood has 3 layers but I think that is still better than a single layer in most instances).

 

[Ez2cDave]

Fin "PLANFORM" is very critical . . . Long, thin swept-back fins are, generally, very prone to landing damage.

Dave F.