Fin material

[chriswaterrockets]

Hi
until now, I've made my fins out of cardboard, not too thick and not too thin.

DSC05867.JPG

I have three fins, and as you can see, I "open" them a bit. That makes them a lot stiffer and doubles the fin area. But:
The problem is when they get wet, they are useless. They then bend so easily, that they are just useless. So I thought about wrapping them in a waterproof foil, but before I started, I wondered if there is any plasticlike, light material I could use.
So, what do you guys make your fins out of?
greets christian

[RaZias]

I once was going to try to make fins from the "exit signs" that are avaiable at the chinese shop (or at the AKI shop).

I use a circular fin (a bottle without the top and the bottom) 1/2 meter below the rocket suported by 2 very thin rectangular sticks, it´s the most stable thing I ever seen.
It goes always straight and it only changes his course during the fall down.

I haven´t putted water in it I just made some tests with air at 100 psi (looks like I fixed the air escape problem in the laucher but still there is a little air escape).
I am just saying that because I don´t know if not putting water makes it more stable.

[dongfang]

Hi,

I use 6 mm Depron for some of my fins. I make them double, like yours. It's a foam material that is pretty strong, and is used for making model aircraft etc. Try email or call the nearest hobby story and hear if they have it.

For small fins, I just use a single sheet of 4 mm balsawood.

In my experience, a small leak under water will cause the pressure to drop much slower than when it is above the water. But of course you will lose some water instead. I had an underwater leak in a rocket; I just overfilled it a little, and by the time it was ready for launch, it had lost the surplus water.

Regards
Soren

[reno1]

Hi Christian, Here is a pic. of some of my rockets and the material that I use. On the left are two FTC rockets, one water and the other solid fuel, on both I use (FOR SALE SIGNS) but you have to uses the BIG signs, the small one are too thin. You could use 1/16th plywood, like what is in the middle. The green fins are for a 2L. rocket and are made out of a small trash can that I got from a dallor store. Hope this helps. Later Reno

[dongfang]

Hi,

And here are mine. I was working on a set of Depron fins, just today.

Regards
Soren

[RaZias]

You can make your fins by cutting a Tupperware cube with a hot knife.
First you cut the squares then you cut it with the desire shape with the knife.

With a steel file tool you can erose it in the parts that have extruded plastic.

Anyway the problem will be to glue the fins.

[RaZias]

Here is a example of a circular fin.

I don´t know if glueing circular fins (with 1/3 of the rockets height) around the 1/3 lowest part of the rocket makes it more stable.

You can even put the circular fins with the guide-tubes of your launcher entering inside wich one of them.

circular fin 2.jpg (16.44 KiB) Viewed 413 times

[Tim Chen]

We use balsa wood and foam core for our fins. I haven't see anyone else mention foam core. It comes from art supply stores and is available in different thicknesses. It can even be sanded to air foil shapes if you like. It's not as tough as other materials but it is the stiffest and lightest thing we found.

[Spaceman Spiff]

Hi Christian, Here is a pic. of some of my rockets and the material that I use. On the left are two FTC rockets, one water and the other solid fuel, on both I use (FOR SALE SIGNS) but you have to uses the BIG signs, the small one are too thin. You could use 1/16th plywood, like what is in the middle. The green fins are for a 2L. rocket and are made out of a small trash can that I got from a dallor store. Hope this helps. Later Reno

Reno1,

How do you like the performance of the rocket fins when mounted at a tangent to the body tube like you have in the photos? Is there a advantage to mounting them in this way? It looks like it would be easier to mount them this way but it looks like the fins would need to be larger to get the same stability. I bet it might help prevent the rocket from spinning because alignment of the fins is insured by the body tube. What are your experiences with them?

[Cloud Dancers]

Has anyone here used bottles to make circular fins? You just cut the top and bottom off the bottle and glue them to the rocket in place of normal flat fins. Very easy.

[reno1]

Spaceman Spiff, The performance is great due to the fact that FTC water rockets CG is so far in front of the CP, that the fins can be small. Just make them a little longer for mounting. The rocket flies straight up, but spins alot on the way down, but a swivel takes care of that! Great fins because of ease to mount and they look cool! :P Later Reno

[Tim Chen]

Spaceman Spiff, The performance is great due to the fact that FTC water rockets CG is so far in front of the CP, that the fins can be small. Just make them a little longer for mounting. The rocket flies straight up, but spins alot on the way down, but a swivel takes care of that! Great fins because of ease to mount and they look cool! :P Later Reno

Crosswinds will make fins like this spin a lot because the fins resemble the buckets on a paddle wheel. Not the kind on a padddle boat, but the kind on a water powered sawmill from long ago.

Air from the side will spin the rocket. This design could be of use to anyone who launches in a windy area because it looks like the spinning would help stabilize the rocket in a breeze so it wouldn't deflect off course. The spinning give gyroscopic stability too but the smaller fin area would be less prone to blowing off course.

In the case you didn't want the rocket to spin at all, I bet you could mount a souble fin set on the bottom with each set going the opposite way to cancel out the paddle wheel effect.

I'm getting a lot of ideas from this discussion!

[chriswaterrockets]

Wow. I never thought so many people would post replys to my topic.
Many, many thanks to all of you!!
regards christian

[The Mooseheads]

Wow. I never thought so many people would post replys to my topic.
Many, many thanks to all of you!!
regards christian

It's really great to see everyone getting excited about this subject. Sometimes we assume a basic concept is no longer considered important and we don't bring them up for discussions thinking nobody would be interested. I think that materials and techniques advance over time and that clever people like us invent newer and better ways of doing even the basic things. It's what makes this stuff so addictive.

[reno1]

Has anyone here used bottles to make circular fins? You just cut the top and bottom off the bottle and glue them to the rocket in place of normal flat fins. Very easy.

Here is a set of tube fins for a FTC rocket. The fins are made out of FTC material. Pros: easy to make, easy to install, makes a cool sound when flying, and looks really cool Cons: none! Later Reno