This blog covers the day to day progress of water rocket development by the Air Command Water Rockets team. It is also a facility for people to provide feedback and ask questions.

Sunday, October 10, 2010

Fins and Fiberglassing

As a part of the work we are doing with Polaron G2, we are looking at different fin materials.

This week we are comparing 3 different ones. The first one is a regular 4mm 3-ply plywood fin. This fin is very tough, but the main drawback is its weight. At 74 grams it is the heaviest. Thickness is 4.2mm.

The second one we tried making out of two 1.5mm sheets of balsa wood glued together at 90 degrees to each other with PVA glue. We then put one layer of 200gsm fiberglass on either side. Epoxy resin was used for this. The fin is quite tough and weighed in at 43 grams. The thickness is 3.9mm but the main drawback is the amount of work involved to do this and the higher cost.

 The 3 fins tested. Left to right: corriflute, balsa/glass sandwich, plywood.

The last fin is made from corriflute, the material we have been using until now. It weighed in at 25 grams, but has a thickness of 5mm. It is quite tough, and has a good finish, but the main drawback is that it is made from polypropylene and hence harder to glue and paint. The leading and trailing edges are also harder to create nice and smooth.

So far the balsa sandwich is probably a good compromise, unless we can find some nice lightweight plywood.

We have also spent some time this week getting Acceleron V rebuilt and serviced so it can be launched again. We also did a 50psi leak check. We'll try to launch it again soon just for fun.

We were supposed to go out to the NSWRA launch today, but after driving half way there in pouring rain, we decided to turn back. As we got back, the weather cleared up but the wind had picked up. So we went back to the workshop and fiberglassed 3 of the spliced-quads. We are going to give them at least 5 days to fully cure before pressure testing. We are going to try to push them to 270psi for the 250psi launch pressure. We'll see how much they'll actually hold.

 3 x 5.3L spliced quads wrapped in fiberglass.


Anonymous said...

Air Command,

I guess you would have tried the 2mm Coriflute - with pen inner on the leading edge for aerodynamics.

I think the benefit is that it is cheap and easy to make (probably under 20 grams). Does not need to be strong. You can superglue to the bottle - and it it has a hard landing - it just breaks off at the bottle perfectly intact - and can be glued on with superglue again in ~2mins with little effort. ie. you could also just fibreglass the 2mm corriflute if you like a better finish. Or dip it in a hardener if you wanted to harden up the internal ribbing..This material would be hard to beat frf lightness.

Charlie H

Anonymous said...

Air Command - Another thought. As boring as they are ring fin's behind the rocket to stabilise do not protrude and have less drag then normal fins. Also if the jet is is directed through the ring fin - any air on the top side may be sucked through by venturi - further reducing drag on the rocket

Anonymous said...

Last comment - I also note DAY 100 is something spectacular going to happen???? water rocket fireworks - Apogee air explosion with confetti (LOTS). The new Big Rocket?? What about a glow in the dark silume charge instead of water??

George Katz said...

Hi Charlie,

Thanks for the suggestions. I think the 2mm Coriflute by itself may be too thin. We really need to have the fins as stiff as possible as there will be significant forces on them when the rocket is traveling 350km/h+. (as the simulator says)

But reinforcing it with fiberglass may work. I think we have some 3mm stuff on hand, so we may give that a go.

George Katz said...

We hadn't planned anything special for day 100. It's only an update number rather than a milestone. Perhaps we can do something on the 5th anniversary of our first rocket launch? That's coming up mid next year. :)

doctorxice said...

Good morning, could do me a brief summary of how the quads lining fiberglass, thanks

George Katz said...

Doctorxice, I've posted some more info on how the quads are made:

doctorxice said...

Hi George, meet my new rocket, I hope you enjoy it as I enjoy yours, congratulations on your work