Fin alignment problem? Please help.

Hi,

I am working on a 4" fiberglass build, and have recently installed the fins. The tube was pre slotted, so I will assume that the axial alignment of the fins is good. Now that the epoxy has cured, I have noticed that two of the fins are slightly canted to one side. Is this going to be very detrimental to the rocket's performance? I have never had this issue before, and am concerned. Thank you. :y:

I had a similar SNAFU, and I was told that as long as they aren't twisted (thus roll inducing) the answer is no.

To prevent this from happening again, you can make a jig to hold the fins in proper alignment. I personally like the tool available from payloadbay.com.

K'Tesh said:

I had a similar SNAFU, and I was told that as long as they aren't twisted (thus roll inducing) the answer is no.

To prevent this from happening again, you can make a jig to hold the fins in proper alignment. I personally like the tool available from payloadbay.com.

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This is really cool, thanks for sharing

K'Tesh said:

I had a similar SNAFU, and I was told that as long as they aren't twisted (thus roll inducing) the answer is no.

To prevent this from happening again, you can make a jig to hold the fins in proper alignment. I personally like the tool available from payloadbay.com.

Click to expand...

I had forgotten about this link, thanks for posting it, as I can surely use it on two new builds I have working now.

Most of my rockets turn out like yours, and I am thrilled when they do. Unless you are going for an altitude or speed record, you'll be fine.

The fin tool from payloadbay works pretty good for one time use. I have used a few of them recently. I print full size then rubber cement it to foam core board, cut out, and go to town. Don't forget to cut notches where the fin meets the body tube for glue squish out clearance, or you'll glue your template to your body tube.

Banzai88 said:

The fin tool from payloadbay works pretty good for one time use. I have used a few of them recently. I print full size then rubber cement it to foam core board, cut out, and go to town. Don't forget to cut notches where the fin meets the body tube for glue squish out clearance, or you'll glue your template to your body tube.

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I've still got every guide I've printed... I reuse them all the time. Oh, and good reminder about the notches. The first time I made a rocket with one, I very nearly did glue it to the rocket.


After cutting out the guides, I often lose the info as to what body tube size and fin size they were meant for, so I'll write that down on the guide with a sharpie. That way, there's no confusion if it's for a BT-56 or a BT-55, or a 2.5" PSII tube or a 2.6" BT-80 tube, and I'll always know if it's a 1/8", 3/32", or other fin width guide.

That won't affect performance at all. The slots kept them straight where it matters.

In the future you can cut a fun jig out of some foam core board with an exacting knife. I have several in different sizes and fun configurations.

Damaged beyond repair. Please mail directly to me for proper disposal. Thank you.

BayouRat said:

In the future you can cut a fun jig out of some foam core board with an exacting knife. I have several in different sizes and fun configurations.

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That is exactly what I do. Get out my old school drafting tools, lay it out, and cut it out. Works great.

I use adjustable parallels and do them one at a time. Measure the fin can diameter, subtract the fin thickness and divide by 2. Set the parallel and you're good to go. In this photo, I did not have a parallel tall enough. So I had to subtract the thickness of the aluminum plate. These fins came out parallel and square to the fin can axis easily within .001.

By the way, the beans are good for a little added boost.