Proline 4500 external fin fillets using a mask

My recent mini project has been to improve my external fin fillets. They have been good, but I really disliked applying masking tape and cutting the rounded ends with a hobby knife. I broke out the vinyl cutter and some vinyl mask (less adhesive than normal vinyl); here are the results.

Lighting leaves something to be desired and Proline is very hard to photograph. The result fillets look great from more than 6 inches away. The only flaws are where the two halves meet. This could be fixed with minor sanding, but I usually ignore the small rough spot.

Rocket is a Wildman Jr. fiberglass kit.


View from above. These are hand applied without the masking tape layer. The low tack adhesive makes for easy repositioning.


Additional masking tape added to protect against drips.


Some of the Proline 4500 is now added. I typically add much more than needed.


Epoxy smoothed with 1/2 inch copper coupler. Excess scraped back into container at first and wiped on towel at later stages. Only an initial dip in denatured for the coupler.


One fin unmasked, the other is still surrounded with the mask.


Detail of aft end of mask. I'm still deciding how I like to remove it best. The slit at the back allows me to carefully rip it off.


Pulling the mask off. I will go back afterward and remove the rest of the aft end soon.


Detail of forward end of mask. The mask rips cleanly at the front point of the opening.


Fresh fillets now curing. It took less than 10 minutes from putting on epoxy to this point. That includes putzing around with the camera and avoiding getting epoxy on it.


First set of fillets all cured. Not perfect, but really good. I didn't get one little spot on a rounded end but that can be fixed easily.

There are some definite benefits. All the fillets are symmetrical, the forward and aft tapers are nice and smooth (better than I got with masking tape) and these are good enough to leave as is. The Proline hasn't caused any mask to be left under the cured smears on the second half, but I make it a point to touch up the ends before it cures where I smear epoxy on the mask.

Is there any interest in production of these? I have an ample supply of the masking material.

Really interesting-how much do you think these would go for? How would you order them?

That's a great idea. I can make quick work of those with a laser cutter but I'd gladly buy them from you if you'll produce them.

I am interested.

I would imagine about $6 + postage for a set of 3 around this size. Ordering would be by length and width if you have direct measurements of the fillets (these were measured by scraping some of the copper off on the tube). If measurements weren't available, there is a bit of math that should get sizes very close. I still need to confirm the math with my actual results before relying on this. I'll be launching rockets a lot of the weekend, but I could make up a set for you if you would like to beta test.

Doug