HyperLOC 835 warped fins

I decided to build this rocket last week but found that all three fins are both warped and twisted. I did my usual wet/press/repeat tricks, but the fins soon returned to a deformed state. I'm sure Barry would send out replacement fins, but I started thinking about going away from plywood. The fins are 1/8" thick and the booster is slotted, so I'm locked in at a specific thickness. Carbon fiber would look cool but is certainly overkill on a cardboard rocket from a materials standpoint. FG is more reasonably priced but I have a couple experiences with FG fins being slightly warped. Either option forces me to use epoxy (despite the LOC instructions I decided to build with wood glue). There's no guarantee that replacement fins - or ones I cut from ply myself - would remain flat.

Or I could just go bananas and sleeve the whole rocket. That would be purely for aesthetic purposes. A 6' CF/FG sleeve would look great with gloss CF fins. This line of thinking also starts to cost more thancwhat I paid for the kit. Let's table that for now.

Seems the practical choice is a sheet of FG. Anyone care to weigh in on their experience with sheet goods? I'm worried about getting a warped sheet but not sure if that is a reasonable concern. I would likely source from Rocketry Warehouse but am open to alternatives.

Thoughts are welcome.

Barry has done FG fins before. Maybe you could approach him and only have to pay the difference to get the 1/8" fin fiberglass upgrade.

You could glass your warped plywood fins, stop the glass at the tabs and you won't have to open the slots any. The preferred way would be vacuum bagging but you could probably get by placing them between two nice flat surfaces and weighting.

dixontj93060 said:

Barry has done FG fins before. Maybe you could approach him and only have to pay the difference to get the 1/8" fin fiberglass upgrade.

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That is a great idea. I checked the LOC website for replacement parts and didn't see any FG option so I appreciate you enlightening me to this.

Crash-n-Burn said:

That is a great idea. I checked the LOC website for replacement parts and didn't see any FG option so I appreciate you enlightening me to this.

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Yeah, call Barry. He made a set for me for my L3 build.

I've had warped ply on more than one occasion. here's how I deal with it...

Apply 1 layer of fiberglass on each side of the fin(s). While epoxy is still wet, place them between 2 panes of thick glass (fairly cheap at a window/glass store). Be sure to use parchment paper or wax paper between the FG and the glass (on both sides). Once inserted, apply substantial weight to the top pane of glass. Leave it there for a day or two and trim the excess FG. The fins will be perfectly flat.

As far as the pre-slotted airframe, you can use a Dremel to expand the slots and make them fit.

Just a quick update on this one. I did order the fg fins from Barry and received them really fast. Great customer service as always. The fins fit nice and everything was dialed in for use - no need to adjust the fin tab depth, etc.

I just couldn't bring myself to put them on the rocket. I don't know, maybe it was one of those purist, all-wood rocket moments. They sat in the rocket dungeon for a month and every time I looked at them it just felt... wrong.

This past weekend I bought a sheet of 3/16" BB ply and cut another set of fins. I had to expand the slots on the booster to accommodate the thicker fins, but had everything ready for glue up in less than an hour. Now they are on and look pretty good. I even did all the external fillets with epoxy - because I'm a fraud and a hypocrite Anyway, I thought that I'd share my indecisiveness in the hopes that someone doesn't find it completely useless information. As for the orphaned fg fins? They are a nice excuse to buy more fg tubes.