Loc Precision Loc IV warped fins

[ascastil]

Building this for L1 cert. Noticed all the fins are warped. Tried straightening them with a steamy iron. It straightens them at first, let them dry overnight between 2 mirrors and some weights, still warped. Use them or ask for replacements?

 

[crossfire]

I would just ask for replacements.

 

[ascastil]

Im leaning that way too. Bought all the supplies to build a perfect rocket. Even a large guillotine fin jig. Might as well wait and put on straight fins. Is this common? Had 3 Estes kits with warped fins that I ordered around Christmas.

 

[Steve Shannon]

Im leaning that way too. Bought all the supplies to build a perfect rocket. Even a large guillotine fin jig. Might as well wait and put on straight fins. Is this common? Had 3 Estes kits with warped fins that I ordered around Christmas.

Warping is common with wood products which are sent from a place of one humidity to a place of another. If the warping isn't too bad you should be able to pull it out but you really have to go past straight so it returns to straight.

 

[MikeyDSlagle]

My Madcow Little John has warped fins. I still have to deal with that myself, very frustrating.
In the past I was able to get the warp out using bungee cords, an iron, wood dowels and a hair dryer. Will have to work out the process again. Ho hum. Luckily these aren't very bad. It's just one of those things.

 

[markkoelsch]

How much warp? If you lay the fins flat holding the root flat how much across the span?

 

[DAllen]

Warping is annoying but inevitable and may or may not be the manufactures fault. However, if you're willing to put a little work into it, it is very fixable. The way I've fixed warping is to fiberglass both sides of the fins prior to mounting and then sandwich the fins between two heavy and very smooth weights. To prevent the fins sticking to the weights I used a wax paper layer on both sides. A good weight to use are particle board shelves because they're rather dense and quite smooth. Keep the weight uniform and it works great. I bought some lightweight plywood once made from pine I think and it would warp like crazy as soon as I cut it. This method worked like a charm and the fins are still straight to this day.

For balsa or lighter weight woods glassing would be a tad over kill and I would imagine a similar method "papering" the fins would work.

 

[ascastil]

Im gonna go out and look for some fiberglass. Im bored, time to learn something new.

 

[DAllen]

Yeah that's pretty typical. Looks like you have some sort of filler on the fins. Sand as much of that stuff off as you can so there's good adhesion between the wood and glass. Also keep in mind, there's a trade off I failed to mention with glassing the fins; there might be more finish work involved depending on how picky you are on smoothness...

 

[ascastil]

Going to the hobby store to pickup some fiberglass today. What are the chances if done correctly when it dries the fins will be straight? I have 2 mirrors and 40lbs of weight or more if needed to stack on top of the fins.

 

[DAllen]

That's not a lot of warp to fix. I'd say if you follow the instructions your chances are good. I'd leave the fins between the weights for about a day longer than the directions say it takes to cure just so you're 100% everything is set.

And don't forget wax paper...

 

[ascastil]

#1, the glass did not fix the warp. Had it curing between 2 mirrors and 70lbs of weight directly on top of the fin.
#2, I love fiberglass! Shiny and stiff. Gotta master the technique. I like it.

Traced a template before I started. Gonna ask for replacements but I gave it my best to fix it. No worries, I learned a few things.

 

[DAllen]

I don't think you let it sit between the weights long enough. Like I said, I let mine sit for at least 24 hr longer than the directions says it takes to cure. Sometimes days. There's only about 12 hrs between your last two posts. Is the glass tacky at all?

Oh well...

 

[ascastil]

Yeah. The hobby store only had 30 min epoxy so thats what I used. Asked a friend and he said Ill just have to work fast.

 

[DAllen]

Yeah. The hobby store only had 30 min epoxy so thats what I used. Asked a friend and he said Ill just have to work fast.

If it's still tacky it isn't fully cured. Plus, 30 min epoxy works OK is not necessarily the best option for glass. I usually use the poly(whatever it is) resin.

Leaving it smashed between weights makes it cure slower - much slower.

 

[Steve Shannon]

Using epoxy without tight glass reinforcement would not prevent the wood from returning to a warped shaped.
There's always some spring back; that's why you have to pull the wood beyond straight.


Steve Shannon

 

[ascastil]

Thanks to Loc for working with me. They shipped some replacement fins out today and should be here Thursday.