CA soak fins: How, where, why?

[Ronz Rocketz]

I'm alegey building an EZI-65 for my L2 as well. I've been building it for going on 10 years. But I do think it will eventually prove to have been a good choice.

The paint should be dry by now.

 

[jqavins]

Well, the primer is.

 

[afadeev]

I have not seen a suggestion or response on using epoxy... say 1088 epoxy, on fins to strengthen them.

Epoxy is heavy.
If you (or the kit supplier) had selected balsa for the fins, they likely worried about weight.
Just papering both sides of a balsa fin doubles its weight (I measured and posted pics in another thread).
If you smudge epoxy, and let it soak in for maximum strength, you will increase the weight by more than 2x. More like 3x-4x. By which point, you might as well have used plywood or fiber-glass for the fin material in the first place!

Mix, squeegee (two ee’s?) on, hang to dry. Much more controllable as far as flow - just use tape to keep it off the root edge and peel before dry. Might have to sand a bit but should be nice and hard.

And heavy!

 

[Philip Tiberius D.]

Epoxy is heavy.
If you (or the kit supplier) had selected balsa for the fins, they likely worried about weight.
Just papering both sides of a balsa fin doubles its weight (I measured and posted pics in another thread).
If you smudge epoxy, and let it soak in for maximum strength, you will increase the weight by more than 2x. More like 3x-4x. By which point, you might as well have used plywood or fiber-glass for the fin material in the first place!

These are the stock fins - Bass wood ( I think) 35.6 grams average after, I think they were almost 33 on average before. I should have beveled the edges before but no big deal. Part of me wants a little weight so I keep it around 3k ft - I’ll build the Mach1 Momentum for altitude (full J) with a 75mm option.


And heavy!

 

[neil_w]

Just papering both sides of a balsa fin doubles its weight (I measured and posted pics in another thread).

With 1/8" balsa fins, I see about 50% weight increase with label paper. Just another data point. Where was the other thread where you measured?

 

[Philip Tiberius D.]

With 1/8" balsa fins, I see about 50% weight increase with label paper. Just another data point. Where was the other thread where you measured?

I didn’t start another, I had written it down on the paper covering my work bench. I was considering documenting the process but then my 6 yr old daughter started helping...

 

[Spitfire222]

I've only ever applied CA to the outer edges of balsa fins only as a quick and easy way to add a tiny bit of resilience to hangar rash and dings, etc. If I was so concerned about the strength of the fin that I was considering applying CA to all of it, I'd look into other materials, or actual structural reinforcement (e.g. thin veil fiberglass, etc).

 

[neil_w]

I've only ever applied CA to the outer edges of balsa fins only as a quick and easy way to add a tiny bit of resilience to hangar rash and dings, etc. If I was so concerned about the strength of the fin that I was considering applying CA to all of it, I'd look into other materials, or actual structural reinforcement (e.g. thin veil fiberglass, etc).

I agree. CA is most ideally suited for surface hardening and protection.

I confess I would be curious to see someone do some controlled testing of the strengths of various fin structures: plain balsa, CAed balsa, label-papered balsa, glue-papered balsa, etc. If I had the time I would do experiments like this all day because it sounds like fun.

 

[jqavins]

If doing that sort of experiment, one should not only do strength. For each treatment, test strength, stiffness, hardness, and density.

My internal conversations typically go like this: "I'm probably overthinking, but I'm a little concerned about the strength on this. Maybe I should switch to basswood. Nah, balsa'll be fine."

 

[Ronz Rocketz]

I also like thin CA on the edges because it fills the pores nicely and shows a nicer finish when painted. The downside is when it runs across the fin.

 

[jqavins]

I love the way thin CA wicks into places. I hate the way it runs. Runs across the fin. The fin-ger. Grrr.

 

[neil_w]

Except when doing something like CAing a nose cone, I use cotton swabs to apply CA. Yeah, I go through a lot of them, but no running.

 

[Ronz Rocketz]

I love the way thin CA wicks into places. I hate the way it runs. Runs across the fin. The fin-ger. Grrr.

Yeah, I always have to wear a nitrile glove on the hand holding the fin. I've actually burned a hole in the glove from too much thin CA. I'm also gonna start using goggles because I splattered a drop on the side of the lens on my new GoPro8.

 

[jqavins]

There are ways to get that off, but they'd probably f-stop up the lens worse.

 

[Ronz Rocketz]

There are ways to get that off, but they'd probably f-stop up the lens worse.

It’s off to the side of the lens. I used a hobby knife to scrape most off. It only shows because of the protective glass on top. For some reason, GoPro decided to make the 8 without replaceable lens.