Another throwing blade question. - RC Groups
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Jul 23, 2012, 11:16 AM
Time for me to Fly...
Mr. Wiz's Avatar

Another throwing blade question.

I followed Tom's recommendation in the thread I started the other day. That worked great, Tom. Thanks!

Now, the blade came out of my Fr3aK yesterday. It just came loose and slipped right out of the hole. Here is the question: Should I grind off the old CF patch around the blade hole and install new or am I OK to just epoxy the peg back in the same hole? It seems to me, I'd want a new patch with a new fillet of CF and epoxy but I want a back up of that opinion before I go to that much effort.

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Jul 23, 2012, 11:34 AM
Walter Roos
ROOSWH's Avatar
Don't know if this is the kind of answer you are looking for but,

Usually after flying awhile the epoxy on my blade will break free and I expect that to happen. A bit of Regular CA around the peg is then applied and that fix ,more often than not, is permanent. Seems the CA sticks to the blade better than the 15 minute Epoxy Splooge mixture.

If your new blade is similar to the size of the old one, I would just epoxy/splooge it in with a tiny bit of a fillet on the top and bottom, then expect it to break loose at some time, then CA it in for the final fix.

works for me.,

Jul 23, 2012, 11:43 AM
Time for me to Fly...
Mr. Wiz's Avatar
OK Walt. I'll try just glueing it back in. Nothing really broke except the bond.
Jul 23, 2012, 01:39 PM
Duane, LSF IV
Wazmo's Avatar
I have one of Oleg's blades in mine, and it kept loosening when it was just glued in with a carbon patch. I had removed some of the foam between the skins around the blade hole, and filled with epoxy and milled glass fibers. Several times it would break loose after a couple days flying, and I had to CA in place again. I ended up adding a fillet of epoxy thickened with glass fibers and cabosil, on the top and bottom. I think I used the end of a popsicle stick to shape the fillet, and carefully remove the excess from the carbon patch with a paper towel. Since then, the blade's been solid.
Jul 23, 2012, 11:11 PM
It's a mere flesh wound!
Buddy Roos's Avatar
Be sure to sand the peg where the glue is going to go. They almost always have a little mold release left on them.

For that matter, I always sand anything made of carbon fiber before I glue it. The one exception being carbon fiber cloth!

Jul 24, 2012, 08:52 AM
Walter Roos
ROOSWH's Avatar
btw :
I assume that you put a hard point in the tip for the Blade.

And if so, you can use regular thin CA. If there is no hard point, and you have a regular foam wing, then Regular CA will eat up the tip foam, but a hard point keeps the CA away from any foam.

Good luck with your repair,

Jul 24, 2012, 08:56 AM
Time for me to Fly...
Mr. Wiz's Avatar
I just sanded up the blade and epoxied it back into the hole where it was. It feels as strong as the original if not better. I think the original installation was done with CA. That's the way it looked. I used Pacer Z-Poxy laminating resin and FWIW, it was a still a tight fit in the hole.
Jul 24, 2012, 01:32 PM
Registered User
I don't know if this applies to Z-Poxy, but some laminating epoxies don't stick as hard to well cured composites as some adhesive type epoxies do. Not sure if this is the best solution, but lately I've been smearing a bit of the adhesive type onto old laminates before putting glop made with laminating epoxy on top of it.
Jul 24, 2012, 01:33 PM
Time for me to Fly...
Mr. Wiz's Avatar
If it works loose again I'll use some JB Weld.
Jul 24, 2012, 01:48 PM
Father of Fr3aK, DLG Pilot
tom43004's Avatar
Rubberized CA is great for this too.

I second the "sand it in the area you bond it" discussion, but with throwing pegs always use lighter grit paper and sand lengthwise. Heavy sandpaper or crossing the unicarbon "grain" can lead to failure of the blade.
Jul 24, 2012, 05:21 PM
Registered User
It's probably a really good idea at some point to use isopropyl alcohol to thoroughly clean off the peg and the inside of the hole. Maybe use pipe cleaners or yarn for the hole? Not just because of mold release. It seems likely that a mixture of sunscreen and sweat has seeped in as well.

I once laminated some precured carbon onto some wood spars using a good quality laminating resin. (Custom mix from a boat builder I know.) They peeled off quite easily, and the epoxy mostly came off of the carbon. I did a sample with 30 minute epoxy and they stuck tenaciously. For the really picky, 3M makes some high quality epoxy that comes in a double tube for electronics purposes. I'm going to try that next. Shelf life isn't the greatest, though, as I recall.
Jul 24, 2012, 09:26 PM
The Lone Sloper
Originally Posted by Mr. Wiz
If it works loose again I'll use some JB Weld.
I use 5 min JB weld, solid as rock.
Jul 24, 2012, 11:17 PM
Father of Fr3aK, DLG Pilot
tom43004's Avatar

Two of the three mold releases I use regularly are not soluble in alcohol. One is soluble in water. Depending on who / how the peg was made, very light wet sanding may be the only way to positively remove it.
Jul 26, 2012, 07:28 PM
Registered User
Hmm.. I usually think of mold release as PVA, but I guess that makes me a Luddite. Those other two don't come off with paint thinner or something? Goo Gone? Nothing wrong with wet sanding, of course.

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