Best motor mount epoxy / cement ?

[chipgibbs]

Ran my Cheetah today and flipped it once. When I got home the motor mount was broken free on one side from the hull. The "G-flex" epoxy joint came completely off the hull. I know I sanded the area before I mounted this in. No damage but, I want to be sure it stays in place.

What is the best method & product to use for the motor mount to hull joint?

Thanks guys

CG3

formerly Chip

[Mike Caruso]

Preparation!!!!
I don't know which type will be best for your application, but preparation is #1 I found out the hard way. Someone who does will be along soon.
Mike

[LOVE6S]

I will be watching this thread, as I just got some of the g flex myself and was going to use it on a couple of builds that I am doing, properchopper, Tony, had said he really liked the stuff, has anyone else been useing it? He makes a dam around the mount, probally not the best for looks, but I bet it helps alot, Shawn.

[Eyekandyboats]

I use g flex at my marina ALL. The time
I mount swim platforms. Ladder systems, rails, Everything with that stuff. We use it for engine mounts when doing a engine re build with removing the mounts from the stringer. We pile that stuff in the holes when we drop the mounts back down.
We use it for thru hull fittings as well. Quiet choice exhaust when I fit it to boats. Under water lights. I'd use it!


Sent from my iPhone 5

[chipgibbs]

I have been using G-flex for years on my rc sailplanes and never been able to get it to fall apart. I just wanted to know what the other builders are using.

CG3

[LOVE6S]

Sorry, if I might have thrown your thread of course, I just want to use the best I can, sounds like its good stuff, it would be interesting to know what other people use, as it is so important to have stuff stay put, Shawn.

[properchopper]

I will be watching this thread, as I just got some of the g flex myself and was going to use it on a couple of builds that I am doing, properchopper, Tony, had said he really liked the stuff, has anyone else been useing it? He makes a dam around the mount, probally not the best for looks, but I bet it helps alot, Shawn.

Chip, Somethin' aint right. Do this when you re-mount the motor. You won't see it when the boat's out on the water

cheetah builds133.JPG

[chipgibbs]

Thanks Tony, I've checked that system out on another thread. The G-flex came off the hull and all the epoxy was left on the mounts. Clean break.
I've removed all the hardware and have added a carbon pad in the motor mount area, 5" x 6". I sanded the area with 180 and wiped it down with alcohol before putting the carbon down with Z-poxy.
Tomorrow, I'll figure out how I'm gonna attach the motor this time.

IMAG0906.jpg

CG3

[JimClark]

What kind of alcohol did you use maybe Acetone will be better

[tlandauer]

What kind of alcohol did you use maybe Acetone will be better

+1 on Acetone, if using alcohaol, use only Denatured Alcohol.
I also like the epoxy dam Tony makes. Here is my version:

DSCN2307_1779.jpg

[Rocstar]

I've had a few nasty crashes at 80+mph with heavy motors mounted by the face only and G-Flex has held up so far. Something else is up...

[Eyekandyboats]

Must have been the way it was prepped.
i have actually put a full swim platform on a boat with G flex, not able to drill into the hull due to access, this is a 20 foot boat, platform was 3 feel long and the width of the boat.
3-4 people can stand on it with out even a slight flex.
alcohol for cleaning is not recommended for Sika or Gflex for sure. acetone is much better or clean-sol.

[chipgibbs]

I used denatured alcohol only but, I have some acetone too. In my opinion, the dam method helps the bond by raising the level of the epoxy so it can flow thru the holes in the motor mount. I don't think it will help the bond to the hull. If the stuff doesn't stick to the surface, it won't matter how much you put or how deep the dam is.

CG3

[keithbradley]

I used denatured alcohol only but, I have some acetone too. In my opinion, the dam method helps the bond by raising the level of the epoxy so it can flow thru the holes in the motor mount. I don't think it will help the bond to the hull. If the stuff doesn't stick to the surface, it won't matter how much you put or how deep the dam is.

CG3

I think that's a logical conclusion. If you aren't increasing the area or the friction of the area that you are bonding to, it's not going to make a difference.
It's possible that the hull wasn't scuffed enough, or there was something on the surface that the alcohol didn't remove. I've had hulls where stick on things like velcro would just fall off of as soon as you apply them. I think maybe sometimes mold release, or something of that nature gets into the hull. Make sure you sand it really well before you put the cloth in there, and apply your resin to the hull BEFORE you put the cloth in.

A couple of other things that can cause your motor mount (or other components) to come loose:

Flex in the tunnel-
If your tunnel flexes too much, either because the hull is too weak, or you just had a really unlucky crash, it can break the bond. This is still only something that exposes the weakness in your bond though...a really good bond will actually stiffen the tunnel in that spot so it doesn't flex there.

Improper epoxy mixture-
If you get too much hardener in the mixture it can make the epoxy brittle. This can cause it to crack and break easier.

Motor or driveline out of balance-
If something causes a severe vibration it can shake the mount loose over time. Typically this will lower RPM as well.


If you want the best bond you can get, doing an inlay with your choice of fabric, then using the same type of fabric and resin at fillet joints can't be beat. That said, it's not typically needed for that type of mount.

[capnswanny]

West Systems epoxy calls out Acetone by name as prep and I've used it for 20 years without fail. I'd also recommend roughing the area with very course grit to increase the effective bonding area on the hull. The more surface it has to bond to, the better.
My $0.02 :)