Mounting To Fiberglass?

[stan]

When mounting items to fiberglass, is the process the same as mounting to timber? i.e. pilot hole then stainless self taper screw (with silicone) or are there any special tricks?

I am wanting to mount a bilge pump with a water pickup for a live bait tank.

Thanks for any advice.

Stan.

[pjbink]

You have to careful when drilling into the transom. Drill holes can let water get to the wood core and lead to dry rot which can ruin the transom and cost thousands in repairs. Heres a way of avoiding this problem:

http://members.toast.net/boatguy/drill.htm

Plug Method. This is highly recommended for any hole below the waterline, or in any hole that has coring material. Refering to the drawing below:

Step 1. Drill the hole a bit larger than you need. A good estimate is a minimum of 50% larger. For instance, if you need a 1/2in hole, drill a 3/4in hole. If you are going to screw a something into the hole, a larger hole is even better.

Step 2. Create a plug by sealing one end of the hole, then pour mixed epoxy into the hole - thereby creating a plug. There are many formulations of epoxy, and generally, the slower curing epoxies are stronger. If you are screwing into the hole, consider a slower epoxy. Otherwise, use a fast cure epoxy to prevent excessive dripping out of the hole.

Step 3. After a minimum of 24 hours (longer if a slow cure epoxy is used), drill the hole in the center of the plug the finished size you need. This creates an epoxy sleeve and completely protects the raw edge of the fiberglass sandwich.

Step 4. Attach the screw, bolt, or fitting with bedding compound by using the Bedding Method described earlier.

[stan]

You have to careful when drilling into the transom. Drill holes can let water get to the wood core and lead to dry rot which can ruin the transom and cost thousands in repairs. Heres a way of avoiding this problem:

http://members.toast.net/boatguy/drill.htm

Plug Method. This is highly recommended for any hole below the waterline, or in any hole that has coring material. Refering to the drawing below:

Step 1. Drill the hole a bit larger than you need. A good estimate is a minimum of 50% larger. For instance, if you need a 1/2in hole, drill a 3/4in hole. If you are going to screw a something into the hole, a larger hole is even better.

Step 2. Create a plug by sealing one end of the hole, then pour mixed epoxy into the hole - thereby creating a plug. There are many formulations of epoxy, and generally, the slower curing epoxies are stronger. If you are screwing into the hole, consider a slower epoxy. Otherwise, use a fast cure epoxy to prevent excessive dripping out of the hole.

Step 3. After a minimum of 24 hours (longer if a slow cure epoxy is used), drill the hole in the center of the plug the finished size you need. This creates an epoxy sleeve and completely protects the raw edge of the fiberglass sandwich.

Step 4. Attach the screw, bolt, or fitting with bedding compound by using the Bedding Method described earlier.

Thanks mate, much appreciated. Glad I asked.

[lancer]

Stan

Consider buying a piece plastic chopping board say 2- 3 cms thick and if its only going to have the pump on it, buy some sikaflex from Bias boats and put the board on the transom where you want it. Make the sikaflex thick.

Use small stainless steel screws to attach the pump to the board.

This way you dont even drill the fibreglass to create a problem.

Also you can remove the board later by slipping a long knife or blade under it.

To be on the safe side if the sikaflex lets the board go, make sure you use a big cable tie down attached to something solid near the pump so that the pump does not fly inside the boat at the end of the cable.

I used this on my old fibreglass boat and if you make the board big enough I had my sounder and pump on the board, the other thing is that you can adjust the positions of the sounders etc without worrying about drilling into the transom.

Dave

[stan]

Stan

Consider buying a piece plastic chopping board say 2- 3 cms thick and if its only going to have the pump on it, buy some sikaflex from Bias boats and put the board on the transom where you want it. Make the sikaflex thick.

Use small stainless steel screws to attach the pump to the board.

This way you dont even drill the fibreglass to create a problem.

Also you can remove the board later by slipping a long knife or blade under it.

To be on the safe side if the sikaflex lets the board go, make sure you use a big cable tie down attached to something solid near the pump so that the pump does not fly inside the boat at the end of the cable.

I used this on my old fibreglass boat and if you make the board big enough I had my sounder and pump on the board, the other thing is that you can adjust the positions of the sounders etc without worrying about drilling into the transom.

Thanks Dave, that gives me another option.

Much appreciated.

[vision21]

Buy yourself a counter sink tool, it looks like an upturned round triangle with a cutting edge. First drill your hole then use the counter sinker to cut your fibre glass so when you put the screw in it dose not lift the fibre glass edges.

Tony

Edited December 5, 2007 by vision21