Attaching G10 board to inside hull

[Jerry Woodward]

I bought some 1/4 inch G10 board to use as a mounting plate for a manual diaphragm pump to be attached to the underside of the deck in the bow locker. This should provide enough thickness to attach screws without going through the deck. I have a tube of 5200 and was thinking of using that. Does this seem reasonable or would you use epoxy?

[psk125]

1/4" does not seem thick enough for screws to have sufficient bury to hold a diaphragm pump for long, especially upside down. You do not want anything penetrating the deck at all because it WILL get wet - you're on a boat. That means your screws would need to be about 1/2" long? Bolts might work better than screws. Even then a thicker pad might be better. You should probably include fender washers under the bolt heads to spread the load and point them threads down so that you can tighten the nuts from below when you put the pump in place. Have not used 5200 but epoxy will certainly work if you can keep the G10 in contact with it place long enough for everything to set.

[Jerry Woodward]

Good point on the thickness. I could easily double or triple the G10 by gluing multiple pieces together. Which brings me back to the same question, epoxy, 5200, or something else? If I used bolts pointing down, I would need to countersink the heads into the G10 and than fix them with epoxy or something to keep them from turning.

[Spot]

Originally Posted by Jerry Woodward

Good point on the thickness. I could easily double or triple the G10 by gluing multiple pieces together. Which brings me back to the same question, epoxy, 5200, or something else? If I used bolts pointing down, I would need to countersink the heads into the G10 and than fix them with epoxy or something to keep them from turning.

Does it need to be a 'blind' installation? I'd be tempted to hang the backer plate and pump using some nice SS bolts with a large rounded socket head and locking nuts underneath. Hole prep for the the through deck hardware (drill-fill-redrill) would be a must.


If you want thicker G10, scuff the plates and epoxy them together before installing.

[psk125]

Thought some more about this last night. Why not just epoxy bolt heads to the underside of the deck with some dabs of epoxygoop? No need for G10 at all. Deck should be strong enough - you just don't want holes in it. Have used this technique for footrests in our kayaks. The trick is getting he bolts in exactly the right place for attaching the pump.

[Bowdrie]

Originally Posted by psk125

The trick is getting he bolts in exactly the right place for attaching the pump.

That is easily solved.
The bolts are put in the mounting holes first, with washer and nut on each side of the mounting holes.
Or a template can be made.
A scheme is developed to hold pump/template in place until epoxy sets up.
Once cure occurs, the pump/template is removed from the "studs" and additional epoxy can be applied to reinforce/strengthen the mounting.
Small squares of fiberglass fabric can be slipped over bolts and glassed to hull/deck to present a finished appearance.
Nuts and large/fender washers adjusted to provide flat-plane mounting so as to not strain the pump housing, then outside nuts/washers installed to mount pump.

[Bowdrie]

Now, would I use the method I described above? No.
I would not want studs sticking down from the underside of the deck that were more-or-less permanently attached.
Better would be to take a generous sized piece of marine grade plywood, (~3/4in thick,) and install stainless steel "T Nuts" thru the back side that matched the bolt pattern.
A properly sized "spade bit" can make a shallow recess so that the T-nuts cab be installed flush with the back side.
Then put something like Vaseline around the T-nuts to prevent epoxy from blocking the holes and epoxy the plywood to the deck.
If removal is ever necessary, the plywood can be chiseled off without damaging the deck.

[Madehn]

even simpler way-- use a piece of 1/2 inch G10--- drill and tap the holes for mounting bolts before mounting the pump-- epoxy the G10 in place using thickened epoxy OR use 5200 but the 5200 will need to set up for several days at a decent temp to reach full hardness-- drilling and tapping the G10 is super easy-- i just did 14 backer plates for thru hull installation on my boat in about 35 minutes with 5 or 6 bolts on each plate- the 5200 should be plenty strong to use and might be easier than epoxy-- when mounting the plate screw the bolts in without the pump until they are just below the surface of you are gluing-- if you want you can use a couple of dab spots of 60 second epoxy to hold the board in place while the rest of epoxy or 5200 dry. easy and professional looking and easy to take pump on and off if needed

[Madehn]

forgot to mention- thoroughly wipe down the deck and the G10 with acetone before trying to glue with anything-- new G10 sometimes has an amine type blush on it that will prevent gluing-- ideally wipe down, sand to get a little rougher surface then wipe down again and glue-- do NOT just sand as it will drive the blush/wax stuff into the surface of the g10 and not clean it well enough to get a good bond

[jhulmer]

Jerry
I always use epoxy. Be sure to clean and sand the surfaces first there is probably wax from the layup.

Another "Pro trick" I learned is to use hot glue in the middle to hold the piece in place until the thickened epoxy cures.
Jim

[Spot]

Originally Posted by Madehn

forgot to mention- thoroughly wipe down the deck and the G10 with acetone before trying to glue with anything-- new G10 sometimes has an amine type blush on it that will prevent gluing-- ideally wipe down, sand to get a little rougher surface then wipe down again and glue-- do NOT just sand as it will drive the blush/wax stuff into the surface of the g10 and not clean it well enough to get a good bond

I am also a fan of this wipe-sand-wipe method. Good tip!

[Jerry Woodward]

Originally Posted by Madehn

even simpler way-- use a piece of 1/2 inch G10--- drill and tap the holes for mounting bolts before mounting the pump-- epoxy the G10 in place using thickened epoxy OR use 5200 but the 5200 will need to set up for several days at a decent temp to reach full hardness-- drilling and tapping the G10 is super easy-- i just did 14 backer plates for thru hull installation on my boat in about 35 minutes with 5 or 6 bolts on each plate- the 5200 should be plenty strong to use and might be easier than epoxy-- when mounting the plate screw the bolts in without the pump until they are just below the surface of you are gluing-- if you want you can use a couple of dab spots of 60 second epoxy to hold the board in place while the rest of epoxy or 5200 dry. easy and professional looking and easy to take pump on and off if needed

Thanks everyone for great suggestions. I am not enthusiastic about bolts sticking down. That is already the current situation. I didn't elaborate, but I am replacing an original holding tank manual pump that no longer works with a larger one. There are 4 studs that were glassed in to a reinforced section of the underside of the deck. I had a heck of a time getting old pump out because the heads of the bolts broke free and the studs were free to turn, but not come out. The new pump has a different bolt hole pattern, so I need to remove the old studs. They are not coming out easily and I will probably have to cut them off, or try to dremel cut the glass around the heads.

So my original thought was to use 1" or so hex head lag screws and screw into 1/2" G10 appropriately drilled. Madehn suggestion to drill and tap the G10 and use bolts is also a good option. So now my question would be whether drilling and tapping G10 and using a bolt is better than drilling and using a slightly larger lag screw?

[Manateeman]

Plexus.