Fiber glassing question

[kartsahd]

I have a Carolina Skiff boat that I want to attach a grab bar to the floor. It is about 36' high by 12". I do not want to drill holes into the deck to keep away from water intrusion and I do not think the floor is thick enough to hold. The grab bar has an aluminum base of about 3" by 14". I plan on getting a piece of oak or poplar about that size, putting some bolts through it, making a putty of cab o sil and maybe some mat and gluing the board down with that. Then fiber glassing a few sheets of glass over that. Then I have a nice solid base to bolt to. What I need to know is this a good plan? I looked into just using JB weld or 3m5200 but I do not think it can take the strain. Any ideas? Thanks

[Gjac]

To answer your questions directly, alodine or anodize can be used as a primer for Al. But you don't have to turn this into a science project. Very simply there are 2 types of bonds chemical bonds and mechanical bonds. Primers are need for chemical bonds, abrading the surface is what you need for mechanical bonds. Something like 80 grit sand paper is all you need to abrade the surface of the Al and the epoxy with bond to it. If you glass the Al base in as I described in a previous post the load applied to the handle will be reacted through the glass that has encapsulated the Al base and the bond line becomes secondary. Any marine store like West Marine will carry a good epoxy for what you want to do. When you glass in the base extend the plies over the base 4 ins or so and if you use 4-5 plies taper the edge by 1/2 in for each ply. This will minimize the peel loads at the edge of the glass overlay. Even if something does not go as planned you can always add 4 through bolts one in each corner and seal with the 5200, and you will have a nice solid base. Hope this helps. Good luck with your project.

[kartsahd]

OK this is driving me a little nuts! The whole issue is {what will bond aluminum to fiberglass}! The 3m website does not say 5200 will bond aluminum except (maybe) and not as well as wood or other materials, and only if I prime the "metal". It does not say what kind of metal or what to prime it with. Also I can not find out if epoxy
and or what kind of epoxy will be strong enough to create a good bond that is why I was looking at fiber glassing a base and using mechanical "bolts" and also 5200 on top of it all for some give due to vibration ext. then bolting it down. I just want the grab rail to become part of the boat and not come off. I am thinking I will first try something and bear with me. Drilling several holes in the base plate so the 5200 can ooze through. Then using like 8 screws to the deck for a mechanical bond. I am about to just get some 8' bolts and go through the whole dang hull! LOL

[Bumpyroad]

I think I would use stainless T nuts on the bottom of the board instead of having those bolts sticking up. would consider gluing the board down with 5200? before glassing it in.
bumpy

[Gjac]

Two points. If water gets into wood and it begins to soften and eventually rots the head of the bolts will spin. Not an immediate issue but long term. The second issue is the thicker the bond line the weaker the bond will be. If you don't think your hull is thick enough I would use multiple layers of glass cloth and epoxy to bring it up to the thickness you want and let it cure. Then just glass in your grab bar.

[kartsahd]

Tis is what I plan to do.

[valhalla360]

theoldwizard1 wrote:

Gjac wrote:
I would not be afraid of through bolts leaking if sealed with the 5200 or 4200 and would be the strongest solution.

Both will leak over time. They really are not meant for below the surface bonding.

Actually they both are rated for below the water line and frequently used for that purpose.

That said, a good epoxy fiberglass job will look better and be stronger. I would steer away from methods that incorporate wood.

[theoldwizard1]

Gjac wrote:
I would not be afraid of through bolts leaking if sealed with the 5200 or 4200 and would be the strongest solution.

Both will leak over time. They really are not meant for below the surface bonding.

[theoldwizard1]

If that is for a person to grab on to, the amount of force that is applied at 36" is greatly magnified at the base. How is the base constructed. If it does not have multiple gussets it will fail.

The strongest wood for the job is white oak. Much better than red oak or poplar.

Thickened epoxy works well for attaching the wood to the floor, but start by applying un-thickened epoxy to the bottom of your board. Wait until it starts to cure before attaching to the floor.

[QCMan]

Have you thought of glassing a board to the floor and attaching to that? Seems like the way a boat builder would do it.

[Gjac]

The simplest way if you are going to use FG it to abrade the area where the grab bar will attach, solvent wipe with acetone, and lay 3 to 4 layers of woven glass over the flange of grab bar over lapping 3-4 ins on the deck itself. An 8 harness satin weave is easier to form around the bar than a square weave. I would use an good epoxy resin with the FG cloth maintaining a 60-40% cloth to resin ratio. If you go with a wood board and an adhesive like 5200 the adhesive wont fail but the wood bond line may if you bang it or put enough load on it. If you bond the board flat to the floor the wood fibers are very weak in that direction. Think how easy it is to split wood in that direction. Cab o sil is good for thickening the resin and works well for making a filet but adds nothing for strength. I would not be afraid of through bolts leaking if sealed with the 5200 or 4200 and would be the strongest solution. I am guessing your hull is at least 1/4 in thick.

[prichardson]

For a grab bar, your plan is next best compared to thru bolting. I would not trust any adhesive in that application. Make sure the deck is squeaky clean before doing the glass work.

[Bumpyroad]

JoeH wrote:
You can certainly glass the board down.... but you might want to try 5200 first. That stuff is really strong .

x2
bumpy

[JoeH]

You can certainly glass the board down.... but you might want to try 5200 first. That stuff is really strong .