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Boat Forum / Building / September 2004Putting a screw into fg with a anchor?
A few weeks ago I posted about fixing a seat on my sailboat that was loose. Today I removed all the screws and pulled the seat out. The screws are held only by the fiberglass; I thought there would be some wood, but there isn't. I plan on using bigger screws in the existing holes and adding a few new ones. My only real problem is what to do about one screw hole that I tried to fix last year, but just wound up making way too big for any screw. Can I stick a plastic wall anchor in it, or maybe a toggle bolt; or am I best off just abandoning it? Go to www.westsystem.com Pick 'Projects' then 'Index', then 'Boat repair & construction' then scroll down to 'repairing machined holes in fiberglass' and click on the link. Do what they say, and to thank them for providing such help, use their products. Jim > A few weeks ago I posted about fixing a seat on my sailboat that was loose. > Today I removed all the screws and pulled the seat out. [quoted text clipped - 6 lines] > a plastic wall anchor in it, or maybe a toggle bolt; or am I best off just > abandoning it? I have a "zone 2" hole, but unfortunately I have no access to the underside. However I do have a gallon of West epoxy and some fiberglass, so I think a couple more layers of glass to thicken what the screws go into is in order. Thanks. > Go to www.westsystem.com > [quoted text clipped - 16 lines] > > a plastic wall anchor in it, or maybe a toggle bolt; or am I best off just > > abandoning it? The simple rule is NEVER use screws in FG. They will always fail. Fastener load must be distributed with some kind of backing. Steve >A few weeks ago I posted about fixing a seat on my sailboat that was loose. > Today I removed all the screws and pulled the seat out. [quoted text clipped - 8 lines] > a plastic wall anchor in it, or maybe a toggle bolt; or am I best off just > abandoning it? > The simple rule is NEVER use screws in FG. They will always fail. Fastener > load must be distributed with some kind of backing. That would make good sense if it were possible. The boat was built with no backing, and there is no access to the inside now. Any suggestions? I could possibly move the thing the ropes from the jib go through out about 6 inches from the seat to the gunnels, where it can be bolted on. That would take stress off the seat, but would change the geometry of the jib somewhat. Would that make sense, or would it ruin the boat? John, I have seen this type of construction many times by FG boat manufactures. They practice this to save costs of course, knowing that the failure will occur after any warrantee period. The best repair is often a case of compromise and it differs from instance to instance. I am not where you are, so it is difficult for me to be precise, but your object is to fish a backing piece behind the glass inline with your fasteners. Consider cutting an access hole to slip an aluminum bar in behind. It should be no less than 1/4" thick, because you will drill and then tap holes for the new machine screws. The aluminum flat bar can be bent into a radius to facilitate slipping the bar through your access hole. You should drill and tap one 1/4-20 hole in the center of the bend. Approximate a mating hole in the remaining FG panel and drill that to .265" for screw clearance. Test that you can reach this tapped hole with a temporary, very long screw. Adjust the bar size or access hole if necessary. Don't be concerned about the access hole, because you have to repair the FG anyway. Apply 3M 5200 adhesive on to the aluminum flat bar and install as in the test. Align with the intended fastener line and wind up the temporary screw. This will flatten the bar and compress the adhesive to the back of the remaining FG. Repeat this as many times as necessary to back the entire length of the fastener line. Next, repair the access hole(s) with new FG and wait 72 hrs for the 5200 to set. The FG and aluminum has different expansion rates, so the adhesive must be strong, yet flexible. 3M 5200 is ideal for this application. Temporarily install the new seat and drill the new screw holes to the correct 1/4-20 tap size, #7, through the seat, FG and backing bar. Remove the seat and tap the new holes. You may consider doing this last step in increments, because of seat distortion under fastener load. You should use 316 stainless machine screws installed with Copper Ease or equivalent anti-seize paste. This will allow easy removal at a later date without concern of dissimilar metal corrosion. Do not forget to use large SS flat washers or a mating aluminum bar on the seat side, as the problem at the seat is the same. This will spread the seat load across the entire length of the seat and mating FG. Good Luck, Steve >> The simple rule is NEVER use screws in FG. They will always fail. >> Fastener [quoted text clipped - 11 lines] > somewhat. > Would that make sense, or would it ruin the boat? There is a SS toggle bolt available called "toggler" try that.......Never use a copper based antisieze on aluminum, it will self destruct.... Bill > John, > I have seen this type of construction many times by FG boat manufactures. [quoted text clipped - 46 lines] > > somewhat. > > Would that make sense, or would it ruin the boat? Actually, I used a plastic toggle bolt; had them in the basement the whole time.... It worked very well. I'll let you know next year how it holds up. I just read an article in Popular Science that said that mercury contamination will cause aluminum to disintigrate in a matter of hours by blocking the formation of aluminum oxide. Perhaps copper does something similar. |
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