Screw thread type to use for fiberglass

Leeway · Post by **Leeway** » Mon May 19, 2008 9:09 am

Hello,

I need to screw down a tiller rub rail in a place where I cannot use nuts and bolts. What is the best thread type to use when screwing into fiberglass? TMK, there is no wood structural support where I will be screwing into.

Thanks in advance.

Lee

EmergencyExit · Post by **EmergencyExit** » Mon May 19, 2008 11:07 am

I think I'd drill a small hole to be sure the area was hollow, and if so would consider a bead of sealant between the rail and the hull, and use pop rivets as the fasteners.

Leeway · Post by **Leeway** » Mon May 19, 2008 12:08 pm

That's a great idea, except I jumped the gun and bought some stainless flathead sheet metal screws.

I'll see if I have some rivets at home that are are long enough. I can always use the screws on something else.

EmergencyExit · Post by **EmergencyExit** » Mon May 19, 2008 12:28 pm

Wonder how thick the glass is there ? That was why I thought of rivets as oppsed to screws - if the glass is thick enough to have several wraps of thread biting at once, it would be fine, esp if you 3M it.

If the glass is thinner, you just wouldn't get much bite.

That is a nice looking man-o-war you've got. I

Leeway · Post by **Leeway** » Mon May 19, 2008 1:03 pm

Thanks EE. There is some spidering of the gel coat in areas, but overall I think it is in pretty good shape for the age and rough use.

I did remove some pop rivets from the middle of the area I am putting the rub rail in. They were holding on the old tiller stay that must have broken years ago. I want to come up with something better for doing that, but for now I am using a bungy cord.

I will check the thickness tonight. If it is similar to the scrap pieces I just took out when installing the deck plates in the cockpit then I can test on those.

I might go the rivet route anyway if I have the right size.

Banshi · Post by **Banshi** » Tue May 20, 2008 4:07 am

As long as the fiberglass is not paper thin and you use a good adhesive caulk I think in your situation the screws will do the job. I am going to guess that you can't use bolts because of a lack of access. A future project could be to add a access port similar to what we use on Sunfish to allow the interior of the hull to dry if necessary and to do modifications as well as creating some storage on older boats that do not have the storage compartment in the rear. Here is a link where you can see the ones i put in on mine. http://www.byershome.net/_Boat/Sunfish/sunfish3.htm Mind you these are a bit larger than most but at 6'4" I need the extra room to get my arms in and out of them. You can by these screw on ports most anywhere and they are water tight.

Banshi · Post by **Banshi** » Tue May 20, 2008 4:22 am

Just saw the other thread and see you already have some.

Leeway · Post by **Leeway** » Tue May 20, 2008 8:57 am

Yes, as you can see in the picture below, I have a deck plate near where I need to put the rub rail. However, there seams to be something in the way and it will be very difficult to hold the nuts to bolt in place.

I'm going to go the screw route. I think I have about a 3/16 inch thickness there.

The rub rail is going along that back edge of the cockpit.