wood screws in fiberglass?

[WDavidG]

I'm planning to add a second door on my closet to make the lower section more accessible for storage. I've purchased a matching door and hardware from Scamp. The screws that come with the hinges look like basic wood screws. I'm concerned that if I drill the same hole size I would use in wood the screw might crack the fiberglass since fiberglass doesn't give like wood. Am I just being too nervous? Will the threads cut into the fiberglass and hold as they do in wood? What is the best technique?

thanks for advice.

[Casita Greg]

Installing wood screws into fiberglass will chip the fiberglass around the hole and the fiberglass itself, due to the weight of the door, and being bounced around down the road, and will eventually cause additional fatigue in the glass at the mounting holes. I would suggest using machine screws with backing washers and nylock nuts. If you are intent on using wood screws, at least get screws that are long enough to penetrate a piece of wood installed behind the hinges to provide more of a purchase for the screws and to take some of the stress off the fiberglass. YMMV

[Donna D.]

My suggestion would be to check out how the other doors are mounted. Is there anything on the back side to hold the fasteners? Then do that exact same thing with the new door.

[BarbinBC]

Working on my closet last year I did the same as Casita Greg recommends with the addition of cup washers under the screw heads to spread the load even more.

[Raz]

As Greg suggests, any type of spiral will cause the gel coat to separate from the fiberglass. Even drilling holes can be a problem. Also without backing there's not much to hold wood or sheet metal screws. I prefer machine screws to a wood backing. I've used standard nuts with flat and lock washers but nyloks might take the vibration better. To drill holes I use a brad point bit but a twist drill run backwards also works. Raz

[Borrego Dave]

Originally Posted by Raz

As Greg suggests, any type of spiral will cause the gel coat to separate from the fiberglass. Even drilling holes can be a problem? Also without backing there's not much to hold wood or sheet metal screws. I prefer machine screws to a wood backing. I've used standard nuts with flat and lock washers but nyloks might take the vibration better. To drill holes I use a brad point bit but a twist drill run backwards also works. Raz

Interesting Raz, I've never tried a brad point, always used a twist with masking tape if I was worried about chipping the gel coat. Might have been lucky if it did chip as whatever went over it covered it up. I also agree that a wood backing is needed if you're only going to use a screw.

[wire]

Originally Posted by WDavidG

I'm planning to add a second door on my closet to make the lower section more accessible for storage. I've purchased a matching door and hardware from Scamp. The screws that come with the hinges look like basic wood screws. I'm concerned that if I drill the same hole size I would use in wood the screw might crack the fiberglass since fiberglass doesn't give like wood. Am I just being too nervous? Will the threads cut into the fiberglass and hold as they do in wood? What is the best technique?

thanks for advice.

I'd use rivets or nut and bolt. I doubt that 1/8 of fiberglass is strong enough to hold screws.

[WDavidG]

Thanks all. You've confirmed my concerns. I'll go with one of these alternatives - just need to figure out which will offer an option for a head that most closely matches the finish of the hinge (the single advantage if the screws).

[redbarron55]

Drill a clearance hole for the screws in the fiberglass and a smaller pilot hole in the wood behind.
I installed all of the cabinets and bulkheads in my project this way.
I also used all screws and no pop rivets in the pproject, but I did use washers to sperad the load and I also fitted the bulkheads and glued them to the fiberglass.
The rear wood cabinets were screwed in by Scamp and I think this is how they install the deluxe cabinetry as well.
The rivets leaked, but there was no looseness or leaking where the old wood cabinets were installed.
If the parts you were supplied are fiberglass then I would bolt them in with clearance holes in both parts.
(clearance holes mean slightly bigger than the fastener shank.)

[Scamper Jim]

Before you get too far along with your door project, look at the screws that hold the support bracket for the upper kitchen cabinets to the top of the counter. In mine there are four wood screws holding it at the base. If there is anything that gets seriously pounded and stressed while traveling, it’s the screws in that bracket. Has anyone heard of it coming loose? In mine, they are about as snug now as the day they were put in 33 years ago.

I have more confidence in a wood screw in 1/8” to 1/4” of fiberglass than a screw in ¾” of pine. As Donna said, check what was used to hold the other closet hinges, and then do the same. On mine, they are just small wood screws screwed into the fiberglass.

Btw, if you use a power hand drill to drive the screws, be sure to put the clutch on a lower setting so that it slips if the hole is not large enough for the screw. Holes in fiberglass do not expand much to accept screws as wood does. If they are too small, the fiberglass will stop them and the screw will be twisted off in a heartbeat. Figuring out how to deal with that problem will give you some time to contemplate the meaning of life.

[Casita Greg]

Originally Posted by Scamper Jim

Before you get too far along with your door project, look at the screws that hold the support bracket for the upper kitchen cabinets to the top of the counter. In mine there are four wood screws holding it at the base. If there is anything that gets seriously pounded and stressed while traveling, it’s the screws in that bracket. Has anyone heard of it coming loose? In mine, they are about as snug now as the day they were put in 33 years ago.

I have more confidence in a wood screw in 1/8” to 1/4” of fiberglass than a screw in ¾” of pine. As Donna said, check what was used to hold the other closet hinges, and then do the same. On mine, they are just small wood screws screwed into the fiberglass.

Btw, if you use a power hand drill to drive the screws, be sure to put the clutch on a lower setting so that it slips if the hole is not large enough for the screw. Holes in fiberglass do not expand much to accept screws as wood does. If they are too small, the fiberglass will stop them and the screw will be twisted off in a heartbeat. Figuring out how to deal with that problem will give you some time to contemplate the meaning of life.

If they didn't provide some kind of backing or support for the hinges in your trailer to support the weight of those compartment and closet doors, (especially including the support for the mounting fasteners,) it sounds like a pretty poor and low budget way to do it. Just because you have been lucky so far with yours doesn't make it the optimal way any craftsman would want to install these hinges. It just means that the manufacturer got away with the bare minimum to get by. It certainly isn't the way it should be done. A little extra reinforcement is always better than no reinforcement, especially when dealing with fiberglass.

[Uplander]

Taking a bit from each suggestion and mixing in my own experience I'd do the following: first masking tape or painters tape on fiberglass...then drill hole for bolts...back bolts with wood to distribute the load and offer additional support.
Pre-drill holes through the backer wood...run bolts through hinge, through hole in fiberglass (tape removed prior to assembly), through wood backer board...use washer then nut...tighten and then apply lock tight to bolt and nut to prevent vibration when traveling from loosening the nut.
Note if you ever have to remove nut/bolt use nail polish remover to dissolve the lock tight adhesive.

That concludes my 2 cents worth.

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Happy Camping

[WDavidG]

Originally Posted by Donna D.

My suggestion would be to check out how the other doors are mounted. Is there anything on the back side to hold the fasteners? Then do that exact same thing with the new door.

Donna,
Turns out the upper door hinges are screwed directly into the fiberglass, but on closer inspection I discovered that Scamp molded an extra thick band of fiberglass along that edge of the closet to handle the weight of the door. Not having that condition at the location of my new door, I'll use a wood backing piece as suggested by others.

Thanks all.