drilling kevlar

My kayak has a nice recess in the deck for a compass. To mount the compass, I need to drill 3/32" holes for #4 screws.

The boat is made of kevlar composite. Will a standard drill bit make reasonably nice, clean holes in this material, or should I be worried?


Normal bits, if sharp, should be fine.

if you get some fuzzing, you can do this step but it’s a bit extreme:

Drill the hole to your desired size, then drill it with a diameter 2x the size, fill in the hole with an epoxy-milled fibers mixture and let cure, then drill the hole the original size. That should seal off everything.

It’s a technique I recommend for wooden boats. But again, it’s taking it to the extreme.

Will this be just a through-hull hole with bolt and nut or will it be a pilot hole for a screw that will cut threads in the hole? If it’s the later, then you might want to consider finding a bolt and nut to use.

Drill lube
If you are sealing the hole stick with water or use rubbing alcohol it will evaporate and leave the surface clean for sealing. Sealing the holes will help prevent delamination.

Sharp drill at correct speed should stop this but a little fuzz may be a good thing. Just use a little epoxy resin on the hole and the screw threads, done right it may even reinforce the holes.

If its a light lay up hold a block of wood under the area you are drilling so you can apply some pressure to the drill without causing problems.

Be careful using coolants as it may stop a bond and allow moisture to get in to the layup.

Check how far the screws come through. I usually thread the hole then clip the point of. I always use a small piece of marine epoxy putty smoothed over the end of each screw. Stops the screw ripping dry bags, stops the screw pulling out, seals and reinforces the hole.

Backing up marine screws…
On thin layups, I like to sometimes back up the drill area by first epoxy’ing a small square of hobby plywood…1/4" marine plywood works fine…with 5 min epoxy. First, drill a tiny pilot hole in the boat to locate the exact position for the finished hole. Coat (waterproof) the piece of plywood with epoxy and cement it centered it under the hole, let cure. If it’s small enough, (1" square)you won’t need to clamp it. 10 minutes later, run a pilot hole through the wood, then slowly drill your full size hole. Coat the screw with epoxy or kicked off resin, and you’ll have a very strong attach point. Once in place, you can clip off the end of the screw and grind it flush. Use stainless hardware. It’s permanent…get it right the first time! :wink:

Before ya drill
put down a piece of maskin’ tape first over de area yer gon’na drill, mark yer hole on dat an’ then drill yer hole. Helps keeps de material from splinterin’. As already said, clean an’ seal de edges of de hole wit epoxy.


Just drill with a sharp! drill. Epoxy or other sealant in the screw holes and to cover any part of the screw that sticks through.

I use the screws that come with the compass, since these will be non-magnetic and marine rustproof.

Best of luck

You need a drill with a good RPM. Find a fast corded one. Usually the cordless drills are a bit slow on the RPMs.

I would put tape over both sides also, just in case.

As for a lubricant, I advise something strange, lard. Just put a dab on the drill. If it does get hot, it melts. When it cools off it wipes off easily.

The guys at Seaward gave me similar
advice as Fat Elmo said. They also said to start the hole by running the drill in reverse before actually drilling the hold. It helps keep the drill bit from walking.

They also had me use clear tape so I could easily see where to drill.

It worked perfectly on my Foster Shadow.

C’mon!! It’s KEVLAR!! I mean . . .if a bullet isn’t going through it there’s no WAY your drill will!

Reverse drill 'till you get through
the gelcoat, then forward the rest. Thats it.

No lubricant is necessary
The material is too thin to cause the bit to heat up enough to matter. If you want to use a lube, water is as good as anything when drilling composites. Actually, it’s better than anything oily, since it has no potential to cause any problems with the exposed fibers.

Delamination is not an issue…
…in compass holes as they not under any significant stress.

Just a sharp bit and this was done
hours ago before the thread started.

Oh Ohh
Ref. “C’mon!! It’s KEVLAR!! I mean . . .if a bullet isn’t going through it there’s no WAY your drill will!”

Warning; Kevlar boats may not protect you from balastics, be carefull where you paddle.

On the other hand sufficiently small calibre ordinance or large enough screws may avoid fuzzing and the need for drills. Anyone know the correct ramge to avoid the need to fix holes in the hull? Or the correct calibre to make the correct size hole?

for boats is not bullet proof. I believe it is Kevlar 49 and the bullet proof stuff is 29. Also kevlar in an epoxy substrate takes most of the properties away from it except the strength. It becomes easy to cut whereas in fabric form it is takes a special type of scissros.

Ummm, anyone have a problem with this suggestion??? Such as, ITS FLAMMABLE!!!

Don’t use rubbin’ alcohol
as a cleaner. It has additives dat might leave a residue. Use ‘denatured’ alcohol as a cleaner.

Fat Elmo

I use old, cheap office scissors, and
get excellent results. It’s all in the wrist.