Drilling Fibreglass

[chriscorr]

I am about to drill a big (1") hole to site a new chartplotter at the front of the cockpit. Is there anything likely to surprise me as I drill through the fibreglass or will it behave much like a piece of wood? (I'll be using a drill bit and jigsaw blade designed for metal based on advice already received here...)

Thanks as always...

 

[Quandary]

For a clean 1" (or anything up to about 70mm.) hole I would recommend a hole cutter rather than a jigsaw. Tape the area of the hole to reduce gelcoat chipping. Go in from the gelcoat side, fast but accurately for the same reason, use a bit of ply backing if possible and don't apply to much pressure at breakthrough.

 

[sailorman]

use a hole saw with a fine cut

 

[davierobb]

hole cutter every time, superior finnish.

 

[Boat44]

In addition to the above, if you haven't cut grp before, the dust! Suggest you wear a mask/goggles (especially if the wind is blowing) and be prepaired to get the vacum cleaner etc. out afterwards.

It is easy though!

A

 

[fisherman]

I rate the flat blade type hole cutter.

 

[chriscorr]

Thanks for the advice so far... So helpful to have this forum! Screwfix catalogue suggests this for fibreglass...

http://www.screwfix.com/prods/10322/Drill-Bits/Holesaws/Grit-Edged-Holesaws/Grit-Edged-Holesaw-35mm

... but it's also the most expensive of all the holesaws they sell. Would anyone suggest a better type?

 

[boatmike]

Thanks for the advice so far... So helpful to have this forum! Screwfix catalogue suggests this for fibreglass...

http://www.screwfix.com/prods/10322/Drill-Bits/Holesaws/Grit-Edged-Holesaws/Grit-Edged-Holesaw-35mm

... but it's also the most expensive of all the holesaws they sell. Would anyone suggest a better type?

You can use a cheapie B&Q one but make sure it's sharp. To get a good size hole I usually cut a bit undersize and enlarge with a small flap wheel. This avoids chipping the gel-coat at the edges.

 

[earlybird]

The Screwfix product would be fine, really intended for lots of holes in fibreglass. If you need to buy the arbour as well, it works out rather pricey for a one-off. For myself, if I didn't have a hole saw. I'd chain drill about 4mm dia just inside the 1" line, break out the centre and finish off with a half round file. This might chip the gelcoat slightly if you're not careful with the file, but it's out of sight.

 

[saxonpirate]

Go for a hole saw every time. If you don't want to spend X on the real deal for a one off, buy a couple of cheapies. GRP is very abrasive so they'll probably be useless afterwards, but h/saws save time and are far neater. The chances are the layup in that area will not be very thick, so a couple of cheapies will do the trick. And you'll probably get through with the first one.

 

[alexrunic]

hole saw as mentioned previously especially as the hole is relatively small. if you are using a jig saw on fiberglass it's best to buy a proper blade they are sold for use on fiberglass and ceramic tiles and are coated with tungsten carbide and are about 5 quid. definitely use a mask and goggles and don't have exposed skin.

 

[PetiteFleur]

I've used a very cheap holesaw and it's worked fine, but useless for anything else as it gets totally blunted. The more expensive ones are better and last longer if you need to do more than one one hole.

 

[jimboooo]

hi , i am a joiner by profession , go for the hole saw everytime if you do need to cut the grp with a jigsaw use a fine blade , just make sure you drill it in the right place . mark once measure twice .

 

[maxi77]

Agree wholeheartedly with the holesaw route. I would not recomend the cheap ones with many spring steel saws fitted in groves in a backing plate but proper single size ones that fit on a mandrel with a pilot drill. I have built up a reasonable colection over the years. You can also make very neet holes by attacking from both sides if possible.

 

[snooks]

I got the screwfix bog standard plumbers kit, the hole cutters worked well on every hole that I've had to cut from the hull to internal bulkheads, the are also deep enough if you have to drill a hole at an angle

One thing to bear in mind is the size of your chuck...I was using a cordless drill and the chuck wasn't big enough to get the 13mm arbour in so I went to B&Q and bought a new corded drill for the boat for all of £20! It was the cheapest solution

ps 1 inch isn't a big hole....this is a big hole :

 

[Malish]

does the compass still point the right way with a chartplotter next to it?

 

[snooks]

does the compass still point the right way with a chartplotter next to it?

I have two bulkhead compasses, but surprising yes!

There's little/no difference between the two compasses, and the one right next to the chart plotter is as accurate as it was before I stuck the plotter a few inches away!

In the manual it says the plotter shouldn't be mounted within 1 metre of a compass, and if compass was slightly lower I was going to remove it and extend its hole to fit the plotter, but boats being boats I'd have had to cut out the top of my coachroof!!!

I was expecting the compass to spin or stick in one place, but to my surprise it all works fine

 

[Tranona]

Thanks for the advice so far... So helpful to have this forum! Screwfix catalogue suggests this for fibreglass...

http://www.screwfix.com/prods/10322/Drill-Bits/Holesaws/Grit-Edged-Holesaws/Grit-Edged-Holesaw-35mm

... but it's also the most expensive of all the holesaws they sell. Would anyone suggest a better type?

No, the standard ones from the same source (painted red) are perfectly adequate. Cutting just one hole will hardly wear the paint off! I have used these and no problems with chipping - just make sure you go in as square as possible. The one you are looking at would be for continuous industrial use.