Best way to make 3" hole in fiberglass?

[ezaction]

I am about to put my first hole in my new 26M! I'm going to install a compass in the bulkhead that requires about a 3" to 3-1/2" hole. What's the best way to do that?

If it were wood I'd use a hole saw or possibly a jig saw. Would these work without chipping the fiberglass? Do I need special blades?

Any advice appreciated!

[Frank C]

It's supposed to help if you tape the gelcoat first with masking tape, but mine got chipped anyway. I used the hole saw to mount my tachometer on the pedestal. The flange of the instrument covers the lip, so light chipping of the gelcoat isn't visible. Anything larger than 4 inches requires jig saw or Roto-zip, both of which require a steadier hand.

P.S. I mounted my Compass on the port bulkhead, which is too close to the electrical panel in the X. Starting over, I'd mount it on the starboard bulkhead.

[ezaction]

Yes, I thought of that (interference with the electric panel.) I don't really want to relocate the electric panel so I guess I'll put it on the starboard bulkhead. I would prefer the port side though because starboard has 3 lines led aft and port only has one. They will prolly end up dangling over the compass.

[Bill at BOATS 4 SAIL]

Have you sailed your 26M yet? Your mainsheet line, going from your traveler to the boom will rub right against this area. Make sure your compass does not have something the mainsheet could get snagged on.

I would cut the hole with a sabre saw with a metal cutting blade. I put duct tape all over the area where the shoe of the saw would touch, and on the shoe of the saw, to help prevent scratches and chips. Drill a 1/4", or larger, starting hole to put the blade in.

[Jack O'Brien]

I recently bought a "10 Pc. Large Hole Saw Kit" at Harbor Freight Tools on sale for $3.89. It is item #36222 and cuts five diameters: 2.5, 3, 3.5, 4 & 5 inches. Comes in a plastic case. Needs a drill with 3/8" chuck.

http://www.harborfreight.com

[Chip Hindes]

It's difficult to make a perfectly round hole with a jigsaw; even with the tape it's hard to do it without damage. It's hard with a Dremel type rotary saw as well, although the damage is easier to avoid.

IMO, a hole saw is the only way to go. The hole is perfect every time and no taping is required.

[ezaction]

I just read the instructions; the compass actually requires a 4" hole (West Marine #383010).

Will go ahead and use the hole saw. Bill, I've only had about 10 minutes sailing with the dealer - not enough to notice any possible interference. I will take your suggestion and wait to sail her first! Would hate to have an extra 4" hole there...

[Rick Mathews]

Just thought I would mention an alternative to the 4" hole. When we purchased our boat our dealer, Blue Water of Seattle, mounted a Plastimo compass just to starboard of the companionway. It can be used as a hand bearing compass, so it slides into a bracket mounted on the boat by a couple of screws--no need to drill a large hole. We have been very happy with it. It is easy to read from the helm and can be removed to either take hand bearings or to store below out of the weather when the boat is not being used. Here is a link to it at West Marine.

Click Here

[Bill at BOATS 4 SAIL]

ezaction - Put your mast up. Attach the boom. Connect your mainsheet to the boom bail and the traveler, and swing it to the side your compass will be on. On the early 26M's, the mainsheet would rub right across this area. This may have already changed because an easy solution would be to move the bail slightly aft.

The compass I have used for years, and recommend, is very similar to the Plastimo used by Rick. It is the Silva compass, West model 195776. It also got a very good rating by Practical Sailor, several years earlier. I attach it to the top of the sliding hatch w/4 screws. It is on the boat centerline. It is front reading when sitting; top reading when standing. Can easily be removed by sliding it out of its bracket; to be used as a hand bearing compass to get a running fix, to be stowed below when not needed. It also works as a tell-tale compass; I keep it in a bracket above my berth at night. It floats.

[craiglaforce]

On my X, I installed a compass on top of the steering pedastal. I much prefer this location to the bulkhead. It i easy to sight over the compass while steering to see when to tack to clear points of land etc. Only a couple of small screw holes were required. Why cut a giant hole in your new boat if you don't have to?

[Bill at BOATS 4 SAIL]

Yes, "It is easy to sight over the compass while steering to see when to tack".
However, IMHO, when the compass is most needed is when you can't see, because of fog or darkness.
I've done long compass courses, at night, on boats with the compass mounted on the steering pedestal. I would get a kink in my kneck, looking down at the compass (which doesn't really give a good long-range perspective, in that location), and looking back up to see where I am trying to go.
One advantage the pedestal location does have, is it is on the centerline of the boat. If the compass is on the bulkhead, it is not on the centerline. If you go any distance, with the compass at a 10 degree angle +/- off the centerline, you will not be where you think you are. Those of you who have the compass bulkhead-mounted should try it sometime. You might be surprised.
Just my $0.04.

[Jim Bunnell]

Forgive a newbe question, but since you are on the topic of compasses - I'm outfitting a 26M with the ST4000mkII (thanks to whoever pointed out the sail price a few weeks ago) and my question is; since the autopilot has a fluxgate compass that displays on the control head, why do we need a magnetic compass as well? Is it just a safety factor (loss of power) or are there other reasons?

Thanks in advance.
Jim

[Dimitri-2000X-Tampa]

My magnetic liquid compass is on the port bulkhead and I haven't noticed any inteference from the electrical panel. Of course, I don't look at it much either...its just a backup to my waycool primary navigation system...that is, a Garmin 176C Chartplotter interfaced to an autopilot that drives the boat. On my previous sailboat, I didn't have a GPS and got caught in a thunderstorm or two where that old fashioned compass sure saved my butt. And it was mounted to the top of the helm which was a lot easier to deal with in that situation. I wouldn't have trusted the fluxgate as much although I suppose the more backups the merrier and electrical failures can happen at some bad times - maybe even during electrical storms when forward visibility can also drop to 10 feet or less from rain.

To reduce the possibility of gelcoat cracking when drilling, make sure to use a fairly new holesaw (not the old rusty one your dad gave you when you were a kid), also make sure the drill speed is high enough and that you always drill through the prettier side first (ie, more chipping happens on the backside). I suppose it also helps to do it in warmer weather.

[ezaction]

One advantage the pedestal location does have, is it is on the centerline of the boat. If the compass is on the bulkhead, it is not on the centerline. If you go any distance, with the compass at a 10 degree angle +/- off the centerline, you will not be where you think you are. Those of you who have the compass bulkhead-mounted should try it sometime. You might be surprised.
Just my $0.04.

Could you explain why it matters if the compass is off the centerline? It seems to me that you would get exactly the same reading at any parallel surface (for practical purposes, say within 20' of the center). Well, so close that any difference could not be detected by the human eye using a magnetic compass anyway.

Now granted you might be viewing the compass from a slightly different angle. Is this the difference? Unless you are sailing lots (hundreds?) of miles, I find it hard to believe it would make much difference. But then I don't have much experience in these things and I'm probably all wet.

[ezaction]

My magnetic liquid compass is on the port bulkhead and I haven't noticed any inteference from the electrical panel.

I was concerned with physical interference, not magnetic. The compass I have is fairly deep and wouldn't leave much room for a custom panel on the other side.