Cutting holes in my deck

[chriscorr]

Apologies for asking such a first timer question... I need to put some instruments in at the front of the cockpit and I need to run various cables through the stern. Searching other posts it seems I can just drill holes / cut them with a jigsaw but i've read various articles about protecting the exposed cut surface? Is this necessary or do I just seal around the instrument/connector/cable gland with sikaflex?

Is there a good book on cutting holes, attaching items etc?

 

[paulrh]

hi,
How I have done it before is to cover the area with masking tape prior to cutting, mark the tape with the size hole you require and either use a hole cutter or for larger holes drill a small hole and then use a jig saw. not to forget to check what is laying behind what you are cutting out ie wires, pipes
hope this helps.
paul

 

[VicS]

I dont think there is any need to protect the cut edge. You will be sealing around anything outside any way.

 

[simonfraser]

drill a pilot hole first

 

[boatbuilder]

You only need to protect the core if it is composite, if it is monolithic (solid glass) then you are ok. Foam and balsa need to be hard edged to stop the water getting in.

 

[garvellachs]

If you are really going to cut through the "deck" then you need to seal it if there's a sandwich layer construction there, otherwise water may get between the layers and cause misery in time. If it's a single layer of grp there's no real problem as others say.

 

[oldsaltoz]

Sealing the cut edge refers to holes cut below the waterline.

Avagoodweekend......

 

[boatbuilder]

I seal all holes in composite hulls, under the water I go further and skinlink.

 

[chuzzlewit]

Masonry drills for GRP : they don't go blunt.

 

[TigaWave]

You do need to seal the edges above the waterline for foam or balsa core... here is a good descirption and photos that shows how.
cutting holes in balso/foam core grp

 

[savageseadog]

Cutting holes in my deck ............Increases ventilation?

 

[Adaero]

The above link is pretty good.
One easy trick I have found on balsa cores is to put a bolt in a drill and use the hex part to remove the core by about 4 to 5mm deep. The core is so soft the hex part of a bolt is fine. This way the balsa is removed easily and you have no chance of slipping and cutting the glass both sides as the tool you are using isn't sharp. The thread diameter of the bolt also stops you from going too deep.
Hope that helps

 

[Scotty_Tradewind]

I'm always concerned about the gel coat 'splintering' up and leaving a very poor edge to cuts.
I have used a fine toothed circular saw blade at medium speed with reasonable results, having taped the area on top of the proposed cut after having drilled the pilot hole for the mandrel bit to locate, which seems to help. Practice on a scrap of some material first perhaps?
After cutting, I would face up the cut edge with a resin or gel if it were my boat, wherever the place of the cut was.
If it's to be covered up by a fitting it doesn't have to be 'like a bought job' but better sealed as belt and braces and it doesn't take long and is cheap to do.

 

[alexrunic]

[ QUOTE ]
Masonry drills for GRP : they don't go blunt.

[/ QUOTE ]
i can't see them cutting GRP i ve not had a problem with normal HSS bits

 

[Scotty_Tradewind]

As an addendum to my last note, my favourite tool is an oscilating cutter..... a Fein multimaster...... see videos on the website :-
http://www.fein.de/fein-multimaster/uk/en/media/multimaster_video.php or a similar but cheaper Bosch.
I wont go on as I could praise the Fein for hours, but with a fine toothed blade it will do square holes very accurately. If you tape a straight edge along the proposed cut line and run the blade along it and it leaves a very smooth edge.