My thoughts are: When you drill a hole with a hole saw it’s going to be a little larger anyway. But I don’t see the need for clearance – you want a fairly tight, solid fit. Lots of “goop” (...a technical term!) doesn’t seal any better. The seal is one molecule wide between the hull and sealant and one molecule wide between the sealant and the through hull. The rest is just mess to clean up! The seal will be on the through hull flange (on the outside) and the washer on the inside. Therefore any extra sealant in a larger hole would be redundant.
(I hate silicone and I hate butyl! ☹) ...jut sayin’ 😊 sam :-) From: Thomas Delaney via CnC-List Sent: April 5, 2017 12:14 PM To: cnc-list@cnc-list.com Cc: Thomas Delaney Subject: Re: Stus-List Drilling a Hole in the Hull (Sam Salter) Sam, Actually, your question is something I would like to hear the list's thoughts on. I've read that you should drill the hole a size larger than the thruhull, but I have no idea if that is best practice or not. Should I be drilling the hole the same size as the thruhull, or should it be a little larger? Best, Tom --- Snow Goose C&C 35 Mk I City Island, NY ---------- Forwarded message ---------- From: Sam Salter <sam.c.sal...@gmail.com> To: cnc-list@cnc-list.com Cc: Bcc: Date: Wed, 05 Apr 2017 11:17:10 -0600 Subject: Re: Stus-List Drilling a Hole in the Hull Using tape and starting in reverse to drill a neat hole through gel coat is good advice. Depending on where you drill, you might get balsa core, especially above the waterline (not sure if the 35 has a cored hull) I don't think silicone has any place on a boat. I'd use Sikaflex. (I'm not keen on butyl either - my deck to hull joint is butyl and it drips everywhere!) Why a 1 1/4" hole for a 1 1/8" fitting? sam :-) C&C 26 Liquorice Ghost Lake Alberta
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