I cannot find any thread that discusses this. How much space should there be between the thru hull hole and the thru hull? Tight, 1/8", 1/4"? Thanks in advance for any helpful answers.
Thru Hull space
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Just picked up a new through-hull last night and noticed that it specified 1/16" variation for the hole. I think it was 1-1/16" to 1-1/8". So, it needs to be close and tight. Better to cut too small and then open it up as needed than to cut too large.
Just picked up a new through-hull last night and noticed that it specified 1/16" variation for the hole. I think it was 1-1/16" to 1-1/8". So, it needs to be close and tight. Better to cut too small and then open it up as needed than to cut too large.
If the hole saw will slip over the threads of the thru hull
and you have the next smaller size that just won't quite fit inside the first hole saw then the second one is about right. Going too small can make for a real hassle. Cut some scrap first if you have any doubt.
and you have the next smaller size that just won't quite fit inside the first hole saw then the second one is about right. Going too small can make for a real hassle. Cut some scrap first if you have any doubt.
you need some space for sealant
Contrary to popular belief, 48Dodge got it right as you really do need sufficient space such that your sealant of choice can permeate the entire circumference. This becomes even more important if you are using an adhesive sealant so as to provide sufficient surface area on which it can bite. Making the hole too tight promotes the likelihood of a void space.
Contrary to popular belief, 48Dodge got it right as you really do need sufficient space such that your sealant of choice can permeate the entire circumference. This becomes even more important if you are using an adhesive sealant so as to provide sufficient surface area on which it can bite. Making the hole too tight promotes the likelihood of a void space.
Thanks again
I think the thing to consider is to drill the hole close to tolerance then use my Dremel and drum sand the hole to about 1/16 over to carry sealant. I plan to use BoatLife. I usually use 4200, but this time I'm trying Boat life. I NEVER use 5200.
I think the thing to consider is to drill the hole close to tolerance then use my Dremel and drum sand the hole to about 1/16 over to carry sealant. I plan to use BoatLife. I usually use 4200, but this time I'm trying Boat life. I NEVER use 5200.
Agreeing with Ross ...
from bad experience (but not on my boat) *o ! Don't make the mistake of starting with a hole that is too small with a hole saw or even a bit. Without a template that you can snug up to the hull or a drill press, it is a bitch to try to expand the hole once you already have one.
from bad experience (but not on my boat) *o ! Don't make the mistake of starting with a hole that is too small with a hole saw or even a bit. Without a template that you can snug up to the hull or a drill press, it is a bitch to try to expand the hole once you already have one.
Understood
I undersand the points, thank you. My intent is to be able to go just over thread tolerance so the fit is not dry.
I undersand the points, thank you. My intent is to be able to go just over thread tolerance so the fit is not dry.
I didn't mean
I didn't mean to purposely bore a hole too small. I meant to try to get the hole tight and if it needs to be opened up a little to get the through-hull in, it shouldn't be too much of an issue to open it up 1/16". If it's too small by 1/4", then it's going to be a pain to open up a hole evenly.
I didn't mean to purposely bore a hole too small. I meant to try to get the hole tight and if it needs to be opened up a little to get the through-hull in, it shouldn't be too much of an issue to open it up 1/16". If it's too small by 1/4", then it's going to be a pain to open up a hole evenly.
mainsail
I think you should re-read what I suggested. It sounds like you are saying the same thing, albeit differently. To restate, the hole should be only large enough so as to allow the thruhull and sealant to bond thoroughly with the hull. This isn't that complicated...
I think you should re-read what I suggested. It sounds like you are saying the same thing, albeit differently. To restate, the hole should be only large enough so as to allow the thruhull and sealant to bond thoroughly with the hull. This isn't that complicated...
Following ..
Following Ross' post about using a hole saw that will slide over the threads with.. Quote: "you need some space for sealant" and "Contrary to popular belief, 48Dodge got it right as you really do need sufficient space such that your sealant of choice can permeate the entire circumference" and "Making the hole too tight promotes the likelihood of a void space." Sorry Don, apparently I mis-read what you were saying and wanted to make sure Patriot did not use a hole saw that would slide over the threads...
Following Ross' post about using a hole saw that will slide over the threads with.. Quote: "you need some space for sealant" and "Contrary to popular belief, 48Dodge got it right as you really do need sufficient space such that your sealant of choice can permeate the entire circumference" and "Making the hole too tight promotes the likelihood of a void space." Sorry Don, apparently I mis-read what you were saying and wanted to make sure Patriot did not use a hole saw that would slide over the threads...
Clear
Gentlemen, This is what I love about fellow sailors. I asked a question, it got hashed out and now I know exactly what to do. Cheers and thank you.
Gentlemen, This is what I love about fellow sailors. I asked a question, it got hashed out and now I know exactly what to do. Cheers and thank you.
Squeeze or not
Last question I have. I've read it's best to caulk everything up and assemble the thru hull and just snug it up for a day then tighten it up in order to make a "gasket". Some others assemble it and tighten it right up and squeeze the caulking out of the mushroom seam. Opinions from you experts please.
Last question I have. I've read it's best to caulk everything up and assemble the thru hull and just snug it up for a day then tighten it up in order to make a "gasket". Some others assemble it and tighten it right up and squeeze the caulking out of the mushroom seam. Opinions from you experts please.
Chamfer the hole on the outside of the hull. Then when you tighten the fitting s
caulk will squeeze into the chamfer and form an O-ring the rest of the caulk just fills the voids between the hull and the mushroom head.
caulk will squeeze into the chamfer and form an O-ring the rest of the caulk just fills the voids between the hull and the mushroom head.
The 2 step tightening IS appropriate
for silicone which depends upon compression rather than adhesive qualities (it has little) for sealing. In that case the material is allowed to cure to form a gasket and then properly retorqued. This is NOT appropriate for adhesive based sealants for the reasons mainsail points out. That being said, I never use silicone onboard as I've always been able to find other materials that work better. You'd NEVER use silicone for through hulls.
for silicone which depends upon compression rather than adhesive qualities (it has little) for sealing. In that case the material is allowed to cure to form a gasket and then properly retorqued. This is NOT appropriate for adhesive based sealants for the reasons mainsail points out. That being said, I never use silicone onboard as I've always been able to find other materials that work better. You'd NEVER use silicone for through hulls.
Rick..
It really depends on what you call "adhesive based". A look at actual data numbers from 3M clearly shows that 3M Marine silicone is actually quite adhesive.. In reality, silicone has about 220 PSI of adhesion to a clean substrate. In contrast, 3M 4200 (polyurethane) has 300 PSI and Sikaflex 291, also a one part polyurethane, has an adhesion of about 221 PSI or only a one PSI difference from 3M Marine Silicone. Life Caulk and 3M 101, both single part polysulfides, have about 140 PSI to 170 PSI of adhesion which is considerably less than 3M Marine Silicone.. Silicone offers the least "elongation at break" of any of the marine sealants though. This means the more bedding the further an item can flex or move before breaking the seal. The clincher is that mechanical fittings should not flex or move much, if any, from the substrate to which they are bolted so this actually makes the silicone elongation at break number basically useless if you beveled or countersunk the hole. Even when I use silicone, which like you is almost NEVER, I still bevel the hole slightly and that compensates more than enough to overcome silicones rather weak elongation at break characteristics.. P.S. There is no silicone that I have seen or found that is bellow waterline rated not even 3M's..
It really depends on what you call "adhesive based". A look at actual data numbers from 3M clearly shows that 3M Marine silicone is actually quite adhesive.. In reality, silicone has about 220 PSI of adhesion to a clean substrate. In contrast, 3M 4200 (polyurethane) has 300 PSI and Sikaflex 291, also a one part polyurethane, has an adhesion of about 221 PSI or only a one PSI difference from 3M Marine Silicone. Life Caulk and 3M 101, both single part polysulfides, have about 140 PSI to 170 PSI of adhesion which is considerably less than 3M Marine Silicone.. Silicone offers the least "elongation at break" of any of the marine sealants though. This means the more bedding the further an item can flex or move before breaking the seal. The clincher is that mechanical fittings should not flex or move much, if any, from the substrate to which they are bolted so this actually makes the silicone elongation at break number basically useless if you beveled or countersunk the hole. Even when I use silicone, which like you is almost NEVER, I still bevel the hole slightly and that compensates more than enough to overcome silicones rather weak elongation at break characteristics.. P.S. There is no silicone that I have seen or found that is bellow waterline rated not even 3M's..
Progress
I used all the advice given. While my wife and were installing the Marelon fittings the damned thru-hull snapped in half. So...I'm back to bronze. Not downgrading Marelon, I actually think I got one of the few faulty thru-hulls with a pre-existing manufacturing cracks, but I'm not taking chances in a thru-hull on the bottom.
I used all the advice given. While my wife and were installing the Marelon fittings the damned thru-hull snapped in half. So...I'm back to bronze. Not downgrading Marelon, I actually think I got one of the few faulty thru-hulls with a pre-existing manufacturing cracks, but I'm not taking chances in a thru-hull on the bottom.
When considering elongation at break remember
that percentage elongation is figured on a very thin section. 1/16th of an inch is .062 inch and 200 percent elongation doesn't go very far under those circumstances. Usually the bedding is squeezed down to much less than that at some place.
that percentage elongation is figured on a very thin section. 1/16th of an inch is .062 inch and 200 percent elongation doesn't go very far under those circumstances. Usually the bedding is squeezed down to much less than that at some place.
Stretch
Even more reason for me to use bronze. I got mine installed today, perfect, got it snug, no stretch, no worries about it breaking.
Even more reason for me to use bronze. I got mine installed today, perfect, got it snug, no stretch, no worries about it breaking.
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