Fitting a new Tru Design through-hull between tides - sealant questions

Norman_E said:
I have 90 degree hosetails fitted with 5331, and its no problem at all. 5331 does allow you to adjust the position a bit even after curing for a few hours. Method of application is to put three axial beads of it at 120 degrees on the male threads. then screw the fittings together.
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Thanks for your further thought. As said, by my reading of the differing properties, the 5331 has the advantage on faster curing time and the 201i has the edge on strength of bond. So with the tide returning the 5331 looks best. Once the hull is watertight I can afford to wait so the 291i edges it.

(P.S. - not for Norman E, but to avoid misleading anyone else Loctite 5331 is not recommended by Tru Design for sealing through-hulls .)
 
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I agree, I would not use it to seal the through hull, that is a job for 291i, but 5331 is fine for all threaded fittings inside the hull. I put in my new Tru Design fittings in September 2014, replacing all the though hulls and ball valves, and they have proved a very good choice with all the ball valves moving freely and no leaks whatsover from any joints. All through hulls were sealed with 291i and all threaded pipe connections from through hulls to ball valves and ball valves to hose tails with 5331. There are three 38mm fitting sets, plus smaller sizes for engine coolant inlet and fridge cooling water inlet and outlet.
 
I would like to just add that re-tightening again the fitting after the sealant has cure may not be a very good idea. Common sense made me tighet all my fittings one time for good and let it cure like this. The thought that the sealant will be squeezed out is not correct because normally the flange of the fitting has a groove that serves for keeping more sealant there.
If the fitting doesnt have a groove you could chamfer slightly the hole so there should be a place for the sealant to make a thicker body. I am not sure polyurethane should be squeezed because its not a gasket making material as silicone. Maybe retightening could distract the polyurethane adhesion.
 
Akestor said:
I would like to just add that re-tightening again the fitting after the sealant has cure may not be a very good idea. Common sense made me tighet all my fittings one time for good and let it cure like this. The thought that the sealant will be squeezed out is not correct because normally the flange of the fitting has a groove that serves for keeping more sealant there.
If the fitting doesnt have a groove you could chamfer slightly the hole so there should be a place for the sealant to make a thicker body. I am not sure polyurethane should be squeezed because its not a gasket making material as silicone. Maybe retightening could distract the polyurethane adhesion.
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Tru Design recommend tightening to 'finger-tight' straight after application of Sikaflex 291i. With a big nut this is already pretty tight. Final tightening is to 15 ft/lbs (not super-tight) after 2 hours which is 1/12th of the time taken for full cure. So their recommended difference between the two tightenings is not that much and seems to make sense to avoid squeezing too much out by initial over-enthusiastic tightening. (Not that you are suggesting that.)
 
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Poey50 said:
Tru Design recommend tightening to 'finger-tight' straight after application of Sikaflex 291i. With a big nut this is already pretty tight. Final tightening is to 15 ft/lbs (not super-tight) after 2 hours which is 1/12th of the time taken for full cure. So their recommended difference between the two tightenings is not that much and seems to make sense to avoid squeezing too much out by initial over-enthusiastic tightening. (Not that you are suggesting that.)
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Ok then sounds like a plan.
Probably you already know those but i will mention them just in case thats your first hole through the hull: Make sure your pilot hole is excactly 90 degrees to the hull. I suggest you take a piece of 20 mm plywood and predrill a 90 degrees hole on it. Then set it flat on the hull and use it for setting your hand and drill at the correct angle.
When you start cutting with the hole saw, set it to counter clockwise, so you first make a groove on the jelcoat without braking it. Them set it to clockwise and give it light bursts of 3-4 seconds otherwise it could start generating temperature and start smoking. When you are almost at the end give the lightest pressure so you dont break the last internal layer of glass.
Lastly the internal surface should be totally flat. If for example there is a weep of old polyester it would disturb the flange sitting flat.
Good luck!
 
Tungsten carbide tipped holesaws like this https://www.ebay.co.uk/itm/13-100MM...m=113419288125&_trksid=p2047675.c100005.m1851 make light work of drilling fibreglass, and I have also used them for cutting holes to fit level gauges into stainless steel tanks. Available in 48 & 50mm sizes, but I have not seen 49mm.

With any holesaw I prefer to drill the pilot hole first, ensuring that it is square, then replace the drill in the holesaw with a plain piece of steel so that it cannot enlarge the pilot hole and allow the holesaw to work at an angle or cut oversize. I then cut at least half way from one side, and finish from the other.
 
Akestor said:
Ok then sounds like a plan.
Probably you already know those but i will mention them just in case thats your first hole through the hull: Make sure your pilot hole is excactly 90 degrees to the hull. I suggest you take a piece of 20 mm plywood and predrill a 90 degrees hole on it. Then set it flat on the hull and use it for setting your hand and drill at the correct angle.
When you start cutting with the hole saw, set it to counter clockwise, so you first make a groove on the jelcoat without braking it. Them set it to clockwise and give it light bursts of 3-4 seconds otherwise it could start generating temperature and start smoking. When you are almost at the end give the lightest pressure so you dont break the last internal layer of glass.
Lastly the internal surface should be totally flat. If for example there is a weep of old polyester it would disturb the flange sitting flat.
Good luck!
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Thanks for this. I was a bit surprised that Tru Design recommend drilling both pilot hole and the main hole from the inside of the hull but I assumed that perhaps this was to avoid tearing up the inner layer of glass (but at the risk of chipping the gelcoat). I can see that drilling the pilot hole from the inside gets over the problem of locating the exact spot from the outside. I have done one previous through-hull (a gas locker drain) but located the drilling point from outside by taping a powerful button magnet to the exact spot inside and then another magnet from outside to fix the spot. So I'll do that. Your advice on using a guide is a good one which I hadn't thought of.
 
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Norman_E said:
Tungsten carbide tipped holesaws like this https://www.ebay.co.uk/itm/13-100MM...m=113419288125&_trksid=p2047675.c100005.m1851 make light work of drilling fibreglass, and I have also used them for cutting holes to fit level gauges into stainless steel tanks. Available in 48 & 50mm sizes, but I have not seen 49mm.

With any holesaw I prefer to drill the pilot hole first, ensuring that it is square, then replace the drill in the holesaw with a plain piece of steel so that it cannot enlarge the pilot hole and allow the holesaw to work at an angle or cut oversize. I then cut at least half way from one side, and finish from the other.
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I have finally located a 49mm holesaw on eBay - but not cheap. I like your suggestions about replacing the bit with a guide and cutting from both sides and I'll do that.
 
Poey50 said:
Thanks for this. I was a bit surprised that Tru Design recommend drilling both pilot hole and the main hole from the inside of the hull but I assumed that perhaps this was to avoid tearing up the inner layer of glass (but at the risk of chipping the gelcoat). I can see that drilling the pilot hole from the inside gets over the problem of locating the exact spot from the outside. I have done one previous through-hull (a gas locker drain) but located the drilling point from outside by taping a powerful button magnet to the exact spot inside and then another magnet from outside to fix the spot. So I'll do that. Your advice on using a guide is a good one which I hadn't thought of.
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Magnets work great! i did the same thing for all the holes i drilled.
For a bi-metal 48mm i paid around 6 or 7 euros. The 1 1/2 fitting got in precisely without any play left-right.
 
This sounds like a worthwhile project. Has anyone any info about how long these have been on the market and their expected life please.
 
Norman_E said:
I think that Tru Design suggest sealing the ball valve to the through hull with PTFE tape. I found that the threads are a pretty loose fit and would have needed a lot of tape.
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Agreed but when I popped into Screwfix I found they do a bag of much thicker PFTE rolls for about £5. Its the thickness of card so only needed a few raps to seal my Trudesign.
 
Poey50 said:
Thank you. ........

One issue that I can't quite get my head around is how to ensure that the handle of the ball valve is the correct orientation when using a load bearing collar since, with the through-hull fixed, the height of the collar determines how much the ball valve can be tightened down. Probably the base of the valve doesn't have to be a totally snug fit against the collar as the valve is held by the sealant.

Thanks, by the way, to all who have offered suggestions - very helpful.
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I cant remember what I used on the thread between skin fitting and valve, but I did use a back nut to help holding the valve in the correct orientation.
 
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