I am now ready to install air conditioning in my HUN 310, but when I talked with Hunter Marine about locating the overboard discharge, they told me that the hull is cored above the water line(with balsa wood!) and that I would have to clean out the wood and fill the gap with epoxy before installing the thru-hull fitting. This makes it a little more difficult and more time consuming that just drilling, caulking with 5200 and tightening the backing nut. I would appreciate any advise from anyone with first hand experience on above waterline thru-hulls in late 90s hunters. The boat is in the water so I was planning on tapping into the engine pickup temporarily until haul-out next fall but installing the discharge fitting while in the water. The factory also said that they normally make a small square with solid fiberglass for future A/C installation, but I could not identify such are when looking under the gully cabinets where the factory plan shows the discharge. HELP... *bzz Thanks, s/v Calaloo
Thru-Hulls Above the Waterline-All Sailors
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Well, you have to do it...
If you don't you run the risk of letting water get into the core, which would then rot. It's bad. This job sounds like a big deal, but it's a routine part of boat maintenence, you might as well learn it now. You'll use exactly the same technique when you add a deck fitting. Any book about fiberglass repair will show the technique. It's better if you have pictures to look at, so find Don Casey's book or fiberglass repair, or Charles Hinckley's--yes, that Hinckley--excellent book on general yacht care. Probably the West System manual has a picture, too, I can't remember. Basically, you drill through the hull with a hole saw. Inspect the core to see if you accidentally hit that solid fiberglass spot. Just kidding. You'll completely remove the balsa about 1/2 inch or so from the edge of the hole, then fill in the void with epoxy resin, thickened with colloidal silica to the consistency of peanut butter. Smooth and let cure. That seals in the wood, and you can proceed with your through hull installation. All of these materials are right in your nearby West Marine, so don't sweat it. I think all modern boat hulls are cored above the waterline. It's a good thing.
If you don't you run the risk of letting water get into the core, which would then rot. It's bad. This job sounds like a big deal, but it's a routine part of boat maintenence, you might as well learn it now. You'll use exactly the same technique when you add a deck fitting. Any book about fiberglass repair will show the technique. It's better if you have pictures to look at, so find Don Casey's book or fiberglass repair, or Charles Hinckley's--yes, that Hinckley--excellent book on general yacht care. Probably the West System manual has a picture, too, I can't remember. Basically, you drill through the hull with a hole saw. Inspect the core to see if you accidentally hit that solid fiberglass spot. Just kidding. You'll completely remove the balsa about 1/2 inch or so from the edge of the hole, then fill in the void with epoxy resin, thickened with colloidal silica to the consistency of peanut butter. Smooth and let cure. That seals in the wood, and you can proceed with your through hull installation. All of these materials are right in your nearby West Marine, so don't sweat it. I think all modern boat hulls are cored above the waterline. It's a good thing.
R
Rob
I Agree
I agree with paul on that one. You don't want to mess with water getting into your hull-core. For the time being (this season) - just tap off an existing thru-hull and see how it works.
I agree with paul on that one. You don't want to mess with water getting into your hull-core. For the time being (this season) - just tap off an existing thru-hull and see how it works.
Thanks Paul for the good advise,
but how do I make sure that I don't remove too much? I'm worried that I'll end up with a 4" hole and not be able to mend the epoxy with the hull. Do I need to use cloth between epoxy layers or just thickened epoxy without reinforcement. Thanks, s/v calaloo
but how do I make sure that I don't remove too much? I'm worried that I'll end up with a 4" hole and not be able to mend the epoxy with the hull. Do I need to use cloth between epoxy layers or just thickened epoxy without reinforcement. Thanks, s/v calaloo
Don't sweat it
You reall can't remove that much, it's hard to dig it out very deep. Some people say to put a 90 degree bend in a nail, 1/2" or so from the end, put it in a drill, and root out the balsa with that. I think that's a good way to scratch up your boat myself, but try to imagine the effect and do the same with a slower hand tool. You're going to drill a hole with a diameter to fit the hardware exactly. If you aren't visualizing this, please get a book and look at the illustration. No cloth is needed. The epoxy will bond to the fiberglass and be stronger than the material you removed. The only thing to make extra sure about is that you get the epoxy stiff enough (with the filler) so it won't run out, get on your gelcoat, your floor, you, etc. The first time you drill a big hole in your boat is an experience to remember!
You reall can't remove that much, it's hard to dig it out very deep. Some people say to put a 90 degree bend in a nail, 1/2" or so from the end, put it in a drill, and root out the balsa with that. I think that's a good way to scratch up your boat myself, but try to imagine the effect and do the same with a slower hand tool. You're going to drill a hole with a diameter to fit the hardware exactly. If you aren't visualizing this, please get a book and look at the illustration. No cloth is needed. The epoxy will bond to the fiberglass and be stronger than the material you removed. The only thing to make extra sure about is that you get the epoxy stiff enough (with the filler) so it won't run out, get on your gelcoat, your floor, you, etc. The first time you drill a big hole in your boat is an experience to remember!
Installations on/thru' Cored Sandwich
The cored hull is a “sandwich”, with the fibreglass (inner & outer) skins representing the bread, and the balsa (whatever) core representing the meat. 1. Drill the hole (through everything) to match the outside diameter of the thru-hull fitting. As stated, a hole saw works well for larger holes, as does a forstner bit. 2. Gouge out the inner core (meat) between the skins, to a depth (diameter) of about 50% of the hole diameter. Ie: For an (approximate) 1-1/4" thru-hull hole (3/4" thru-hull), you’d want to gouge out the core to a depth of 5/16" all around, which would make the gouged area about 1- 7/8" in total diameter (1-1/4 + 5/16 + 5/16). 3. Infill gouged area (back to hole perimeter) with epoxy. 4. Bond Backing Plate over hole. 5. Install Seacock See WEST Systems Manual: http://www.westsystem.com/webpages/userinfo/manual/ and: http://www.groco.net/parts/data/IBV-FBV-TB.pdf PS: I'ts often suugested that you install a 90 deg. Elbow (pointing upward) immediately inside the Thru-Hull Tailpiece, if practical. This brings (at least) two benefits, and one minor drawback: 1. It facilitates the installation of an Anti-Siphon Loop in the discharge. 2. It reduces the Lever-Arm acting on the cantilevered assembly. 3. It (slightly) increases the back pressure (head) on the Cooling Water Pump. HTH, Gord
The cored hull is a “sandwich”, with the fibreglass (inner & outer) skins representing the bread, and the balsa (whatever) core representing the meat. 1. Drill the hole (through everything) to match the outside diameter of the thru-hull fitting. As stated, a hole saw works well for larger holes, as does a forstner bit. 2. Gouge out the inner core (meat) between the skins, to a depth (diameter) of about 50% of the hole diameter. Ie: For an (approximate) 1-1/4" thru-hull hole (3/4" thru-hull), you’d want to gouge out the core to a depth of 5/16" all around, which would make the gouged area about 1- 7/8" in total diameter (1-1/4 + 5/16 + 5/16). 3. Infill gouged area (back to hole perimeter) with epoxy. 4. Bond Backing Plate over hole. 5. Install Seacock See WEST Systems Manual: http://www.westsystem.com/webpages/userinfo/manual/ and: http://www.groco.net/parts/data/IBV-FBV-TB.pdf PS: I'ts often suugested that you install a 90 deg. Elbow (pointing upward) immediately inside the Thru-Hull Tailpiece, if practical. This brings (at least) two benefits, and one minor drawback: 1. It facilitates the installation of an Anti-Siphon Loop in the discharge. 2. It reduces the Lever-Arm acting on the cantilevered assembly. 3. It (slightly) increases the back pressure (head) on the Cooling Water Pump. HTH, Gord
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