1981 Oday 28. Backer boards to all through-hulls were dry rotted. For a variety of reasons, I am replacing the through hulls and seacocks too. I was going to use marine plywood, but none is to be found for miles around. Thought about using untreated plywood soaked in CopperTox (37% solution of copper) as a preservative, but have thought more about installing a backer board with a synthetic board (e.g. King Starboard). One...what experience has anyone had using synthetic backer boards for their through-hulls? Good, bad, wished they'd done it another way, etc? Two...if Starboard is a reasonable choice for building backer boards, why couldn't I just use a Walmart white synthetic kitchen cutting board? Advise and comments are invited. And thanks.
Build your own thru-hull backer plates?
- Thread starter flyhop
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You can make your backer blocks from any
durable and some what flexible material. My preference is Honduras Mahogany or white oak because as it gets wet it swells a bit and seals the interface. Others prefer a synthetic material for the opposite reason it is stabile and doesn't shrink when it dries or take up when it is wet. Both have a good record. Use what you can find.
durable and some what flexible material. My preference is Honduras Mahogany or white oak because as it gets wet it swells a bit and seals the interface. Others prefer a synthetic material for the opposite reason it is stabile and doesn't shrink when it dries or take up when it is wet. Both have a good record. Use what you can find.
you know, it might be nothing sticks to it
I thought about doing the same, then I read that nothing will stick to the synthetic board. I know that when you install the thur hull, you need some type of caulking to seal the hull, but it seems that you need to use an expensive glue to stick it to itself, and caulk won't adhere either. So, even thought I think it's a great idea, I would hate to be the one to speak from "experience" of what happens to this synthetic board when used below the waterline. I made up some fiberglass pieces that I used, (4 years ago) suggested by some of the yard workers, and used those. Might not be any better, but I hated rotten wood too. Let us know after a few years if you are successfull or a very disappionted "use to own a boat" person. Sorry, just a little bad humor. Guess we should not joke about such and maybe, we should just do what we know works. HUM. Anyway, I'm going on 4 years now and still have nightmares that there is water flowing into my boat. Then I get to her and she is high and dry. Good luck, keep us posted!
I thought about doing the same, then I read that nothing will stick to the synthetic board. I know that when you install the thur hull, you need some type of caulking to seal the hull, but it seems that you need to use an expensive glue to stick it to itself, and caulk won't adhere either. So, even thought I think it's a great idea, I would hate to be the one to speak from "experience" of what happens to this synthetic board when used below the waterline. I made up some fiberglass pieces that I used, (4 years ago) suggested by some of the yard workers, and used those. Might not be any better, but I hated rotten wood too. Let us know after a few years if you are successfull or a very disappionted "use to own a boat" person. Sorry, just a little bad humor. Guess we should not joke about such and maybe, we should just do what we know works. HUM. Anyway, I'm going on 4 years now and still have nightmares that there is water flowing into my boat. Then I get to her and she is high and dry. Good luck, keep us posted!
Plastic cutting board will work fine.
fibreglass panel cut from a damaged boat or left over from a repair job would be maybe the best. If you use plywood, use real marine plywood. There is none made in the US or Canada. Look for names like Bryunzeel, Maranti, or Okume. It should have lots of plys, all plys some kind of hardwood, and have no voids on the edges when you cut it. Preservative won't keep inferior plywood from coming apart. A few extra layers of glass and resin before you cut the hole is OK for backing. Make sure you use enough bedding compound under the through hull, and under the backing if you use separate backing.
fibreglass panel cut from a damaged boat or left over from a repair job would be maybe the best. If you use plywood, use real marine plywood. There is none made in the US or Canada. Look for names like Bryunzeel, Maranti, or Okume. It should have lots of plys, all plys some kind of hardwood, and have no voids on the edges when you cut it. Preservative won't keep inferior plywood from coming apart. A few extra layers of glass and resin before you cut the hole is OK for backing. Make sure you use enough bedding compound under the through hull, and under the backing if you use separate backing.
Don't think you need caulking on the inside!
David: I don't think you need to worry about caulking on the inside of the hull, the caulking is on the thru hull fitting on the outside. Technically these backers are used to screw the seacocks to. Much of the time boaters are using ball valves and not real seacocks.
David: I don't think you need to worry about caulking on the inside of the hull, the caulking is on the thru hull fitting on the outside. Technically these backers are used to screw the seacocks to. Much of the time boaters are using ball valves and not real seacocks.
I made my own
I made my own backing plates that are very ,very rigid. I made a board of 5/8 inch solid fiberglass by laminating it on a sheet of waxed glass and alternating cloth and woven roving. Starboard is far to slippery and flexible for my liking. It does not create a good bond with the sealants. Once I made my fiberglass board I then ground the hull area with a sander & 40 grit to rough the surface then glassed the " 6" hole saw holes" directly to the hull making them part of the hull.. See pictures of my install here: http://www.pbase.com/mainecruising/image/80568227 Here: http://www.pbase.com/mainecruising/image/80568229 And Here: http://www.pbase.com/mainecruising/image/80568230 Also McMaster-Carr sells pre made fiberglass boards and while not in-expensive they are far les than buying all the materials and doing it your self. I already ahd the materials so it was cheaper for me to use what I had on hand for this project. These panels are very high quality and available in 12 X 12 inch squares. With a 5 3/4 inch hole saw it's easy to get four backing plates out of these. There are two grades of fiberglass panel available from McMaster that would be suitable: #1 - Standard Polyester Fiberglass Panel I would normally choose polyester fiberglass sheet--an extremely strong, dense, and heavy material that works very well for backing plates. This is the greenish material that I have used before. There are many thicknesses, but normally you might choose 1/4" or 1/2" for a backing plate depending on hull thickness. For a newer O'Day I'd go with at least 1/2 inch.. A 12"x12" sheet of 1/2" FRP is McMaster part #8537K26 is ($28.24). This page number may change in the future, but the part number should remain constant. Here's the link: http://www.mcmaster.com/nav/enter.asp?pagenum=3479 #2 - Grade G-10 Garolite G-10 Garolite is a product made using fiberglass cloth and epoxy resin. Plain G-10 is a good choice for backing plates as well and is somewhat stronger than the polyester FRP panel. (The similar grade G-10/FR4 is a flame-retartant version of G-10.) The price of G-10 is double that of the polyester sheet, and I question whether there's any true reason to use G-10 for this sort of application. A 12"x12" sheet of 1/2" G-10 is McMaster part # 9910T41 is ($56.04) This page number may change in the future, but the part number should remain constant. Here's the link: http://www.mcmaster.com/nav/enter.asp?pagenum=3483
I made my own backing plates that are very ,very rigid. I made a board of 5/8 inch solid fiberglass by laminating it on a sheet of waxed glass and alternating cloth and woven roving. Starboard is far to slippery and flexible for my liking. It does not create a good bond with the sealants. Once I made my fiberglass board I then ground the hull area with a sander & 40 grit to rough the surface then glassed the " 6" hole saw holes" directly to the hull making them part of the hull.. See pictures of my install here: http://www.pbase.com/mainecruising/image/80568227 Here: http://www.pbase.com/mainecruising/image/80568229 And Here: http://www.pbase.com/mainecruising/image/80568230 Also McMaster-Carr sells pre made fiberglass boards and while not in-expensive they are far les than buying all the materials and doing it your self. I already ahd the materials so it was cheaper for me to use what I had on hand for this project. These panels are very high quality and available in 12 X 12 inch squares. With a 5 3/4 inch hole saw it's easy to get four backing plates out of these. There are two grades of fiberglass panel available from McMaster that would be suitable: #1 - Standard Polyester Fiberglass Panel I would normally choose polyester fiberglass sheet--an extremely strong, dense, and heavy material that works very well for backing plates. This is the greenish material that I have used before. There are many thicknesses, but normally you might choose 1/4" or 1/2" for a backing plate depending on hull thickness. For a newer O'Day I'd go with at least 1/2 inch.. A 12"x12" sheet of 1/2" FRP is McMaster part #8537K26 is ($28.24). This page number may change in the future, but the part number should remain constant. Here's the link: http://www.mcmaster.com/nav/enter.asp?pagenum=3479 #2 - Grade G-10 Garolite G-10 Garolite is a product made using fiberglass cloth and epoxy resin. Plain G-10 is a good choice for backing plates as well and is somewhat stronger than the polyester FRP panel. (The similar grade G-10/FR4 is a flame-retartant version of G-10.) The price of G-10 is double that of the polyester sheet, and I question whether there's any true reason to use G-10 for this sort of application. A 12"x12" sheet of 1/2" G-10 is McMaster part # 9910T41 is ($56.04) This page number may change in the future, but the part number should remain constant. Here's the link: http://www.mcmaster.com/nav/enter.asp?pagenum=3483
agree with wood
I would go with wood or marine grade plywood - even better. Sealant will not stick to some of the plastic composites and although you have a seal on the outside w/ the thru-hull...you probaly want double protection with the backing plate being sealed. Also you should keep water from the bilge from getting inside getting the thru-hull via the backing plate. Go with wood and seal it up with either paint, epoxy or resin.
I would go with wood or marine grade plywood - even better. Sealant will not stick to some of the plastic composites and although you have a seal on the outside w/ the thru-hull...you probaly want double protection with the backing plate being sealed. Also you should keep water from the bilge from getting inside getting the thru-hull via the backing plate. Go with wood and seal it up with either paint, epoxy or resin.
Plastic
If you have a plastic fabricator close you can buy scraps by the pound. The only difference between starboard and the regular polyethelene is the UV resistance. I used 3/4" for backing on my stanchions and the sole under the head since neither will see sunlight (hope!) You can mill out gasket areas around your thruhulls, won't stick to the plastic but it won't go anywhere.
If you have a plastic fabricator close you can buy scraps by the pound. The only difference between starboard and the regular polyethelene is the UV resistance. I used 3/4" for backing on my stanchions and the sole under the head since neither will see sunlight (hope!) You can mill out gasket areas around your thruhulls, won't stick to the plastic but it won't go anywhere.
OK...so plastic's out...going with fiberglass shts
I appreciate all of the advise. Good suggestions, all. MaineSail...nice pics I did check out the McMaster-Carr catalog. I'm about 60 miles NW of their ATL store, so I'll call and see what they have in stock. For the inland freshwater sailing we do, this is probably overkill. But, you never know where you boat can take you. I have some other questions about the through-hull/seacock install, but will start a new thread. Again, thank you to all.
I appreciate all of the advise. Good suggestions, all. MaineSail...nice pics I did check out the McMaster-Carr catalog. I'm about 60 miles NW of their ATL store, so I'll call and see what they have in stock. For the inland freshwater sailing we do, this is probably overkill. But, you never know where you boat can take you. I have some other questions about the through-hull/seacock install, but will start a new thread. Again, thank you to all.
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