Bearer Material Selection

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jhuntley
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Bearer Material Selection

Post by jhuntley » Tue Aug 31, 2021 12:37 pm

First post for a while for me so hello again!

I have an approx 16' fiberglass hull that I would like to add some extra bearers in to for engine and boiler mounting. What material do people recommend for bearers? Also, should the bearers be totally encased in fiberglass or do you just fiberglass around the joint?

I've asked around various people and have received a different answer from everyone so I had may as well muddy the waters a bit further and ask on here! 😂
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RNoe
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Re: Bearer Material Selection

Post by RNoe » Tue Aug 31, 2021 5:27 pm

If the bearers are made from wood, then fully encasing them in fiberglass might cause water to become trapped, increasing the chances of wood rot.
The bearers in my wood hull are bolted from the bottom, with epoxy sealant (I think...) between the hull and bearers. Then painted to match the hull inside bottom.
Because I was not the person who installed them, I guess (during top drilling and threading) that the bearers probably are Oak.
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Re: Bearer Material Selection

Post by barts » Tue Aug 31, 2021 5:41 pm

The trick with getting wood/fiberglass joints to live in a boat long term is to keep the water away from the wood, since the wood will swell and change shape significantly when it gets wet and dries again. This will destroy the bond over time; see the large collection of rotting plywood/fiberglass all over the US boats as examples. This means that whatever wood is bonded to the hull needs to be totally enclosed in epoxy (and glass as needed). Since you'll probably want to change things over time (boiler, engine location, etc), you'll want to be able to drill holes w/o letting water into the wood. You can use metal angle bolted to the side of the bearers (w/ oversize holes in the bearers coated w/ epoxy). or devise some encapsulated barrel bolt scheme to allow bolting fresh wood on top of the epoxied bearers. And remember - polyester resin is useless for this work, use a good epoxy.

I'd do the following:

* Decide where the bearers are to run, and smooth the bottom where the bearers will rest w/ a angle head grinder + sanding pad.
* Make cardboard (or luan plywood) templates for the curve at the bottom of the boat. Note that port and starboard may not be identical.
* From nice 2" nominal wood stock, cut out both bearers; test fit and sand as needed. Drill holes as needed for angle or barrel bolts described above. I'd use fir in the PNW.
* Coat bearers (and the holes) w/ epoxy and let cure; it's easier now than when they're in the boat.
* Using thickened epoxy, glue bearers to hull; let cure.
* Create coved joints w/ thickened epoxy on all sides of both bearers; let cure. Sand smooth any drips or bumps.
* Using fiberglass tape and epoxy, bond bearers thoroughly to hull.
* Add renewable bearers.

There's lots of info out there on epoxy/glass/wood boat building. Again, keeping the water away from the wood is critical.

- Bart
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Re: Bearer Material Selection

Post by DetroiTug » Tue Aug 31, 2021 5:49 pm

Another Opine.

Just lagbolt to the hull about every four inches. Use marine bedding compound or Lifecaulk in between. Make them from white oak, Cypress or mahogany, then seal and paint with marine paint (porch paint). Sealing them with epoxy, once oil and water get in around the drilled holes, they'll deteriorate rapidly. Ask anyone that owned a speedboat with a leaking fiberglass floor, the wood goes in short order in the perfect cavity for mold. It's OK to get wood wet as long as has a chance to dry out. Oil wipes off.

Someone was on here a while back with encapsulated oil soaked bearers that became spongy and the fasteners wouldn't tighten if I remember correctly. Big job to fix it.

The older I get and the more use it with mixed results, the less of a fan I am of epoxy over wood, great for some things, but not always warranted.

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Re: Bearer Material Selection

Post by Lopez Mike » Wed Sep 01, 2021 1:54 am

Having just built the bearers for both my engine and boiler, I'll throw in my thoughts and experiences.

If you start with clean, and dry wood and seal it with both epoxy resin and cloth, there will be no significant penetration by moisture or oil. When it is necessary to bolt something to these structures, bed the fasteners in thickened epoxy or, as a second choice, 3M 5200. The best I've come up with so far are S.S. fasteners called Hanger bolts. They have a machine thread on one end and a wood thread on the other.

I just sold my 1971 Islander 36 which I acquired in 1986. The engine beds were falling apart. Poorly laminated and built with polyester resin. I removed all remnants right down to the fiberglass hull and built solid mahogany replacements bonded to the hull with thickened epoxy and then covered with cloth and resin. I attached 3/8" x 2" S.S. straps to the top of the mounts with S.S. flat head wood screws and attached the engine mounts to the straps with taped holes in the straps. Hanger bolts directly in to the beds would have been fine. That's what I'm doing on my launch.

33 years after this and after sailing all around the Pacific, they were still in great condition. Often wet and/or oily. No problems.

Wood and resin got a deservedly bad reputation due the the rather poor bond one gets with polyester resins. Great to build a hull. Not great to bond anything to anything.

I just discovered Black Locust. Native here in the N.W. U.S. at least and ignored by hardwood dealers. Incredibly rot resistant and easy to work with. People cut the trees down and burn them. Grab your chain saw and go looking.

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Re: Bearer Material Selection

Post by jhuntley » Sun Sep 05, 2021 9:48 pm

Thankyou for all the advice chaps, I've also had a few SBA members call me to give me advice so I think I've a plan of attack now.

I have a source of free, well seasoned oak which will influence my material choice! The sawing operation for this oak may be of interest to you lot:



(Not sure why the embedded video isn't showing so here is the link... https://www.youtube.com/watch?v=jXdjrs9TXGw)
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Re: Bearer Material Selection

Post by jhuntley » Mon Sep 06, 2021 9:52 am

Your thoughts on bearer position would also be appreciated please.

This is the hull I'm working with - she's approx 16' long. Photos are not ideal, they were taken from the sale listing.

Not sure of the state of the bearers/floor supports that are presently there so need to have a good dig about - if there is any doubt they will all be replaced. Do should I have a pair of longitudinal bearers along the length of the hull or just have them where I need to attach the boiler/engine, and then rely on the floor supports for extra strength?

I have no idea of the quantity of resin/glass I'm going to require either, any suggestions on how to estimate that?
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Re: Bearer Material Selection

Post by barts » Tue Sep 07, 2021 12:48 am

Not sure of the state of the bearers/floor supports that are presently there so need to have a good dig about - if there is any doubt they will all be replaced. Do should I have a pair of longitudinal bearers along the length of the hull or just have them where I need to attach the boiler/engine, and then rely on the floor supports for extra strength?

I have no idea of the quantity of resin/glass I'm going to require either, any suggestions on how to estimate that?
Since it's difficult to estimate exactly how weights are going to balance out, I'd use long enough bearers to allow you to adjust boiler and engine position to get the right balance - at least +/- 30 cm. The boat is small enough that your position will affect the trim significantly as well. You'll need floors anyway, so having those will make it sturdier.

As far as estimating quantities of epoxy: https://www.westsystem.com/estimating-c ... plication/

- Bart
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Re: Bearer Material Selection

Post by Lopez Mike » Sun Sep 12, 2021 5:54 pm

I second Bart's suggestion about making stuff modifiable. One medium sized passenger at one end or the other of the boat can negate all of your worrying about machinery locations. I've just gone through that on my new hull and finally just put it all in the middle and quit fussing over it. If I don't like it, I'll change it later. You'll get much more relaxed about this stuff as time goes on. Get it running for next season's steaming.

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Re: Bearer Material Selection

Post by jhuntley » Thu Sep 23, 2021 9:50 pm

Thankyou both for your responses - I think I need to stop overthinking things a bit and just get on and put it together!
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