Baltic birch

[ron ll]

I have to make six 8” x 16” port light surrounds to stop water intrusion. The builder of this plywood and glass/epoxy cabin did a lot of things right, but the port lights are flush glass let into a rebate. This has resulted in a failure at the sharp edge of the rebate.

My proposed solution is to add this 1/4” frame which would be thoroughly bedded over the glass/wood joint and screwed on. (I originally planned these as bronze but that has turned outrageously expensive.) This picture shows a rough prototype that tells me the painted version looks fine, now I need to find the best 1/4” material. I can easily make a router pattern to make six of these and my current thought is to use 1/4” Baltic birch and epoxy the hell out of all sides and edges then paint it. So is Baltic birch a bad idea, even epoxied? Is there a better 1/4” material I should consider?

(Rough prototype)
3B152F12-0A27-468F-AE81-81C9DAA9B7B4.jpg

[Yeadon]

You can get 1/4" (3mm?) okoume from Crosscut or maybe even Builders Supply near the north end of the Ballard Bridge. I'd go for a true marine ply and not use the birch. BTW, I think Builders will even sell you a partial sheet. If when you go in through the front door, walk all the way to the right, there's a corner with partial sheets of marine plywood you can pick through.

[ron ll]

Good idea, thanks. I thought about making these from four pieces of sapele, but I figure that many corner joints is asking for trouble.

[willin woodworks]

Why would four epoxied corner joints on each one be more problematic than plywood that will be epoxied? I'd go with solid wood.

[ron ll]

Why would four epoxied corner joints on each one be more problematic than plywood that will be epoxied? I'd go with solid wood.

I just didn’t think flush corner joints in 1/4” material is practical, especially as there would be 24 of them.

[sp_clark]

Marine ply's fine for this but in a more rot-resistant species than okoume.

[ron ll]

Marine ply's fine for this but in a more rot-resistant species than okoume.

I agree now that Baltic birch isn’t the best idea, I had been working with it on some other projects and was impressed with how uniform and stable it is. But if not okoume, then what?

[sp_clark]

You can get 1/4" (3mm?)....

1/4" is closer to 6mm, 0.236" if we're being picky.

3mm's 0.118" or a whisker under 1/8".

[nrs5000]

Meranti would be better than okume. Cheaper too most likely.

[Yeadon]

1/4" is closer to 6mm, 0.236" if we're being picky.

3mm's 0.118" or a whisker under 1/8".

Of the ones I tend to buy ... there's the one that is about a third of the width of my thumb, another is about half the width, and then thick one is about the same width.

[sp_clark]

Take Yeadon's suggestion, touch base with Crosscut or BS near you, see what they might have in stock. Sapele'd be my choice if available; 8x16 out of 48x96 ought to yield at least 30 usable blanks, more if you're careful.

[ron ll]

Thanks Yeadon. Got a 48 x 48 1/4” meranti marine from Builders in the corner right where you said it would be. $50.

[jpatrick]

Ron, I was going to recommend the occume just because I think it mills better/cleaner than meranti. But, since you got the meranti, you can mitigate tear out by either climb cutting with your router, or using both top & bottom bearing flush trim bits. Routering the ovals means would be cutting against the grain half the time, this is the reason for caution.

Further caution: Don't climb cut if you don't know what that means or if you are uncomfortable with the process.

Jeff

[ron ll]

Thanks Jeff. Yup familiar with climb cuttting but also have nice double bearing compression bits so I think I’m good. Going to test cut a few on cheaper plywood to start.

[JimConlin]

I’d prefer sapele plywood.

[ron ll]

I’d prefer sapele plywood.

As these parts are going to be epoxied and painted, I think it comes down to the interior plys and the glue. I have a bunch of sapele 3/4” ply, but the sapele is only thin skin deep and I would suspect that would be true of 1/4” as well. Do we know which plywood has the best marine cores? Don’t know if the meranti marine is the best possible, but it was readily available. I think encapsulating it in epoxy will go a long way to protect it, and these will be screwed and bedded so easily replaceable (as long as I keep the router pattern.)

[John Meachen]

I've yet to see any birch plywood that conforms to BS1088 or equivalent.Bare birch ply will develop blue mould spots in a few weeks if left outside and the glue is of variable quality.For the intended use,the recommendation to use meranti or sapele is good and now some has been bought it will just be a case of cutting it to suit.From the description,I would cut a router template from 1/2" MDF or similar to give enough depth for the guide bearing of either a flush trimming bit or a radius cutter.For best effect it might need to be attached to a base which will help it to retain it's shape and maybe even have a cleat on the bottom for holding in a vice.

[Boatsbgood]

Heresy, but:
I have done similar, but with polycarbonate or acrylic sheet. Works, durable,easy to cut n shape, etc.
As I said, heresy.

[Yeadon]

Thanks Yeadon. Got a 48 x 48 1/4” meranti marine from Builders in the corner right where you said it would be. $50.

Excellent! Glad that worked out.

[ron ll]

Heresy, but:
I have done similar, but with polycarbonate or acrylic sheet. Works, durable,easy to cut n shape, etc.
As I said, heresy.

I seriously thought of that, but I really don’t like the static dust that clings to everything while working it. Plus it doesn’t paint well.

[WI-Tom]

I've yet to see any birch plywood that conforms to BS1088 or equivalent.Bare birch ply will develop blue mould spots in a few weeks if left outside and the glue is of variable quality.

I'm always intrigued that so many other experienced people have had such negative experiences with materials I've used without problems. Around here, non-marine Baltic birch plywood is readily available in home improvement stores. It's good stuff--5 equal (thick) plies in the 1/4" ply, and I've never found a void. The faces are quite nice as well. And at least on a trailer boat like mine, I've never seen any sign of any mould. The glue apparently holds up to immersion--my present boat only used Baltic birch for interior structure, but my first boat's hull was birch ply and it did fine.

I tend to take all the horror stories of "it'll rot as soon as you turn your back" (radiata pine) or "mould will appear in a few weeks" with a pillar of salt these days. (Does anyone actually try to use bare plywood anyway?) Perhaps the difference is that my boats live indoors on trailers, and are never on the water longer than a few weeks at a time?

Tom

[Don Z.]

ply and it did fine.

Perhaps the difference is that my boats live indoors on trailers, and are never on the water longer than a few weeks at a time?

Tom

Yes, exactly.

One more thing about baltic birch. Most of it is actually made in Russia. Not trying to start a political commentary on that, merely pointing out that embargos, etc. have driven up the price and availability has shifted. The Lumber Industry Podcast did a show on this, and the discussion also related to other types of ply that may replace it someday. We'll see how that goes. One thing the podcast speaks to is with plywood, you literally get what you pay for. I'm not talking remnants as discussed above, but the full size sheets. If you see a huge drop in price, there's usually a reason, and that reason usually relates to glue quantity or quality. YMMV.

[Chenier]

I think encapsulating it in epoxy will go a long way to protect it, and these will be screwed and bedded so easily replaceable (as long as I keep the router pattern.)

Don't forget to epoxy your screw holes before final installation. Those are routes for water penetration, too.

[StevenBauer]

According to my local hardwood supplier there is no more Baltic Birch available at the wholesale level. When the stock in retail stores is gone there won’t be any available for the foreseeable future. This store is sold out of all thicknesses except the 3/4. They have about 12 sheets of that left. I usually use 1/2” and 1/4” for drawer construction. Or used to.

[WI-Tom]

Interesting to hear that Baltic birch is kind of going away. Good thing I'm not building any new boats in the near future!

(Though I did like Baltic birch for the frames in my SOF boats as well).

Tom

[Chris-on-the-Boat]

Over the last 20 years i've seen BB work fine in cabinetry applications on the boat, but always eventually fails exterior. Our local supplier of 5x5' sheets has dried up.

For this application i would consider UMHW. Works as easily as wood and holds up for decades as bull rails and chafing gear on crab boats. Painted once a year you'll never know it's not wood.

Good luck!

[Gerarddm]

Tangentially, I might note that Baltic birch is not Baltic, it's Russian, and supplies have dried up due to their invasion of Ukraine and sanctions.

[wizbang 13]

From the beginning..I do not understand "failure at the sharp end of the rebate".
Water is getting in through cappilary action where the glass/epoxy meet? What is the glass bed in?
The purpose of these surrounds would be to push more bedding on top of the glass /wood seam?
Would you maybe better off figuring out how to make the initial thing not leak? Maybe make the bottom of the rebate slanted down? rebed with butyl rubber?
I think if it is capillary action drawing in water, a quarter inch of ply and goo on top of it all may not work.it might need a built in airspace to break the "suction".
just rain right? not getting pounded by waves or a hose?

[ron ll]

As nearly as I can tell, in the original build of this cabin over the old fish hold (1995 or so), the glass cloth was wrapped into the rebate over the square edge of the rebate. The cloth has started to fracture at this edge. It is not leaking into the interior space and it hasn’t caused any serious damage yet. But I see the potential for moisture to get between the glass cloth and the plywood. The port glass itself is bedded in probably 5200, and seems fine. I’ve also never really liked the appearance of that flush glass detail on an 80 year old boat.

[wizbang 13]

wait...yer fixin what ain't broke ?

[ron ll]

Over the last 20 years i've seen BB work fine in cabinetry applications on the boat, but always eventually fails exterior. Our local supplier of 5x5' sheets has dried up.

For this application i would consider UMHW. Works as easily as wood and holds up for decades as bull rails and chafing gear on crab boats. Painted once a year you'll never know it's not wood.

Good luck!

I made some other parts out of UMHW a while back. Yes it cuts and shapes easily, but I’m still cleaning the white plastic static cling dust from everything in my shop. Wonder if there’s a way to ground things and self to keep that from happening.

[ron ll]

wait...yer fixin what ain't broke ?

Nope. I can see it’s broke. Iffin’ I can see it’s broke, water can see it’s broke.

[sp_clark]

Wonder if there’s a way to ground things and self to keep that from happening.

I hate working with plastics for this very reason. Sometimes there's overwhelming reason to use them anyway but I regularly try to find alternatives whenever practical.

Worst offender seems to be acrylic & polystyrene, polycarbonate not so much. If you can manage to work out a way to ground literally everything the chips may migrate to, you may gain the upper hand.

Otherwise the only method I've found that offers some respite to the nuisance potential is a complete, effective and itself well-grounded vacuum dust collection system for the machines plastics are worked on.

[jpatrick]

Over the last 20 years i've seen BB work fine in cabinetry applications on the boat, but always eventually fails exterior. Our local supplier of 5x5' sheets has dried up.

For this application i would consider UMHW. Works as easily as wood and holds up for decades as bull rails and chafing gear on crab boats. Painted once a year you'll never know it's not wood.

Good luck!

Paint will actually stick to UHMW for more than a few days??????

Jeff

[sp_clark]

Paint will actually stick to UHMW for more than a few days?

Todd Bradshaw's reported many times that some plastics can be 'oxidized' at their surface by means of a propane torch that then will bond well to some epoxies. It may be possible that UHMW, treated in this fashion, would accept paint also.

This essay from 2003 mentions the process (scroll down to the paragraph on improving adhesion) so it may be worth some experimentation. Polypropylene and polyethylene (my knowledge of UHMW is limited to the latter) are both specifically mentioned as being materials effectively treated in this manner. Either ought to be appropriate for the OP's task if painting's possible.

Screen-printing on many plastics has been commonplace for decades but the type of plastic being printed demands careful choice of ink type for durability. It's also become possible since 2000 to use inkjet technology to print on many plastics but again the type of ink used (and the printers that use them) are specific to the type of plastic being printed upon.

If anyone reading this tries it, please report back on your results!