Marine fir plywood would be a great material but I agree with Ernie that it was not likely marine originally. Pretty much all fir plywood in the last few decades has been made with waterproof glue. The difference with marine is that it has no voids.
Paul M
NS30U #211, Sandpiper
Cowichan Bay, B.C.
A number of places sell fir plywood they describe as marine grade. I don’t know if it really is Marine grade to standard BS1088.
Randy,
I had a boat repair/Fibreglass shop look at the gussets last year. They said they were sound and did not need replacing. They are one of the best shops in the area and I assume that they were giving good advice since they were passing up on money with that answer.
Mark Powers
I simply doubled up mine with plywood that I glassed before I sandwiched them with bolts and thickened epoxy then filleted them to the hull. I also installed larger metal rudder stops reaching to the base of the gusset.
Bob: I was just introduced to this stuff recently. I’ve a professional glass guy working on my boat and he’s using it. It seems like a great product. Cuts and sands easily.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Thanks, Joe – if it’s good enough for you, that gives me a lot of confidence in it.
– Bob
Solar Wind
Nonsuch 26C #143
Google is ok for finding Coosa, and if you look at youtube boatworkstoday you’ll see him using it. Mr. BoatworksToday knows his stuff; at least in my opinion - for what it’s worth!
John NS26C 046 Ottawa.
Here is a link to a Practical Sailor article about different core materials including Coosa, balsa and plywood.
https://www.practical-sailor.com/boat-maintenance/the-multipurpose-core
What is interesting is the article talks of the high compression strength of Coosa but it has less compression strength than end grain balsa or plywood. They suggest it would be good for transom but other articles suggest it should not be used for transoms because of it’s lack of compression strength. Also note there are different grades of Coosa. The article also says it is too stiff for curved surfaces. It is a matter of horses for courses.
Mark Powers
My guy just cut grooves to use in a rounded corner.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Ernie,
I’m considering whether or not to have my fore deck done for exactly the same reasons you cite. I did see a Youtube video where someone dug a piece of solid wood (possibly Philippine “mahogany”) out of the deck core. I’m considering whether that would be a good idea around the mast base and forward where the windlass sits. I have a chunk of teak that would work, and I can build that out rather than having the yard do it. Or is that too silly to contemplate?
b.
Brian
SV Serenity
Nonsuch Nereus #003
Pax River, MD
Solid core is usually plywood. Teak would be a bad choice as polyester resin bonds poorly to any wood and teak is particularly oily.
End grain balsa works because the resin can soak in and get a mechanical bond.
Paul M
NS30U #211, Sandpiper
Cowichan Bay, B.C.
The issues with solid wood go beyond the particular wood. There are actually some positives for plywood over solid wood sheets.
Quoting from Matweb.com, an on-line source on properties of different materials, “Plywood is made of several thin layers, or ‘plies’ that are laminated together. The layer structure leads to more uniform properties than solid wood, since the effects of grain anisotropy are minimized. The properties of plywood vary with the quality of the constituent layers…”
“Grain anisotropy,” is a fancy term for reactions to forces from different directions.
What this this adds up to is, if the plywood is of good enough quality, its resistance to forces acting on it is better than solid wood. Solid wood sheets, for example, can split along the grain if struck hard enough. Because the overlapping layers in quality plywood are oriented in different directions, the forces aren’t transmitted through the piece in the same way and the piece is less likely to split.
Modern glues have gotten to the point where high-performance aircraft are glued together rather than bolted or riveted. Several glues offer stronger-than-wood bonds; the piece will break where it’s NOT glued together rather than at the joint where the glue is. If the plywood is quality, the glue’s strong and water-resistant.
End grain balsa works in places where the forces acting on it can be assured to come mainly from a direction that works with the way its grain is aligned. That’s why it’s never used in high compression areas like where deck hardware will get bolted down hard. Where it’s appropriate to use, it’s effective and saves weight.
There are higher-tech coring materials which have all sorts of advantages (unfortunately, price NOT being one of them). If you want the absolute best and don’t mind spending money, they’re interesting to look into.
But, quality plywood remains a pretty good value from a cost/performance standpoint.
– Bob
Solar Wind
Nonsuch 26C #143
All good points but don’t waste money on marine plywood if you’re burying it in a deck. Any decent (no big voids) fir plywood will do fine. It’s main purpose is to resist the compression forces of fastenings.
I certainly agree that quality concerns are higher for structural elements, e.g., gussets. It’s all a question of tradeoffs. My own boat is a, let’s just call it, “eclectic” mix of high-end and low-end choices.
The lower quality materials you use, though, IMHO, the more care you should put into installation because deck leaks will cause bigger problems, faster.
Many alternatives work, but there’s no free ride. It’s just individual preferences about where and when you want to spend your time and your money.
– Bob
Solar Wind
Nonsuch 26C #143
Brian -
If you are going to re-do your foredeck, IMHO, have a very experienced marine fibreglass craftsperson do it. The area is the furthest thing from “flat”. The mast collar (the “partners”) sits on a formed surface that must be replicated such that the mast goes in and the collar is in the exact same location, in the exact same plane, that it was before the repair.
Furthermore, with all of this talk about core + plywood, etc., you need someone who can handle all of that neatly. As I mentioned, according to my buddy who did work at Hinterhoeller, fir ply was used. That is what came out of my drenched foredeck. And … that is what went back in (new and dry, of course) !!
Possibly, you are an old hand at fibreglass and this kind of work. If so, go to it. I sure would not.
Ernie A. in Toronto
Good point, Ernie. Having recently redone the eyebrow trim on my boat, I got a good education in what karma and compound curves have in common.
– Bob
Solar Wind
Nonsuch 26C #143
Randy,
I measured the location of the grease fitting on the rudder tube. On La Reina it is 3" from the top of the tube and appears to be centred between the gussets. Based on the measurements from Respite, it sounds like placement was not done to precise measurements.
Brian,
here is a link to an article by Don Casey regarding the princess of core material.
https://www.sailmagazine.com/diy/know-core-principles
MARK POWERS
I am absolutely not a fibreglass guy at all (but I am a woodworker!), so it will absolutely not be be doing the deck work around the masts. I have a piece of soft deck down the starboard side aft of a (probably poorly installed) deck prism, and that seems more my level of capability. Perhaps this autumn or next spring.
I am still waiting on the yard to give me an estimate on the deck, and they are generally amenable to me putting in some sweat equity. This was just a question to see if I could contribute in a non-standard way. Ah well, back to the drawing board. (I do have an update on the chain locker, if it will ever post…)
Brian
SV Serenity
Nonsuch Nereus #003
Pax River, MD
If you can access the wet area from under the deck it is often easier to go that route than tearing the deck up…
Brian, I have found that when I try to add photos the system will reject my posts as too long. Reducing the resolution of the photos will sometimes work.
Mark Powers
Mark,
I’ve noticed that when I hit the rightmost of the three buttons next to “Post message”, it puts the picture right into the post, but seems to have a size limit. When I use the “Paperclip” button (second from the right), that adds it as an attachment. People have to click on it to see it in a separate window, but much bigger files are allowed. Could that be what’s happening to you?
– Bob
Solar Wind
Nonsuch 26C#143