Mystery - What do I have

[cygtoad]

2 bottles of Goo Gone, a wire brush, two rolls of paper towels, and a scrapper.

Not perfect, but good enough to be able to sand it in next phase without fouling the sandpaper.

I also did a first stripping (Citistrip) of the port side gunwale. From old paint I can see where the seats must have been mounted. Anyone have any idea of the depth of the seats? I did a little research recently and I am considering using Iroko wood (African Teak) for the replacement wood for the seats and coamings. It is a quarter the price of teak and it seems I can get it in much wider board widths. Farmed teak is pretty stingy on width as the trees get harvested young. I know the original's were probably mahogany per the forum, but Iroko might be better option rot wise.

[GreenLake]

There are websites that list wood types by suitability for marine use. Forgot where I found those in the past but should be easy enough to find.

[tomodda]

Ahn, seats, so much fun! I was in much the same place you're finding yourself, back in 2018. Old DS1, rotted-out seats, what to do? I'm going to answer your questions as best possible and give you some thoughts/my experience. Warning: long post ahead!

Anyone have any idea of the depth of the seats?

I'm assuming her that you mean width, how wide across is the surface that you sit on. Realize that the early wood seat boats were all a bit different, nothing was standard except the hull shape. My 1960ish boat (#497) has seats that are 11.25 inches at the thwart, although as the hull curves the width changes, it's a bit over 10 inches at the transom bulkhead. The big point to note is that the side tank bulkhead (where you rest your back, at least if it was taller) itself curves to follow the line of the hull. So the "back" (actually outboard side) of the seat follows a curve, while the front (inboard side) is straight. Hence the differing widths. My older boat (#37, 1958) had 10.5" seats, curved both sides. For what it's worth, the depth (thickness of the seat) is exactly 1 inch across the board. Lumberyards must have invented the dread "nominal inch" (7/8"s actual) at a later date.

For myself, when I built new seats for my dearly departed #37, I said "10 1/2 inches is way too skinny for my fat ass" and built them 15.5" wide. How did I come up with that width? I sat on my dining room chair, scooted as far forward as still felt comfortable, tilted the chair back and forward and made sure I still felt good, then measured how much seat I was using, tailbone to where my thighs hit the chair. 15.5 inches! Your mileage may vary, but I built the new seat to be comfy for ME, the hell with everyone else . I also built the seat with the front/inboard edge following the curve of the rear/outboard edge, so it's 15.5 inches all the way, fore and aft. Again FWIW, it's a Nominal Inch thick, so 7/8s, but i built it in a tropical hardwood (more on that below), so I'm happy for the bit of weight savings. I did not build my seat from a single plank (way to expensive, and lots of waste due to curves), but from 3 nominal 6 inchers, 5.5 inch actual.

Another consideration is thwart width. The original is 8" on my boat, YMMV. It doesn't really matter, you need a thwart that is a bit wider than the bracket on your centerboard, and apparently those are all different for the early DS1's. Measure your own bracket. A more pertinent point is how long to make your thwart. On the newer DS1's (molded seat) they are very short, just from the inboard seat edge to the CB bracket. In our wooden seat boats, they need to go all the way from the side tank bulkhead to the CB. Makes sense, right? The bulkhead takes the load of the CB (on the lee side, from the thwart in compression).

So now we need some way to connect the inboard side of the seat to the aft side of the thwart. When I bought her, my old #37 had a nice steel plate that went underneath the seat and thwart to do that. It was shaped like a big fat "L" with the long side going underneath the seat. I drilled a few new holes into the plate and reused it, worked a treat. BUT... I had some initial fitting problems and quickly found out that the weak point is exactly where the inboard edge of seat meets the thwart. I sailed with that point totally unsupported for a while (thinking to myself that I just wouldn't put any weight there till I got around to fixing it) and it was a near disaster. My foot kept stepping there at just the wrong times! Anyway, lots of leverage there and you need to support it somehow. Steel plate (once properly fitted) worked for me, but you can come up with your own solution (post underneath?), just remember that you WILL step on that corner one day and it will have all your weight on a lever arm from the next attachment point..... You get the picture, you risk ripping the seat off. And the only time you'd put your foot right THERE is during an emergency maneuver, so that makes the risk even worse. Support that corner!

Last point before we move onto hardwoods, the Daysailer bylaws on boat measurement (Book 3), state:

5.5. For DS class yachts manufactured with wooden seats, the original seats may be replaced with wood or fiberglass provided the original seating areas and dimensions are maintained

I asked the Bob, the DS Measurement Boss if my new seat dimensions were class legal and he OK'ed it. See thread here (also has a photo of before/after):

viewtopic.php?f=11&t=6771&p=40916&hilit=seat+width#p40916

Basically, as long as you don't make your seats SMALLER than the original, then you're good! On to hardwoods...

I did a little research recently and I am considering using Iroko wood (African Teak) for the replacement wood for the seats and coamings.

Tropical hardwoods in general are great for boatbuilding, they're all good but with varying tradeoffs. They don't rot, at least not very fast. If you keep them oiled or varnished, you wont see any appreciable rot in your lifetime and your grandkids can inherit some extra boat-related chores (oiling or varnishing, take your pick!). That being said, downside of tropical hardwoods: Heavy, Hellish to work with (cut/shape), and Expensive. Bottom line up top, I use Cumaru, a reddish Brazilian hardwood, which I sourced from Advantage Lumber (online). More on why that wood and that seller further below

So, tradeoffs. Lets start with the basic cellular structure of wood - it's made up of cells with very thick, rigid cellwalls all lined up in long vertical rows and the long vertical rows lined up horizontally in rings. Basically a big bundle of straws, the cell walls all line up in what's known as the "Cellulose ExtraCellular Matrix." What sets Tropical hardwoods apart from regular hardwoods, such as oak? Two things - the Cellulose Matrix (the straws) are much denser - much thicker walls. And the walls are much more rigid (harder) because the tree picks up all the minerals it can from the earth and embeds it into the Cellulose Matrix. Chemically, Cellulose is a sugar, so imagine sprinkling rocks into a sugar cookie! The end result is a Matrix so heavy and hard that there's no space (at a molecular level) for rot fungi to grow. Fungus grows as it's own matrix of tiny little tendrils in all directions, but in a Tropical Hardwood, these tendrils can't squeeze into the Cellulose Matrix, and if they do, then they get chopped off by the "rocks in the sugar". Form follows function. OK, so I just got all the way to the molecular level of wood, what does this all mean for our tradeoffs?

For boatbuilding, we want Tropical Hardwoods because of the rot resistance. But the density/mineral content makes them very heavy per board foot. But their hardness also means we can use thinner pieces of lumber and also that we can use less supports (the wood will bridge larger distances without bending). So your overall seat structure isn't too much more than regular hardwood, I think my seats + thwart came in at 80 lbs. In relation to my bodyweight, that's nothing. However, the density and hardness also means that it's a b*tch to cut, remember you're cutting rocks! To give an idea, I built a 15x20 deck in Tigerwood (softer than Cumaru) and went through 3 circular saw blades, and that was cross-cuts only. Good luck cutting curves, such as I did for my seats. I used a plywood template and ran a 3hp router with a 1/2" double-edge flute bit. For the non-woodworker - that is some heavy duty, expensive equipment (which I borrowed from a friend). I had to cut the curves 1/4" at a time (multiple passes) and sure enough wound up buying my buddy a new flute bit ($20), since we wore the edges off his. So all this makes Trop Hardwood expensive - heavy to ship from forest to lumberyard, expensive/labor and tool-consuming to cut into planks, expensive to ship from lumberyard to your house, and then expensive to work into the final shape.

At this point, you night be thinking "Why don't I just use Honduran Mahogany (softest tropical hardwood) or oak?" Because it rots. That's why you're here building new seats (and reading me!) in the first place. As GL suggested, look up the page on rot resistance for boatbuilding, also look at the "Janka Hardness" of the woods you are comparing, harder = more rot resistant. But with all the tradeoffs.... Maybe you're better off just building new Oak seats every 5-10 years? Whatever works for YOU. Why did I make my choice of Cumaru from Advantage Lumber? It was the best balance of price/performance/workability for ME. I've worked with Advantage Lumber before (various house projects) and like their salespeople, very knowledgeable and they respect my relatively very small project needs (bigger sellers only respect big contractors). They already sell lots of Cumaru for decking, so the original sourcing, shipping, and tooling price is spread over many customers. That being said, the real expense was shipping from Advantage to me, they only ship via domestic carrier, aka 18-wheeler truck, one came to my house. The boards, when bundled together are enough to give a UPS driver a hernia, hence the commercial truck. For my seats, I paid as much for shipping as for the planks, and that's with Advantage's warehouse being in-state to me. Was $150ish for each, so $300 total, although I had some extra lumber for other projects in that shipment. Bottom line, call their sales folks, explain what they are up to. My local lumberyard for contractors (i.e. a REAL lumberyard, not the "Home Despot") said they could source the same wood for me, about the same total price as Advantage. But I'd have to haul it home in my Subaru, so nah. There were heaps of other considerations, bottom line is that real Tropical Hardwoods are great but you have to really think through every step of the way from sourcing to installation.

Ok, that was yet another long brain-dump, hope it was helpful. Feel free to hit me up with any questions.

P.S. Alternatives - Softwood seats (Pine), completely seal them (8 sides, plus any screwholes) in epoxy, maybe glass them too. Cedar seats, rebuild every 5 years. Marine Plywood seats brushed in epoxy. Etc. I considered all of these and decided that Cumaru was still the way to go (epoxy is expensive too!). YMMV, give it a think.

P.P.S. Look here if you want to read some extra whinging about how I made my seats, and an extra photo: viewtopic.php?f=1&t=5853&p=34427&hilit=seat+width#p34427

[cygtoad]

Thank you gentlemen. Lots to think about. I appreciate the measurements for the seats. I get what you are saying about the variable width, Tomodda.

I just started a new job so the attention I can give to the boat is going to be a little less than I would like, however, I have the whole winter to tackle the project.

I just bought the HEPA bag and filter set-up for my Rigid shop vacuum which I will hook up to my sanders. I read a nightmare story of this guy grinding away at his boat in his garage and the ventilation system sent fiberglass all through his house. Yikes!

Lucky for me I don't have forced hot air and the lower garage can be closed off while I am working. Still, I want to limit the amount of glass I get airborne. Planning one wearing a respirator too. I think I should be OK as long as I am careful. Safety first, right.

[GreenLake]

Definitely good to have an eye on safety. Even with this setup some dust will not get collected so plan on wearing a mask, of course. Good luck!