Coming soon: An addition to the Northeastern GIS herd.

[Alan Cohen]

So here's my build thread. I guess now I'll actually have to do it.

It's a little premature as I'm still working on my boat shed, AKA garage, to get it ready for power tool plug-ins and 4 season usability.

But here's my first step: an $80 CL trailer in better condition than it looks. Just needs some rust treatment, a few fasteners, new tires and a coat of Rustoleum:



If you look hard enough, you can see the boat perched there quite handsomely. I know I can.

Off tomorrow to see a man about some paulownia. My goal is to build this boat as economically as possible, both in pounds and dollars. Let's see what happens.

[scooterpontus]

The trailer looks perfect. Looking forward to see your GIS take shape


Goatislandskiffingothenburg.blogspot.com

[Sumbloak]

Sounds good. I'll be interested to see how light you can get it.

[Alan Cohen]

So I went on wood safari today. I visited a few specialty lumber yards and finally hit pay dirt in Lancaster PA, about 2-1/2 hours from home. I picked up 46 bdft of 8/4 paulownia for $5.25 / bdft and 22 bdft of really nice doug fir for $8.75 per (ouch).

FWIW the paulownia is 15.8# /cuft density, the fir is 33.5. Both were air drying in an open barn.



But the d.fir is very tight quarter grain:



so I guess it was worth it. I'll use this for the mast and spars. Maybe box, maybe birdsmouth, I haven't decided yet.

The paulonia is flat sawn and 2" thick. I will rip the frame members to the 3/4" dimension and end up with quartergrain there too.



I also picked up a slice of purple heart to maybe use as gunwhale and inwhale caps as well as a purfling accent strip somewhere.



If you're going to pay a slight weight penalty, it might as well be purple

[Sumbloak]

*wants to build it ultralight and ultracheap*

*buys a plank of purpleheart*



Not that I blame you. It's the sort of thing I'd be inclined to do myself. I once went to a timber show, determined to only buy something small and useful if I bought anything at all. Fell in love with a 10 foot by 18 inch by 1 inch plank of imbuia. Ahem.

[Alan Cohen]

The purple heart was $30 for a 3/4" x 10" x 6+' board. It called to me. It was actually cheaper per bdft than the fir. That stuff killed me. But I didn't want to skimp on spar wood.

I'm thinking about making oars from the extra paulownia and will use some PH strips in between the paddle laminations like pin stripes.

Back to the spars...I had a 2-1/2 hour drive back with nothing but my brain for company. So I started thinking about mast construction. What if I were to make compound strakes for either the birdsmouth or hollow box mast using a 1/2 dimension layer of paulownia and a 1/2 dimension of fir with some glass fabric in between. In other words instead of 1/2" thick fir, use a sandwich of 1/4" fir and 1/4" paulownia with a glass center. Once glued up, that would be one heck of a stiff mast.

[Beaton2]

Looks like nice stock! The fir price you got isn't bad. Did you buy the okoume yet? That hurts too. At least the cost is spread out over the life of the project so you can do it out of pocket rather than plunking down thousands all at once.

You might get some warping if you try to laminate the paulownia and fir in two layers. You'd probably have better luck doing it in three, maybe two equal thickness and thin layers of fir and one thicker paulownia in between or all three the same thickness. You could also then use quartered paulownia laminated strips for the core with a Doug fir strip on each edge so you don't see the paulownia when rounding over. I don't know strength wise..

[Alan Cohen]

There's another yard 1/2 hour north of me that has the Okoume - $78/sheet. Not bad. I'll pick that up next week.

I'll do some destructive testing on my spar ventures before I commit significant material to it.

[Sumbloak]

The purple heart was $30 for a 3/4" x 10" x 6+' board. It called to me. It was actually cheaper per bdft than the fir. That stuff killed me. But I didn't want to skimp on spar wood.

I'm thinking about making oars from the extra paulownia and will use some PH strips in between the paddle laminations like pin stripes.

The most effective place for it would be on the forward and aft faces of the oar shafts. It would make good engineering sense there.

Back to the spars...I had a 2-1/2 hour drive back with nothing but my brain for company. So I started thinking about mast construction. What if I were to make compound strakes for either the birdsmouth or hollow box mast using a 1/2 dimension layer of paulownia and a 1/2 dimension of fir with some glass fabric in between. In other words instead of 1/2" thick fir, use a sandwich of 1/4" fir and 1/4" paulownia with a glass center. Once glued up, that would be one heck of a stiff mast.

The glass would be useless and a waste of time. Otherwise yes, it would work, but would still require a slightly larger diameter for the same stiffness.

You might get some warping if you try to laminate the paulownia and fir in two layers. You'd probably have better luck doing it in three, maybe two equal thickness and thin layers of fir and one thicker paulownia in between or all three the same thickness. You could also then use quartered paulownia laminated strips for the core with a Doug fir strip on each edge so you don't see the paulownia when rounding over. I don't know strength wise..

Sounds too complicated for the possible benefits, if any. If the mast is sealed, warping shouldn't be an issue.

[davlafont]

Yeah, laminated mast sounds like overkill. But I can see where a composite of the two species could yield a light but strong mast. Maybe a box section with the two lateral faces in fir and the fore and aft faces paulownia? MIK has said the mast is over designed and could accommodate less than perfect lumber choices. If so, it might also accommodate some deliberate lightening.

Thanks for doing your own thread here Alan. Facebook is fun, but this sort of discussion would get chopped up over multiple threads and would never be a good journal of your experience.

Welcome aboard!



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[Beaton2]

The three layers with outer veneers and a quartered lumber core is the traditional practice for making laminated components. There is a good chance for warping when laminating two different species like fir and paulownia. This warping happens pretty quick and you may have difficulty working with the laminated boards to build the mast. I agree that the warping might be less of an issue once in the mast. I tend to think that sticking with one species is the way to go.

[Beaton2]

Here's an interesting video from Oregon State showing unbalanced construction. Warp happens in just a few hours.

https://media.oregonstate.edu/media/t/0_otc0lzsu

[Sumbloak]

Yeah, laminated mast sounds like overkill. But I can see where a composite of the two species could yield a light but strong mast. Maybe a box section with the two lateral faces in fir and the fore and aft faces paulownia? MIK has said the mast is over designed and could accommodate less than perfect lumber choices. If so, it might also accommodate some deliberate lightening.

Well the thing with an unstayed lug rig is that the faces all get loaded much the same at different points of sail. In structural terms there is no real difference between fore, aft, or lateral faces (at least as far as I can see). That implies a balanced laminate all round. For laminated to make sense you want the higher modulus species on the outer faces. Putting them on the inside is a waste in terms of strength (and stiffness) to weight.

If the mast is over-designed you could go for an all paulownia mast and see what happens. The safe bet would be to use birdsmouth oregon (Doug fir) with a 25% wall thickness. That would be the same weight as solid western red cedar, roughly the same breaking strength, and stiffer. That's probably the easiest way to go in terms of compromising between bonkers complicated and fairly light. If the (solid) mast is designed to handle less than optimal timber, my guess is that it would be fine with high grade WRC, so should be fine in birdsmouth oregon. Alan's oregon is as near to perfect as has ever come out of a tree. Check with Mik first, of course.

[Sumbloak]

Here's an interesting video from Oregon State showing unbalanced construction. Warp happens in just a few hours.

https://media.oregonstate.edu/media/t/0_otc0lzsu

Yeah that is interesting. I'm not sure it'd matter with mast staves though. Those are very flexible anyway before the thing is glued up, so some longitudinal curvature probably wouldn't be an issue. I think it would have to be extreme before it became a problem.

If in doubt, make a test strip with oregon/paulownia and see what happens. If it bends too much, make a second one and use it for gunwales, where that sort of curvature would make for easier fitting.

[Boatmik]

I'm all for lightening. But there is a risk involved.

I always say ... if you try something risky and pull it off with ease, then you end up being called a genius.

MIK