bgytr

Kirby 30?

did a quick calc for giggles. I estimated a structural section. With 2 supports 1/5th L in from the ends, the max deflection from self weight should be under 0.2 inches. Peak stress a bit over 700psi. If a 200 pound idiot sits on it at midspan, the deflection will be 0.62 inches and bending stress 3040 psi. (about weak axis) oh-- yield for 6061 Al is 40,000psi

ideal/theoretical- pin supports for uniformly loaded continuous beam with 2 supports, 1/5 of the total length in from the ends is where the moment will be minimized. real world- your mast is not uniformly loaded most likely with spreaders, rigging, etc. If you want more than 2 supports, you'll have a hard time getting everything level to get your desired minimized moment, so don't make a mountain out of a molehill. Just start with 2 supports about a fifth of the length in from the ends and add some intermediate supports to keep deflection down if that's what you want. Stress is likely not an issue, it's more deflection. As you add more intermediate supports, scootch the end supports more toward the ends til it looks good and you'll be fine. Shim the supports until they are all sharing some load- all done.

Can you close the tiller flanges at the aft end to make a continuous structure? Then slide it over the cassette and try to make it as tight a fit as possible, if needed put shims at the corners to make a snug fit. Then the loads get directly transferred into the composite much more spread out instead of a very concentrated bearing stress at the bolt.

Titanium is very bad in cyclic bearing.

Yes laws of thermodynamics.

I just ordered an epropulsion spirit 1.0 plus. Should be here in a couple weeks, intend on using in my 9ft avon inflatable tender for my sailboat. Will post how it works when I get it. Main thoughts was I didn't want gas cans on my sailboat, and usage would mainly be short trips back and forth to shore while anchored.

Why not a tyvek or similar suit with some gloves? The only foolproof way to keep that toxic crap off your body is to physically keep it off your body. It's simple, cheap, and safe. There's a reason the pros put that gear on- they don't want the hospital visits down the road.

I bought a Lewmar hatch to replace my fwd Atkins-Hoyle hatch. I was surprised how lightweight the base frame of the Lewmar was. Then found out Atkins-Hoyle refurbishes their old hatches so I sent the Lewmar back and refurbished the A-H hatch. The frame is a lot sturdier on the A-H and will likely go another 40+years.

Charts on the Bay are usually pretty accurate. There are some shifting shoal spots though and a few inaccuracies. 7' is pretty limiting for gunk-holing on the Bay. 4' or less is magic.

Any chance that CHESSS will adopt ORC or ORR-EZ? Lot better basis for ratings, and easy to implement.

bad idea cutting the mast like your rigger suggests. I'm a structural nav. arch. (going on 31 years). Don't do it. Figure out a new mast base to fit the mast or make a transition piece, or perhaps modify the deck fitting to accommodate the mast. The base of the mast can and will develop other strain/stress mechanisms. If you have vertical slots such as you describe, the mast base will want to spread due to poissons effect. This will induce a stress concentration at the top of the slot- estimate by a factor of 3 over the far-field stress. Any other purely non-axial load component (which is a certainty from mast flexing, vibration, stretch in the shrouds, etc.) will induce another level of uncertainty in stress direction which will likely be cyclical- meaning fatigue problems. Aluminum is notoriously bad in fatigue and I'd expect cracks to develop at the top of the proposed slot. Do whatever you can to keep the circumference of the mast intact at the base.

Making efficiency comparisons should be done by numbers, not emotions. Did you invest in Solyndra?

not in purchase price... still coulda used it as is, everything was functional.

I've already spent twice what I paid for it, and will likely spend that again in the next year, but it's worth the effort to me for this boat to restore it.