Weight (WAIT!!) games

[slowpoke]

The other day when I went up to Chad's house to pick up the build jig he gave me, we had a long discussion about our builds, and one of the things he mentioned was that if he had it to do over again, knowing that the rules could penalize someone who built their boat to come in way under the 800 pound limit, he would build a little heavier in the center of the boat; i.e., use heavier ply for the bulkheads, etc.
So the other day at work we had some extra 3/4 inch ply, and I thought, "Ya know Rocky, listen to chad, he knows what he's talking about." And in my head Chad said, "do it, you can skimp other places if you have to lose weight." So the plan now is to make frames 89 and 110 out of 3/4 inch ply, and possibly use 1/2 inch on frames 53 and 124.

So what does everyone think? Am I making it TOO heavy? Remember, I'm building the traditional Long Cabin version. Tell me when to stop, before I make TANK II !

[jray]

Rocky I made frame 89 out of 3/8 ply for more strength. After flipping her back over now that all the fairing and glass is done I'm happy I didn't add any more weight. I don't believe you will need extra.

Edit I think most all of the cabin boats are at or over the 800# mark. Not saying that someone with the skills and knowledge couldn't build lighter. I've watched Chad's build from the start and have been envious of both how he approached the build and the precision he used during the build. My boat is now where close when comparing construction techniques. I had a friend from Florida who builds large boats for a living give me some advice when we were visiting about the build and my concern that it was going to be to light. (Before working the bottom) he said the weight will be there don't add extra. He was correct! My skills and the way the build went I don't have worries about being light.

[Chad]

I made a LOT of lightweight choices, so I have lots of room to increase the strength of the core of the boat if I did it again. So sure, I'd use 1/2"+ plywood for the frames from 89 to 124, and the keel box.

3/4" ply? If it was nice stuff, 7 plies or more with minimal core voids, I'd use that for the long cabin's f110, f124 and the keel box. f89 is too far forward for that much weight in my opinion, except across the bottom as a mast step. I would also use 3/8 or even 1/2" ply for the hull bottom, if using the rest of my lightening methods. This will be more effective (and cheaper) than adding full carbon or glass interior skins.

[bendoo]

I used 3 x 1/4" in for both those bulkheads....long cabin and still am ok on weight. Under the mast I wanted at least 1/2" and the bulkhead forward of the keel is critical because if you ground, the keel will cantelever on the bottom of the boat and the top of the keel will kick forwrd into that bulkhead...I want my keel to blow up and not my bulkheads. I also added extra behind the keel on the bottom of the boat.
Just the way I did it and it worked ok as far as weight goes. (under 800 lbs)
The hard part is we'll know alot more after these boats have been sailing for 3-4 yrs!!
Best of luck!
bd

[Chad]

Just saw your edited post, Jon. Thanks for the nice words, but I think your build has been as clean and efficient as any.

[ryderp]

OK after reading this thread, I went out to the garage and unstiched 89, 110, and 124, and have doubled up these frames. I've been concerned all along that most the stresses in the boat are right in this area, so this makes sense to me. While I was at it, I went ahead and traced the hull-side curves into the new "doubles".

Thanks for the timely advice.

Phil

[slowpoke]

I agree Phil, this is an area I think should be thickened up. I want to use the 3/4" on frames 89 and 110. I actually think the weight forward might help that "nose up" look you see when the i550's are resting. And I'm remembering what Shazza and TTB said about keeping weight forward in all but heavy winds.

[Kevin]

Speaking as someone who hasn't weighed his boat and has no idea if he's over weight or not, I'd recommend you put extra material where you think it will bring real benefit.

I added thwarts (doubled the bottom portion below the bunks) on frames 110 and 124. I doubled the sides of my keel box. I tripled frame 89 between the stringers and across the top to support the compression post and disperse the loads. I doubled frame 214 and tripled for the rudder attachment and motor mount. I also added stringers in the aft part of the boat.

The keel box sounds like a great place for a piece of 3/4" ply (assuming cabinet grade stuff). In the long cabin, frame 110 is just the front of that keel box so again using that 3/4" you have sounds good. All of frame 124 in 3/4" seem excessive (but it's free right and a lot of 124 is air. As Chad knows, the center of inertia is aft of the keel so adding weight behind the keel is better than adding it forward of the keel. Using 3/4" as a thwart on frame 89 sounds ok too (not that much bigger than just going between the stringers).

I wouldn't worry about how the boat floats when it's not sailing. Sitting on it's lines with no one in it is not as important (although it would be nice if it did, that problem is too much buoyancy in the bow and that's a design flaw). The boat needs it's knuckle in the water when going upwind, especially in the light stuff and in chop (let the bow cut through the waves instead of slapping them). That means putting the fat guy up front even if he's the owner if you have to. Maybe teach someone else how to helm and trim the main/jib from the forward position. Me moving my 210 pounds forward 10" has a much bigger impact on sail trim then having 10 extra pounds of anything at frame 89 or 53. I'd rather have that weight close to the center of inertia.

That's just my $.02. Kevin.