35' cat concept for the inside passage.

no worries, that looks like a really fun boat.

9MM eh, I'm scared but I'll calculate it out and see what I get. I'd still leave the bottom pretty beefy, what would you recommend for the tunnel ? I went with thicknesses that seemed right and came up with an average thickness of 1/2 inch, sounds like your thinking my average thickness could be 3/8. I guess my big question is how do you walk on 3/8, I'd guess you can't use it for the deck or the topsides, maybe just vertical surfaces ? Underside of the tunnel ? roof ?

I'm guilty, never even touched a cat before and in my windows restoration biz I don't use ply at all.

OK pardon my thick skull but thats a big savings, 33lb as apposed to 50. Makes up for that extra $12,000 on the BS 1088

200 sheets at an average weight of 33lbs per = 6,600 - 35% cut off = 4,290 and I'll meet that 6 ton goal and still be able to carry mountains of veggie oil. The more the merrier on the veggie oil, I get the stuff free and its not classified as a fuel, or at least not in a car it isn't.

I'd use some of that nice ply where I didn't want to glass over a nice finish, I'm still pretty determined to at least do some nice woodwork in this thing assuming the study works out favorably. I'm still pretty enamored with the commuter style boats and I've yet to add up safety equipment for 6 as well as all the other crap I'd like to drag along. Hell I'd drag my whole shop with me if It were in any way feasible.

 

Boston: Put in water tight bulkheads to keep those 9mm worries at bay. You should be able to put a nice, big hole in the bottom of your boat and not sink if she's designed well.

 

I'm one step ahead of you on that one Cat, I was thinking of a honeycomb design between the bottom skin and the floor ply between the bulkheads to lend strength as well. That and foam fill, means I could tear a whole down the entire side and it should still hold together. Might get wet inside but should still float on the lines.

I don't have one shred of experience building a cat but I did grow up out on cape cod and you develop a pretty healthy respect for water, specially cold water. I about drowned one to many times, I'm going for the most ridiculous version of positive floatation I can think of as well as I have 5 water proof bulkheads in this thing. So far . Speaking of which they make a home insulation that is injected into open spaces, I wonder if that stuff is closed cell or not.

buddy of mine has a machine shop and he does satelite bases or used to. They make them out of titanium plates over a honeycomb latice. Wicked strong and light. I was thinking of the same thing for the bridge deck and the bottom of the hulls. 1/4 webbing every foot but on the diagonal with maybe 3/4 under and 3/8 over. Who knows, I've no clue how thick to make this stuff. I can look up hull thicknesses in my copy of elements of yacht design but I'm getting the impression that doesn't really apply to multihulls very well

 

That's right. I always say a catamaran built that way is twice as unsinkable as the Titanic

For sure you can walk on 9mm ply. Most decks will be cambered and you will have deck stringers at say 12in centres. But I would use 12mm for the underside of the bridgedeck and make that part double bottomed (with 9mm on the upper side). That's because the underside suffers the highest loadings. The double floor obviously stiffens it and also makes a convenient conduit channel

Catbuilder - where did you get your Greek ply from??

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Bos, on my lumber schedule for the Glen-L Bearcat they allow ACX-PTS PLY IN MANY AREAS
and marine elsewhere(hulls) I have seen some great ACX-PTS here in all thickness and very reasonable pricing retail 1/4" for 17.+ to 3/4" for 34+. Also if you are going to double layer use ACX-PTS as first and manine as second layer and FG over. On the ACX I use I will require the mill to issue a letter certifying what adhesive is used. I'm going to search a bit to see if cypress plywood is made. Light, does not rot, as strong as DF. Also check out exterior siding prices. http://www.glen-l.com/designs/hankinson/bearcat-cuddy-pw-bom.html
They make and sell cypress plywood---just google it.

 

Boulter Plywood. It's the best I've ever seen.

 

Go check out the site I linked to, they're about 20~40% cheaper than Boulter. Or at least as listed for retail. They also offer better than 15% discounts for orders over a dozen sheets and better still on full bunks. My bet is if I needed 200 pieces I'd be looking at 30% off, or I better, because I have a friend at United I buy from every once in a while and I'm sure he could kick the **** out of even that, if he has the stuff, I've bought him a lot of beer over the years. . The problem I have that keeps me from buying more from United is that my mill price on hardwood, which is the vast majority of what I buy, is even lower still.

 

I stumbled onto this concept while reading up on some other threads



I kinda like the idea of a manually controlled kite, winch assist of course. Seems a lot cheaper than sail and just as fun.


I made a few more attempts today to get the back end of that thing looking a bit better, didn't work but you might get a few laughs out of it

feel free to ignore the paddle wheel on this one, might have been a little to much holiday cheer if you know what I mean, but I do think the raised aft deck following the lines of the deck house looks like its got potential.



This is another group of forward studies based on going back to the flat bottom configuration and the lower bridge deck. = saves weight except for the lost structural not going with a arc section



and a really butt ugly attempt to do something with that extended deck house look I discovered in the previous.

(so ugly I deleted it)

going to try a few more things with that concept, including maybe some form of flying bridge deck and loose the aft deck. Ladder off the front for access. Course then I'm back to a forward access = leak

So far I think this one is about the best I've been able to come up with, but someone mentioned that the aft deck shouldn't be the same height as the bridge deck. Not sure if they were thinking lower of higher but so far its all up for reconsideration anyway.

 

Boston
Come over for a while, this would be a good project for you!

http://www.ebay.com.au/itm/Simpson-.../130620078850?pt=AU_Boats&hash=item1e69903b02

Late 1980's foam hulls, Roger Simpson 13.7m stretched out to 50'. Blank canvas for your restless pencil....

Bare hull and bridgedeck now, but mast/rigging, motors, saildrives,radios, tools and a load of other stuff in the pantech next to the boat. Whether there is enough extra stuff to make the price expectation work I'm not sure as there is not a full inventory. Most gear was salvaged when the previous superstructure rotted away, some accumulated in recent months.

I fear its just too big a project for me, would be too long before I was cruising....

 

I'm scared, I want to fight my battles a little closer to home. Another is the sheer size of that thing. 30' uses maybe 60 sheets, 40' uses maybe 200 sheets, how many is that behemoth going to use at 50', and then there's always parking fees. Also if the foam core went so south that the entire top needed to go I'd be really leery of the bottom half as well. I did really like the former bridge deck tho. Nice flying bridge on that thing. Might have to do a little experimenting. The salvage alone on the big bad boat might be worth it, depends. Nice project though, I'd come help for say 6 months or whatever a visa might allow.

Remember when we were kids, well at least over here, we did this rock paper scissors thing, I'm thinking the yachting world is a lot like that. Plywood instead of paper tho.

 

Australian business visas last for many MANY years. I had one forever.

 

Its looking more and more like a Lagoon to me.

Think about the ergonomics of moving round the deck when mooring or tying up to a dock. Never mind your all round vision from the wheel. That should heavily influence the layout of the aft part of the boat

And think how you'll get the dinghy up on davits and crew into the dinghy

Read up about the Calais Douvres catamaran ferry of the 1890's before going the paddlewheel route

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

I wasn't all that serious about the paddle wheel

maybe this thing

http://www.youtube.com/watch?v=mlnz-7YjWqc


my thing with props is they are eeexxxpppeeennnsssiiivvveee and you just know I'm going to finally get just the one that works best and then demolish it on a rock. If I could get away with a paddle wheel I'd do it but I can't picture making it to Hawaii, that and a paddles bound to eat more fuel in anything other than glass water. It was just another really dumb idea I tried and didn't like.

 

my latest, I'd loose the portholes, but I do like the covered aft deck area. Might play with a flying bridge a little, but all in all I think thats about it. Davits could fold up and blend into the roof structure to lend some structural support to the overhang, The launch could rest in a fold away cradle on the aft deck. Basically a big wide grating. The aft deck rail could fold down, allowing access to swing the launch off and double as a safety devise in case anyone made any efforts to drown themselves while loading.

Oh and that railing would want to wrap around the back 40 and come up over the edge of the deck to about 2/3 the way forward, then blend into the rub rail.

Its begging to have that nice fat wood skylight back. That and to scale it down to <35

 

One little tidbit... have you done any trim calculations yet? Rough ones? Or is this still in the more creative brainstorming mode?

I ask because if I were to place a bet, I'd say, as designed right this moment the bows will ride up and the stern will sink way down. Diesel aft and tender on that deck? 35'? All that meat aft as well?

You may run into some issues there.