35' cat concept for the inside passage.

[michael pierzga]

Two important areas in the general layout are often neglected.

The work station and the reading station, library.

These are the areas that you will spend the most time in.

Worthwhile devoting substantial space to these high use areas.

[groper]

Originally Posted by Boston

Actually I think I'm going to take this one and start tweaking it...



I'd carry the bridge deck all the way back and include a lot of that space in the cabin arraignment, I'd loose the groovy sloping sheer of the hull and replace it with something that offers a little more buoyancy and head room, and I'd leave all the nice woodwork to the interior space. Those cheap ass looking windows aren't going to fly tho. And I'd want to build it in ply still.

Its ten meters or about 33' so I'm going to stretch it up to 35. change the design of the windows but keep the basic layout for now. I suppose my target weight should be the same 4 tons but I'd loose the cedar strip planking and go with marine ply.

This is fantastic news boston, that chamberlin cat is one of the best ive seen in this size range, you you can adpapt your own styling to it, it would be a wise move - i too dont like the styling of that boat at all, but its form and function make a good starting platform.

One question tho, why loose the cedar strip planking? Cedar strip planked hulls, laminated with fibreglass/epoxy both sides, is a very strong yet very lightweight build method...You might find a use for it below the waterline or wherever you have tight or compound curvature - should you introduce this shape into your design that is... At one point, i was thinking of using okume ply for the topsides which had little curvature, with ceder strip planked hull "shoes" below the waterline as there was no way i could torture the ply into the curvature i needed down there... always keep your options open, in the end, you may use a combination of many methods and materials to get the job done...

[Boston]

the style lends itself to plywood construction, so lets see where it can go. I think the windows need work. They look like the same ole cheap trailer windows found in any camper from the 70s era. I'd likely put in a row of smaller windows all with the same rake as the forward glass. A wood interior finish and a glass over ply+foam trim, exterior. The goofy sheer line might have to go as well but having drawn it up once already with a straight sheer and a few small windows rather than one huge one I can see its going to be a challenge to make it look like anything other than what it already is. In which case I'd just be plagiarizing someone else's work.

I'm beginning to understand why every cat in this size range is so amazingly butt ugly. Its just really hard to cram everything in and still manage to make it look like much. As it sits I'd consider the chamberlain a weekender, not a guide/liveaboard.

[rasorinc]

Bos, I have been where you are now in regards to design changes to a Cat. Why don't you challenge yourself a bit and limit the beam to 10'? All states allow 10' to be trailered
W/O flags or signs or lead cars. They just want you to buy a $ 100.00 permit. Then you could move the thing with your snake oil burning pick up. If designs you want cannot be done in 10' then go to 12' then you need flags and signs but no lead cars.
Above 12' you need everything to tow it including special days and hours. You can do this, I know you can, and it will be in your price range ( which is everything ). At least give it your best effort. And YES do it in wood and heritage style. Stan
PS in 36' or 38' you can sleep 2 couples + yourself in comfort. Also each bedroom suite will have their own Full bath--no tub, a shower instead. I assure you it can be done.

[Boston]

I was also looking at this thing. I know its built out of some pretty crappy ply but the design of the hulls lends itself to a very easy build and some accommodation for a more "heritage" style as Stan calls it.



It might also be interesting to explore the option of extend-able hulls. I'm not sure I can jamb everything into a 10' beam but I could use some box beams with actuators to extend the hulls on arrival. Trailer-able is extremely appealing.

[sabahcat]

Originally Posted by Boston

I'd carry the bridge deck all the way back

Be careful
The arse end may not take that additional weight, especialy as you dont seem to want to use lightweight construction techniques , which cam make all the difference between having a cat that performs or a DOG

[rasorinc]

The Glen-L Bearcat designed by Ken Hankinson, NA is 28' x 10' or 11' option. You can use the basic structural design to do anything you want. $15.00 for study plans and they show all the structural designs that go with the boat. Well worth the bucks for a solid learning experience. And you get a complete materials list with grading specs. (wood )

[Boston]

yup and thats another issue, if the style doesn't lend itself to lightweight construction then it might just not fit onto a cat frame and still come up acting like a cat.

Which means if someone likes a particular style of finish they might just find themselves restricted to only certain types of boats. Which is another reason I was thinking sharpie type hulls because they are efficient and can hold tons of weight. Shallow long skinny hulls, not long narrow and deep. Holds more weight with less water pressure added to the hull. Water pressure = resistance, depth of hull = more water pressure = more resistance. The sharpie hulls just doesn't draw that much water, so it slides along just fine. The box type keep I'm seeing under that Chamberlain is efficient but maybe not within a wide enough weight range. Once I pile a few fat tourists onto this thing its still gotta move well.

[sabahcat]

Originally Posted by rasorinc

The Glen-L Bearcat designed by Ken Hankinson, NA is 28' x 10' or 11' option. You can use the basic structural design to do anything you want.

I seriously doubt that

http://glen-l.com/designs/hankinson/bear-cat.html
A vessel designed for open boat


Or cuddy cabin


and with low bridgedeck clearance


Has no hope in hell of having a large structure plonked on it and being successful, let alone seaworthy.
What you have recommended or suggested,would be downright dangerous IMHO.

[WestVanHan]

Well now that you've made this decision,there are many power cat designs out there for you to scavenge the parts you like off of.

[groper]

Originally Posted by Boston

...Which is another reason I was thinking sharpie type hulls because they are efficient and can hold tons of weight. Shallow long skinny hulls, not long narrow and deep. Holds more weight with less water pressure added to the hull. Water pressure = resistance, depth of hull = more water pressure = more resistance. The sharpie hulls just doesn't draw that much water, so it slides along just fine...

Youve made alot of incorrect assumptions here...

If you have a set DWL length, you can really only manipulate depth and width to arrive at your designed displacement. So, you cant have you cake and eat it, its either skinny and deep, OR fat and shallow assuming same displacement and length! Most catamaran designers end up somewhere in the middle, making them just fat enough to allow the desired accomodation spaces to fit, whilst not compromising the performance too much... Hence slow fat cats, or fast skinny hull cats that arent as roomy inside...

And, its actually better to go deeper rather than fatter from a resistance point of view -Resistance has many components, but one of the largest components is wave making resistance and this is largely influenced by waterline beam/length ratio- hence skinny but deep has less resistance assuming the same basic form, displacement and waterline length...

More to the point why sharpie hulls do well, is that they have a high block coefficient (very square in body plan view) this means they can have a narrower waterline beam and depth to acheive the same displacement as a round bilge hull of the same length. So within certain phyical regimes, the resulting reduction in wave making resistance (thanks to the narrower WL beam), often more than makes up for the increased wetted area when comparing the flat bottom and steep sides hull shape, to a similar dimensioned round bilge hull shape...

Ive done quite a bit of CFD hull modelling which is the basis of these assertions...

[sabahcat]

Originally Posted by Boston

I was also looking at this thing. I know its built out of some pretty crappy ply but the design of the hulls lends itself to a very easy build and some accommodation for a more "heritage" style as Stan calls it.

easy enough to take a hull shape like that, made from ply if thats your thing and add flair even if on one side (inside) only giving you easy access into and out of the hull.




For the life of me I dont know why you would want an inefficient slab sided box hull like you propose when for a small amount of extra effort you can build far prettier and more efficient hull shapes.

The hulls will probably be the easiest part of the build anyway.

[sabahcat]

Originally Posted by Boston

The sharpie hulls just doesn't draw that much water, so it slides along just fine.

Wetted surface area for given displacement would probably be similar .
Pounding will certainly be more
Resale will certainly be less

The box type keep I'm seeing under that Chamberlain is efficient but maybe not within a wide enough weight range.

Its an efficient boat for a couple and occasional guests which was probably the design brief.
Rest assured though that the hull form is a good one, look to Tennants many passenger ferries for evidence,.

Once I pile a few fat tourists onto this thing

which is why most are saying that 35 is probably to short, if you still want efficiency.

its still gotta move well.

Define "move well"?

[rasorinc]

I would suggest the expert on cat hulls on this forum is Alik and hopefully he will chime in
on your plan Bos. I am certainly NO EXPERT.

[rasorinc]

Here is a nice look Bos.http://www.boatdesign.net/gallery/sh...hp/photo/12370 PS sent you a PM