35' cat concept for the inside passage.

still kinda just brainstorming, my theory is that with the inside being as of yet a blank page I could wiggle little things like engines and mechanical to where they might need to be in order to better balance the structure.

There's always a way, its just a mater of remaining flexible.

Lagoon ? I'll have to look that one up.

 

Probably the most common catamaran there is. Very many of them out there. Despite being tubs, they hold their value.

 

e gads it does look like a tub. two tubs actually and a mast but still, I do see a resemblance.

on the bright side, at least Richard thinks its starting to look like something, although a bathroom fixture wasn't quite what I was after.

 

Hi Boston,
I aim to rattle your cage a little, Keep the underwater sections symmetrical - easier to build and align and will steer straight even in a downwind run or a beam-on sea... lift one hull and the imbalance will assist in a broach etc... and all for what - no advantage in performance... Look at the bottom of the chamberlin hull and the shaft is short (no drag) and the propeller protected... it is 10m loa and powered by 50 hp a side for 15knot max... weight is well under your 6 tonnes - in fact near half that... http://www.chamberlinmarine.com.au/ and http://www.chamberlinmarine.com.au/news-a-events.html

Also, the windows at the front in your sketch do not work on a cat, a brow to shade projecting 6 or so inches and the windows tilted back so reflection is not off the white painted 'ceiling' but the carpet underfoot - a lesson I learned too late and night piloting is a right pain in the ***.... Hence the hatch over the wheel where I stand on the 'captains-chair' with head and shoulders up in the elements, steering by bare toes grasping the wheel....

 

hmmmmm
was it the type of glazing you installed or the color paint you used. Gloss = glare, also poly has entirely different refractive qualities as glass.

Good point though I'd have to look into that before I committed to anything



maybe if I used non skid gray with sand fill on the decks it might not reflect so badly. My bet is the glare off the moonlight is coming up on a glossy surface. Maybe, but its a really good point you raise there mate.

Might just be a mater of finding the right combination of materials

Oh and I'm not to spooked by the asymmetrical hulls, I'm not sailing, or at least not in the traditional sense, kite maybe, but no masts or rigging to speak of, that and all these guys doing power cats have asymmetrical hulls, must be something to it eh

 

Hi Boston, I was referring to the visibility at night out from inside... It is nice to have a flat white ceiling for an even spread of light in daytime and not so much heat radiation and the windows you have looking forward from the bridge deck will ensure the reflection you will see off the inside surface of the windows is any light reflected off the ceiling, tilt the windows top inwards and the reflection will be your bronzed chest, a dark shirt or the carpeted floor... My windows, being vertical ensure I have a good view aft by reflection but not so good forward - sort of like the modern laptops outside - almost impossible to see what is on the screen but a delight for the ladies seeking a handy mirror to check the lipstick or the coiffure....

So what is the advantage in an asymmetrical hull? - - More difficult to build and set up perfectly PARALLEL... Why do it, - if there is no real/significant benefit/advantage, symmetric build is easier to do... Or are you one of those pioneers who appreciate the "hard way" - - - (seeking sexual experiences standing in a barbed-wire canoe whilst paddling upstream away from the edge of Niagara falls...)

The difference between grey and white in heat absorption is astounding... My white decks with 'sand-anti-skid' is not an issue (glare etc)... - Polarised 'sunnies' are an the bridge as it helps see through the water...

Large area of the foredeck is the open weave net (black & no knots) as used in the salmon nets for fish farming operations... Very durable quite comfortable to lie on and walk over and convenient as an outdoor relaxing lounge with sundowners.... I can also see through the weave at the anchor chain and bridle as well as any near surface objects...

 

yup thats what I was thinking you meant, looking out from the inside and seeing glare off the surface of the outside because of the angle of the glass. But there's got to be a way around it. Glass refracts light differently than poly anyway, so I'm thinking with polycarbonate lami the issue might be moot. But its a good point you raised. Well worth testing out before one builds anything.

Also I'll be primarily in the PNW so I'm ok with gray instead of white. decks. I can always slather a new coat of paint over it if I get tired of the colder climbs

I think the asymmetrical hull probably "pinches" less water between the hulls than a symmetrical shape.

I want a grating for the back 40 so I can sit and have a nice meal back there from time to time. That and a place for a barbecue and smoke oven

Now that I have something resembling what might be a pleasing shape I think I'll pear it down a little, small as I can get it and still keep the proportions

OK dog is starting to eat the mat I place under his bowl, might be time to feed him

cheers
B

 

Hi Boston,
The reflection (not refraction) was from the stern light shining on the rails on the "back verandah" and also the security screen/flywire just forward and the windows in front looking forward reflected that and my face lit up by the instrument lighting (mainly the plotter screen and autopilot digits etc.)...

Once you have mastered the art of joining marine grade plywood sheets then joining them and covering that with glass both sides then laying the cut full length pieces on a frame of bulkheads also made of glass sealed marine grade ply - - and get an engineer to determine the thickness needed... - Remember the CSM boats used to be less than 1/8th of an inch thick and the "brag" was that it was stronger than steel ???????????

With shelves set (particularly below waterline and near where bumps from other boats and wharves may occur) providing cheap, efficient and robust skin stiffening and strength... I used light balsa-cored-duflex(400gsm glass) for some of the shelving and 3ply marine plywood covered with 400gsm glass for others... That was above design specifications as I wanted open shelf space...

If I build again (likely) it will be a very similar design as the hulls are very robust and handle waves beautifully but in ply with glass over so I have less worry about bruising from underwater bumps and wharves etc (cosmetic that must be re-sealed to ensure water tight integrity)... The bottom has 3 layers of 7mm ply with glass over both sides of each sheet/layer...

It is not that which will slow you down but the wave making tendency so a hull shape that does not make waves is desirable and a beam that does not have the wake from the other hull hitting the inside - or something like that Leo is the expert on that... A simple hard chine shape such that you cut four plank shapes for that chine board - too bloody easy and the asymmetric shape will create more problems than it solves, remember KISS and go symmetrical - looks better too....

 

refraction is why you get reflection when glass is at an angle like that Mas

if your glass has a lot of reflection in it and its flat then you might think of a different window cleaner. But some angle is desirable to help reduce deflecting images, there's a balance in there somewhere

 

Ahhhh, OK

 

All what guys?

Are they all designing lowspeed displacment hulled cats?
or are they higher speed?

 

you's guys

I was just looking at MR Woods designs of power cats, and some others and although I'm sure there are symmetrical hulls I'm not really seeing to many yet.

Kinda looks typical of power cats to have an asymmetrical hull design. But thats from about a one month look at cats, so I'll most certainly defer to the more experienced hands.

 

Bos, that looks to me like a whole lot of topside glass and will be used in waters that can get quite rough.

 

storm covers

Not sure what the Dashew's did with all there glass in case of storm but I'm thinking some covers for doing any crossings or in case of rough water. That and I'm loosing the port holes

Oh and that Lagoon power 43 is nice. Love the aft area on that thing.

 

lagoons nice but its just to big. I want more service options than are available to a larger boat. Ideally I'd be able to beach this thing. One thing I really like about the cat is its so easy to get at most of it.

It needs an instrument tower. I toned it back down to 35' and am working on narrowing it up some. From 17.5' to something like 16'. The forward elevation is pretty well set other than width, Trawler style windows all around with hard points for installing storm shutters. The hull configuration ( that whole symmetrical or asymmetrical thing ) is completely up for reconsideration as is the entire interior layout. The smaller I can make it and still have it be livable the easier it is to maintain it.

Its a day tripper/charter/eco tour boat/live aboard. I'm thinking bunks for six but damn comfortable for 2. Great room style deck house. Someone suggested that you should be able to see as much green as possible when you open up that back door and I think they nailed it.

Cheers
B