New design - opinions / idea's wanted

[northerncat]

Originally Posted by KIWI

Have a look at Pelin designs, He is a NZ designer and would be one of the best known designers in NZ , I have seen one of his cats a 40ft and even though I am not a cat person I was impressed this one was home built and the owner did a amazing job, I was also impressed with the bridge deck to water clearance of about 4 ft , He has a 40ft and a 45 ft in the cat designs and can be built out of ether cold molded marine ply or FG
Pelin Boat Plans - Build Your Own Boat

Graham

other than prices for the plns i couldnt see any info on the cats he designs where were you looking??
sean

[BigCat]

"The design was a joint effort between Dudley Dix and Phil Harvey." I don't think Dudley Dix made that drawing-it shows interior features where there is surely no boat due to flam (often miscalled flare.) There is much less room inside a hull than that drawing shows.

[Abaco]

Big Cat,

These are strait off the Dix web site:

DH 550 Plywood Cruising catamaran

[BigCat]

Originally Posted by Abaco

Big Cat,

These are strait off the Dix web site:

DH 550 Plywood Cruising catamaran

No, it isn't. You've been tinkering with it, though I admit that it is a pretty slab-sided design, and the (designed) waterline is remarkably close to the deck line. In your version, they are identical. In his version, the berths are inset slightly, and the cabin sole is inset quite a bit. If you look on my website, you will see drawings that illustrate this more clearly, as the designs shown there have more flam, and so the effect is clearer.

[Abaco]

Big Cat,

These drawings where given to me by Phil Harvey in PDF format. I have neither the technical expertise or the desire to alter them. It doesn't really matter. A posted them to give someone an idea of beautifully designed cast that are currently available. That is all.

[BigCat]

"These drawings where given to me by Phil Harvey in PDF format." Hi, Abaco

My point is basically that the an interior won't go to the deck line. Lots of people try to draw interiors drawn to the deck line, as in a house plan, but boats taper as you go lower in them. This is important because not understanding this is common, and it can lead to over estimating what can be placed inside a give hull, and how large it is. The drawing posted showed the interior elements going to the deck line, and I knew Dix wouldn't draw that, as he knows better. (I think he's a really good designer.)

TD

[Steven Prince]

Abaco,

I already know of the design, i was originally planning on building one of Dudley Dix's monohull boats but changed my mind, having already spent the £1000 odd pounds on the design. I did enquire about the design that you've shown but although i liked the majority of the boat there where certain features i wasn't keen on, and as i only plan on doing this once it has to be right the first time.

JCF and other with freeship experience,

I got the design into freeship but the statistics coming out couldn't be right, the waterline length for a start that it was saying is way to big. Does anyone have any experience with inporting a vrml file and then getting the figures out.

Everyone,

Ok, generally question about paint and core material, everyone seems to be of the opinion that black as the hull colour and having a foam core is out, would black be ok if the core material was wood.

[Steven Prince]

For those wondering how you get between the bridgedeck and hull I've attached a pic showing just the hulls to show, The doorway is 1.9m high.

[Southern Star]

Steven, it appears as though you have changed the design of the house from your earlier drawings (Feb 2nd) and that the full height of the coachouse now extends out over the hulls. That should certainly solve any problems of ingress/egress (although I anticipate that you will still need to have the opening extend all the way up to deck level).

As you are no doubt discovering, this is a monumental undertaking. Have you given any thought to hiring an established naval architect to either modify one of his stock designs, or alternatively, to work with your imput to create your one-off dream boat?

I am certainly not attempting to cast aspersions on your capabilities - and I fully understand your motivation. When I needed a design for the small resort I am now having built on Margarita Island, I did the initial architectural drawings including plumbing, wiring etc. I then hired a local architect who, in conjunction with a stationary and an electrical engineer, 'refined' my plans. They are a significant improvement in terms of readily available materials and the ease of construction (and therewith, of course, cost). They also made some very valuable improvements in terms of subsequent maintenance ( for example, separate main sewage access points for each unit). Afterall, this is what they do for a living and you should consider letting their experience and expertise augment your own.

Brad



Brad

[Steven Prince]

The house is still the same. If you look at the enlarged picture from the 2nd feb you will notice the hull has a raised section, the bridgedeck is then higher.

I plan on hiring someone in towards the end after i've Completed the bulk of the work. The CAD system i am using means the models are easily updated.

I do not have the finance available to employ someone to do all the work, neither do i have the desire to get someone else to do it as they still won't be able to achieve everything i desire.

[sandy daugherty]

I've read your thread with great delight; I too have been dreaming and doodling for a very long time, and I know how sad it can be to see some cherished feature expire in the harsh light of practicability. Other times I've been more than a little hacked off to discover that some brilliant new concept had in fact been repeatedly tried in the past and failed because of some not-so-obvious-to-me fatal flaw. So before I launch into a catalog of no-you-don'ts, good on ya! Keep the dream alive! Michael Angelo is remembered first for his incredible successes but second for his wildest, if impossible fantasies. All of his work continues to inspire us today.
The A frame mast is not new. Historical records at the Smithsonian show attempts further back than the American Colonial Era. The reason that they have not worked well enough to be seen on production vessels today are a. windage, b. weight aloft, and c. structural problems. All these reasons may be overcome some day. While windage and weight aloft are self evident, there are some structural problems you may not have considered: Catamarans are not rigid structures. Encountering waves or gusty winds, one bow will imperceptably lift before the other. One stern will drop more. The resulting flex is fully accomodated in a tripod rig or a conventional forestay-backstay / upper and lower shroud system. The A frame will undergo exceptional loads because it triagulates this distortion. The loads become massive and are infinitely repeated. You will either have to build in the rigidity of a concrete blockhouse, or accomodate (and predict) the flexibility required with shock absorbers and torsion bars. Its not impossible, its impracticable.
Another impracticable dream is the forward canting mast, to carry the loads of two highly tensioned forestays down a backstay (or two) tied to the vessel on a very short base. Finite analysis is perfectly capable of calculating the load on that backstay(s) but materials science hasn't come up with the structure that can hold that load if its made of anything but unobtanium! We're talking about the kind of loads a large self-propelled crane would carry, and it don't float good. (redneck humor)
Ahh, the sustaining dream; a black boat. In the tropics.
item: A sunshower is a shiny black plastic bag, that heats a gallon or two of water to 105 degrees F in two hours in the tropical sun. A shiny black plastic boat in the same sun for a half a day heats a human body to the same temperature achieved in a Japanese torture chamber during WWII. Said chamber was made of cast iron, and it wasn't even black. Not a big tourist draw today.
Item: UV radiation increases so much in lower lattitudes that many vacations are ruined in the first half hour. GRP is so susceptible to UV that virtually all boats are white, and their gelcoat exteriors are full of UV inhibitors. Even so, the structural strength of fiberglass boats experiences a predictable downward curve when exposed. A structure that has a thirty year service life (80 % original modulus of elasticity) in the temperate zone has a ten year service life in the tropics. Paint it black if you want, but don't sail it any further than you can wade.
Item: Hobie Cat sold a number of 16 foot boats with wild sail colors and black anodized aluminum masts and seat rails. I still have a scar that isn't seen often, and I never got south of Houston.
Item: Use a paint that turns black under 75 degrees and it will turn black In Belize between 4 and 5 am. You can get up and look at it then. Or sail back to England and take a picture. Easy.
Item: You think you'll just stay out of the tropics so you can have a black boat? Buy a motor home. Paint it black Make sure it fits in the Chunnel.
Suggestion: Paint the INSIDE black. Some tasteful recessed neon lighting might help.
More suggestions, serious ones this time. You have a fresh eye and a demonstrated dedication to original design, so doodle these ideas:
Make the A frame idea work with shrouds some how linked like the parallel ruler on a drafting board.
Let the boom swivel at some point aft of the tack so it would be partially counterbalanced, like a spade rudder. Reduce the loads on the main sheet.
Rig bullet-proof reefing, that can be taken in under load in adverse winds, by a single person.
Make one of your electric propulsion motors regenerating to put back in your battery bank what you used to get out of the harbor.
Keep enough capacity to power into winds and waves for a day, simply because you will have to if you go off shore for any longer than a week or two.
Lay up HF antenna radials of 3' copper foil in the deck for a counterpoise.
Two words:"kayak garage". Or "bicycle storage"
One word: "Scooters"
Did you know you will get hooked on diving and snorkling? A good platform for swimming and unloading a dinghy doesn't have to be on a transom.
A couple not-to-deep top loading, supremely well insulated, totally solar powered refrigerators. One in the middle of the dining table.
Unobstructed views of all four corners and all sail-tails from each helm position.
Four words: "Kort nozzle joystick maneuverability."
Finally: Bullet-proof simple-to-build, easy to maintain centerboards and kick-up spade rudders for leapfrogging over submerged shipping containers. Patent them. Send me the royalties. Keep at it.

[Lodesman]

Originally Posted by sandy daugherty

The reason that they have not worked well enough to be seen on production vessels today are a. windage, b. weight aloft, and c. structural problems.

With regard to windage and weight aloft, do you say the same thing about all vessels with more than one mast? Ketches and yawls are out? And bi-rigs are out?

Since the 2 sides of the A-frame provide mutual support, they don't need to be as beefy as a single mast. In fact, the whole structure could be made lighter than a single mast set-up, so weight aloft is not an issue. As to windage, there may be more, but compare the additional windage to that of the dead sail area in a conventional rig, and I think the A-frame would have the advantage.

So that just leaves structural problems:

The A frame will undergo exceptional loads because it triagulates this distortion.

You're going to have to explain what you mean here. And please compare these exceptional loads to those generated by a conventional rig on the centre of the crossbeam.

The loads become massive and are infinitely repeated. You will either have to build in the rigidity of a concrete blockhouse, or accomodate (and predict) the flexibility required with shock absorbers and torsion bars. Its not impossible, its impracticable.

Check out the SMG website - doesn't look like there are shock absorbers and torsion bars on that A-frame.

Let the boom swivel at some point aft of the tack so it would be partially counterbalanced

Don't need a boom on an A-frame.

Your post was full of 'it can't work', but had little substantiation to those claims. I'd like to hear your proof, please.

Kevin

[henryv]

a good reference Home

[imagine2frolic]

What ever happened to the Harken boat with an A-frame? I once saw it coming out of Ft. Lauderdale soon after it was launched. How long ago was that???????????

[imagine2frolic]

PROCYON project........a Bold experiment - Boat Design Forums

Let me answer my own question, and with a pic too................