economical coastal cruiser

[sandy daugherty]

An Australian aluminum catamaran builder uses single 50 hp diesels driving a long shaft that lifts out of the water. I believe he just uses a single universl or CV joint on an articulated strut.

Oyster: You have created a thing of Beauty

Brian, are you a little kinky about red heads? If so, we were seperated a birth! We seem to have very similar requirements....

[Oyster]

The boat should be tow-able behind a half ton pickup truck. That implies a length of less than 40', a max beam of 8'6", and a weight on a trailer of around 8000 pounds. It should not have so much draft that it would require a steep ramp for launching. The boat should not exceed 3'6" draft when fully loaded. Serious bonus points will be awarded if all this stuff will squeeze into a standard shipping container.

The boat should not require custom castings anywhere but the propeller: mid range off the shelf components will be used for windows, hatches, plumbing, deck hardware, etc. Decks and wall where windows and hatches are mounted will be flat.

There will be enough fuel on board for 600 miles at cruise, with space reserved for additional long-trip bladders.

Among numerous other items, you are kidding aren'tchu in the above snippit? You have defied the laws of reality if you plan to launch and retrieve an 8,000 pound boat with a 1/2 ton truck for starters. You need to consider a much larger tow vehicle or a smaller boat today, period case closed.

[Willallison]

Originally Posted by Pierre R

I can talk a bit about high house loads and low power engines. My boat is a 4 ton full displacement hull driven by a 13.4KW Sabb diesel with a 490mm controllable pitch propellor. I get up to 16 mpg at an s/l ratio of 1.15. House loads that I can have is a 150 amp 12V alternator, a 550watt air conditioner, electrical needs and a 850 watt coffee pot that tends to be on.

The 150amp alternator is driven by a single V belt and probably does not turn up to full power due to the fact that a the Sabb is normally turning at 1450 rpm with a 2:1 reduction.

If the GD coffee pot kicks on you can kiss three tenths of a knot goodby and waste an incredible cup of diesel a day running that power hog appliance. Seems a good price to pay even though its anoying to have the big change in sound and speed just cuz the coffee pot kicks on. Its about the same load as putting the paravanes in the pond to stop the rolling. My fuel bill for 2,985 miles of travel was $432 USD or 7% of my operating budget. I have trailer this boat all over the eastern US and Canada. Perhaps I should look at optimizing the prop eh!.
http://s706.photobucket.com/home/PierreR/index

Well... though the speed is quite different, that sure brings everything back into focus a bit - thanks Pierre! Is that a production hull that you've added a new top to?

[Oyster]

Thats an interesting boat. But is that the trailer that you have towed the boat on up and down the country side?

[sandy daugherty]

I'm sure you're right Oyster, you have had the experience. I was using the advertised towing capacity fro the truck manufacturers: Dodge 1500 = 8,950#, Silverado 1500, 10,250#, etc. That might work for flat-land hauling, but will surely suck in the hills.

I towed 4000# behind a five speed 120 hp Trooper but did a few Kentucky hills in third gear. The truck gave me another 50,000 miles without a problem, and it braked all that pretty fine.

Now why would you suspect me of frivolity?

[Oyster]

Originally Posted by sandy daugherty

I'm sure you're right Oyster, you have had the experience. I was using the advertised towing capacity fro the truck manufacturers: Dodge 1500 = 8,950#, Silverado 1500, 10,250#, etc. That might work for flat-land hauling, but will surely suck in the hills.

I towed 4000# behind a five speed 120 hp Trooper but did a few Kentucky hills in third gear. The truck gave me another 50,000 miles without a problem, and it braked all that pretty fine.

Now why would you suspect me of frivolity?

LOL! I am a GM feller myself, been one for years. But I have never been able to tow 8,000 with a stock rearend and would never attempt a long haul without some serious gear coolers and a modified rearend and altered shocks. But the 5.3 which is standard now after the 4.8 just does not get it at all. The tongue weight along will cause you some steering issues. The Duramax will do it for for sure. The 2,500 will do it but you need a fuel tanker to follow you for sure. I have a feller aquaintaince with a Trooper too and he tows a big Sea Ray and gets about 8 mpg. with that amount behind him.

[Pierre R]

Originally Posted by Willallison

Well... though the speed is quite different, that sure brings everything back into focus a bit - thanks Pierre! Is that a production hull that you've added a new top to?

Yeah, I believe its a Charlie Morgan design produced by Permacraft from about 1968 to 1979. They originally came with Perkins 4107's and many were delivered with a foot more draft and motor sailors.

The pilothouse is e-glass epoxy over white eastern cedar.

You are right that the speed is not exactly 12 knots but she will take Lake Erie in stride.

[Pierre R]

Originally Posted by Oyster

Thats an interesting boat. But is that the trailer that you have towed the boat on up and down the country side?

Oh no, I have a tri axle trailer for her now.

[Brian@BNE]

Sandy! Welcome back! What fabulous hour or so of posts you led off! I just checked the mirror - what hair i could find is grey, and i don't recall it ever being red. Might even be enough SOR now for Will to get busy, and he still has time before the Wooden Boat competion closes as well.

Pierre - nice boat and specs. But I have 3500kg max including trailer so I'd have to surrender something. Not the coffee pot though. So folks please don't use all of those lbs Sandy is lettting you have.

Even then, slippery ramps will lead to some anxious moments - 4WD for me, and a rope onto another vehicle up the ramp for insurance occasionally. Sandy did say barely trailerable, so we are going to have fun on ramps and hills. I'll add to Sandy's bonus points for being able to fit through a containers doors so I can leave the hils to others.

Tad's post of the Topaz design got me thinking. I had to smile with the specs, particularly the beam. Room to spare in the container! Of course I'd want to stretch it by about 5', if I could. And the coach house is yet to grow on me. But of real interest is the stern section, particularly if we dont leave it flat all the way. Could we hang two of Pierre's 490mm CPP's back there, one on each side? Shrouds (or nozzle housing) around them that had built-in rudder vanes also. Can we get enough room without going beyond max. beam and 3'6" max draft? Belt drive from single motor which can be raised or lowered (just a little bit) to tension belts to both sides simultaneously. On the trailer the props would need protection - perhaps demountable props, and a fifth wheel trailer would work. Such a trailer will feel more comfortable to tow with the pickup truck, is better slso in that trailer wheels can be further back to reduce overhang. But alas! A fifth whell trailer will mean a shorter boat - I'll have to re-read the regs to see by how much.

[Willallison]

Originally Posted by sandy daugherty

What did I miss?

Budget.

[Willallison]

Oh... and have you ever heard the term compromise?
If not... you will

[Guest625101138]

Originally Posted by Willallison

...
We should all be open to continued learning. Tel me... what did you learn from this...?
Compromise

MikeJohns has offered a quote on what naval architects should aspire to that I totally agree with.

I have attached it because it bears repeating on this thread. NAs with this outlook are the type I engage. Those who are happy to compromise on my behalf because they view it is as not worth the effort will not last long in my employ.

Rick W

[Willallison]

Originally Posted by Rick Willoughby

MikeJohns has offered a quote on what naval architects should aspire to that I totally agree with.

I have attached it because it bears repeating on this thread. NAs with this outlook are the type I engage. Those who are happy to compromise on my behalf because they view it is as not worth the effort will not last long in my employ.

Rick W

I'll let someone else respond to that....

[Brian@BNE]

I see resolving the incompatibilities noted in Rick's thumbnail as compromise (even if others would use the word differently), which I'm happy about occuring if I know its happening and can have input.

Will - no budget from me yet, but like Sandy it will be home built with appropriately light and cheap materials. I am learning slowly. Whatever can be light will be! Cheap is important as mine might yet end up as 'Heath Robinsons boat #1' and have to be turned into firewood after its maiden voyage. No, actually, there is enough experience and wisdom here to ensure by the time I pick up the tools I'll be confident about performance.

I might get off the belt drive theme though. Farm machinery (and some mine machinery) often has 90 degree drives which might just be in the right power and gearing range, and like Sandy I believe off the shelf (other than your local marine chandler's shelf) is gonna be key to cheap as well.

[Guest625101138]

Originally Posted by Brian@BNE

I see resolving the incompatibilities noted in Rick's thumbnail as compromise (even if others would use the word differently), which I'm happy about occuring if I know its happening and can have input.

..

Brian
Clients are always right. They have the responsibility to compromise on THEIR requirements in order to resolve incompatible requirements so a design can proceed. The designer needs to be UNcomprimising. He should work to his capacity to find the limits in order to correctly articulate why the requirements are incompatible.

I took exception to the idea of arbitrarily compromising on an outboard without any reference to how it would constrain the design.

Within the initial requirements of fuel consumption at given speed it can be deduced that a diesel with a 600mm prop can haul twice the displacement of one powered with an outboard. I believe this is a large difference and something the client should be informed on.

I did not know this until I worked through the exercise and I doubt many others did as well. So any designer would be sadly remiss to not point this out by suggesting it is not worth the effort.

Rick W