why a trawler? why not lite and lean?

[seafox]

Reading Dale R Hamilton's thread about his dream 48 footer and the cost of $400 K I have wondered why the trawler ( say we define it as a heavy relitively deep draft some what blunt load carryer displacement craft) is a design choice.
Mr Bolger has a (32 foot?) design with a boaty hull based more on the dutch craft for a couple to retire on and say spend the summer in maine and the winter in the caribean. but he also has that "super sharpie bolger box" he designed for an austrailian client of about 50 feet ment to sail to europe then fit in the cannels of the contenent? ( don't remember if it would be the long boat style size to fit english locks belive the width is 6 foot 8 inches beam? and what 65 feet long?)

but the designs that intreague me are the narrow shallow draft tri hulls and the wave peircing long lean monohulls craft where smaller engines mean lower costs better fuil economy. lower cost ( as mr Bolger said in the first small boat journal story of his I ever read, about a 16 foot tug boat 'boats cost per pound'. the length of the boat was driven by a new state tax on longer boats.) it should also be noted that boats over 10 metres face extra laws and regulations.

on the other hand if you think the compairison between a trawler design and a wave peircing design is something like a monohull vrs a sailing trimaran where the former depends on ballest to stay upright and the latter o more on form.... some studies I have read indicate that 40 foot multihulls are about the minium of safe size for off shore I wonder if ultra light long lean boats need to be over 40 foot before they become safe?
then their is the comfort level where the quick movements of a light weight craft wear out the crew and endanger judgement. and would the heavyer craft shorter broader be stronger ( remembering the ultimate storm movie if the hull had not been comprimised by the paravane would it have righted itself insteed of flooding and sunk?) or would a higher displacement speed of a longer craft with a smaller imerced cros section be able to outrun a storm?

thankyou for your thoughts
Jeff

[ 03-10-2006, 12:51 AM: Message edited by: seafox ]

[Ian McColgin]

Displacement is the measure of accomodation. William Garden designed a lovely long low powered thing - I'm sure some forumite will recall the strangely named boat and get a post up. She was built around the owner's antique engine and is maybe 55' long and a couple inched wide. Runs easily at 10 knots. But that narrow and shallow an envelope means little displacement which means little room.

Granuaile had plenty of displacement - 20T - packed into her 55'x10' with a 6' beam and she could power on flat water at almost 7 knots with a but 20 HP engine. Windage becomes a factor quickly, of course.

In the Compleat Cruiser, LFH shows a wonderfully narrow motor cruiser but the design was never what you'd call a hot seller.

Point is, you can make a wonderful narrow boat and it will have some most seaworthy attributes. It will likely be a bit hard to maneuver close in unless you tart it up with a bow thruster. I'd go with flanking rudders myself but anyway . . .

And the thing will cost you an arm and a leg at every marina, haul-out, etc where they charge by the foot.

It also will have only modest load carrying compared to the trawler model. When you liveaboard, unless you're the Carr's or somesuch, it's nice to have your tools and toys, all of which take displacement.

It's a choice.

G'luck

[Tom Lathrop]

Ian,

I think it was called the Tklingit after the indian tribe. They were so proud of that big engine that it was in a glass case so they could look at it and watch the various rods and rockers operate while it slowly turned a big prop. No room for anything else in the boat though.

[Dan McCosh]

I think PDQ catamarans now are building their boats without sails. They make a stable, efficient platform that has lots of liveaboard room, good fuel economy, etc. I know one guy who is in a wheelchair who bought one to cruise in the Bahamas--trading in his old sail-powered car. This could be the most efficient approach compared to trawler designs. I also know one guy who tried a trawler for a year or so, and couldn't take its motion at sea--went back to sail.

[rbgarr]

Here are some interesting lean passagemaker designs:
http://www.tadroberts.ca/passagemakerlite.html

[Ian McColgin]

Tom, I think that's her. As I recall, that huge ancient engine had very little power.

I have sometimes imagined a sort of a cross between Tklingit and the larger dory like cruiser that Gurr (sp) has designed. But then, being a rag and stick guy, not a monkey wrench sailor, I'm already well used to six knots on the cheap.

I like simplicity and structural integrity, which leads me away from multi-hulls, wonderful in their way but such highly stressed structures, especially in a seaway.

Another problem with multi's, rather the opposite problem from needle boats, is that dock space will be expensive, if available at all. Harder to just idle in to Wally's for a great dinner.

(Yes you Intercoastal buffs, that Wally's down Wrightsville way or some such.)

[mmd]

Cats are very weight-sensitive, too. Lovely boats, mind you, but you can't collect beach rocks on your travels and expect performance to go unaffected.

[Dan McCosh]

This was about light and lean. A PDQ 34 has an amazing amount of room, does 14 knots at less than 4 gph. The beam is 16 ft. big but not ridiculous. Its the overall efficiency that is impressive. Actually, I don't think power cats are as affected by weights as sail cats.

[Dale R. Hamilton]

Seafox- Dale here. Realize you can find boats more efficient, more seaworthy, more livable, more economical, etc- but the trawler is the best compromise(in my mind). And specifically we wanted a steel (sorry), full displacement, robust hull that could be driven 8-10 kts on 140 hp or so, and be safe in rough sea conditions. Maybe one more- but very important reason- it had to be salty. George Buehler's duck seems to be best choice so far. Check out www.dieselducks.com and let me know what you think.

[mmd]

Dan, you are right, but it a matter of degree. A powercat usually has a broader individual hull beam to allow interior volume for bigger engines and great fuel capacity, and broader hull beam equates to greater tons-per-inch-immersion (TPI), which is a measure of load-carrying ability. Also, narrower hull beam is related to propulsive efficiency which is a big deal in sailboats, but in a powercat if you introduce extra drag by going beamier, you just add more horsepower to compensate. Some powercats have hull configurations to allow semi-planing speeds, which requires relatively big horsepower.

In other words (my favourite phrase) - "It depends!"

[Dan McCosh]

Curious as to why the beam of a cat would affect drag. The hulls would be the same proportions, of course.

[Alan D. Hyde]

Dan, I suspect he was referring to the beam of each individual hull, not to the catamaran's overall beam...

Alan

P.S. For the same given individual hull beams, I would expect the wider cat would have less drag (AOTBE), since there would be less mutual wave interference between the two hulls. Or, I am wrong in this surmise, Michael?

[mmd]

Alan, spot on in your first statement, generally sorta right on your second, though it gets a bit murky to try to hang specifics on the hydrodynamics of cat hulls in general.

[seafox]

Mr Hamilton
sorry about mis spelling your name when I first started this thread. I have corected that ( I hope) That was a pleasent couple of hours reading the diesel ducks link. I have greatly enjoyed Mr Bhulers writings and admire his work.
One think I noted is that between the origional 48 which sat 3 inches low and the evolution is that he added 3 tons of displacement yet noted that the dry displacement went from 58,100 pounds up 13,900 pounds to 72,000 pounds. where did the extra 8000 pounds come from?
the speed/fuil calculations are really neat at 7.44 knots he calculates the usage of under 14 horse power and that gives better than a 45 day cruising range on 900 gallons of diesel, (heart attack= $better than 2,000 dollers) well your getting 4 miles to the doller or 8 miles to the gallon not much worse than my car delivering the news papers < G > and to get another knot the horse power needed rises to near 40 and the range drops from 8147 to 3298 n-miles.
You mentioned putting in the 140 horse yet he specifies a 110 hp john deere I wonder is the smaller engine would be significently lower cost? then again if the crusing speeds of 7.44 needed 13.7 horse and 8.1 nots needed just under 22 then why not settle for a 24 horse diesel or would the aditional reduction gear and shorter life running it at ful speed negate any savings?
one other thing is that to get from 8.8 to 9.0 knots ( ie to go from 1.3 times the square root of the waterline length to 1.34 the standard hull speed) would require going from using 39.7 to 72 horse power. the standard I have read is that a gallon of diesel will give 18 horse for one hour Mr Bhulers figures are calculating a power of 16.6 horse, using his figure you would be using 4.3 gallons an hour at hull speed while slowing down to aknot and a half slower your fuil usage would drop to .82 gallons per hour.
you mentioned wanting to go from 8 to 10 knots. can this hull, 46 foot on the waterline be driven at 10 knots?
mostly thinking out lould above. I have thought a lot on building "Bolger box type" craft of 72 feet to be powered by a 10 horse gas engine, though logically I could buy an old diesel rabbit and take the engine out for nearly the same cost ( especally if I could find one that had been rear ended and totaled) I projected a 5 ton loaded weight and if it were slim enough it might achive ( acording to jones of new jersey) 2.2 times the square route of the length waterline on 1 horse per 1000 pounds or around 18 knots this craft of 72 feet by a beam of 8 feet would have a draft of just about 5 inches compaired to the 5 foot 6 of the diesel duck 48
what do you think of draft?

post edited so I could consult the diesel duck pages with out loosing again what I had written

[ 03-10-2006, 01:39 AM: Message edited by: seafox ]

[Presuming Ed]

Longer, narrow, aluminum, and a lot more expensive.

http://www.setsail.com/dashew/do_paradigm.html

[Stiletto]

The hull on that boat looks like a yacht form to my eye and should be more easily driven than the more voluminus trawler style hence greater economy.
I guess, as always, it does come down to what things are traded off against each other.

[Dale R. Hamilton]

Seafox- I think I'm in error when I said 140 hp- when it was 110. We discussed the difference, and George said the 140 would cost more fuel without increase in hull speed. Also the extra displacement you commented on- Bill Kimley has been adding a redesigned cockpit/swim platform thing that looks really good, very practical, but undoubtedly adds displacement. Bet this is the difference.

What about "salty"- you didn't say.

[Ian McColgin]

I was idling along thinking about David Gerr's designs and dropping about sites like
http://www.marinearchitecture.com/fo...ead.php?t=5073
when it occurred to me that many of the folk speculating have not experienced, may not even plan, to live aboard.

I in general am partial to well designed boats. I've last been in the epitome of a long and skinny and may next be in a 1:2. As I mentioned earlier, long and skinny can be either heavy or light - you can get liveaboard displacement on a slender beam if you go long enough.

I did not go into how the superhot needle boats, like the fast patrol boat, are really designed for wave piercing planing speeds and their engines are rarely suitable for noodling along at subsonic speed. The fast boats do not have good sterns for slow speed economy and they tend to have fussier to build step bottoms and other go-fast cool stuff. So, besides heavy or light, you must determine fast or dignified.

You can get a good displacement cruiser that's long and narrow and very economical at under 10 knots.

This boat will still be difficult for many to handle in close maneuver and expensive to dock, haul or do anything where they charge by the foot.

But one other potential disadvantage/trade-off is in the shape of your floor space.

Narrow boats are linear. This can be very nice for easy privacy and certainly an advantage in that you'll not get tossed too far in a cross-sea. It can be not so wonderful if you like sociable accommodation or don't like to burrow too far along just to get something.

It's all in choices and planning and preferences.

[P.I. Stazzer-Newt]

There is some strange stuff - "Out There"
A Catfisher 32


From the side it looks a little like a Scottish East Coast fishing boat.

Here is the Fisher 37 mono for comparison.

[Phil Heffernan]

Hi Dale

I'm quite fond of the Duck as well. You might take a look at this website about his whole construction adventure and launch of the Makena, a 48' DD...

The boat has been cruising for the last 3 years (worked out all of the bugs, no doubt), and a family shift necessitates it's sale...

http://www.cadwell.net/Makena.htm

Might be just the boat your looking for. I found the link in my own research of the Duck, and corresponded with the owner over the DD experience...

He recently let me know it was up for sale, but college expenses preclude my footloose fantasies...

PH

PS, that's actually Jr. High School expense...I'm screwed down for awhile.

[ 03-16-2006, 10:24 PM: Message edited by: Phil Heffernan ]