Conversion from trailer-sailer to low power motor boat

Not to mention gets you out of the boat's butt, making trim issues easier to address.

 

I've been saving a 2 cylinder wisconsin gasoline/kerosene engine (about 18 hp) to plant in a sound sailboat hull as an inboard - making a funky sort of pilot-house "cruiser" - something about 21 feet. Of course old hulls are more or less free. Yes, sailboats can be pretty stiff without their rigging, but many of the day-sailer hulls look suitable to me, and might even plane in a flat out emergency full-power mode. I expect to have to do some stability calculations and 'sperimentin'....and add some steel bedded in seak-a-flex to protect the shaft/prop. Had anybody seen any examples - I'd like to crib from their good ideas and avoid their mistakes...

 

I've been reading up on this subject for quite a while. Some thoughts - Everyone knows that work/fishing boats called "trawler" or dragger or dogger or smack - all these types, began as sail designs of modest size. They were converted to steam and motor power (and began to grow!) at the close of the 19th century, although conversion of fish boats from outboard/sail to inboard petter type diesels continues today in the third world fishing fleets of small boats. In trawlers, the low speed sail type hull remains in modified form - recognizable at least as a descendant of sail. Converting an old mac or venture hull or whatever to a "terminal trawler" is more practical now than it was in 1912 - 100 years ago. What you get is slow and cheap to run. Yes, the boats tend to be uncomfortable with respect to ride, but a careful attention to (and competent calculation of) stability and roll-damping (proper ballasting and bilge keels), and keeping a bit of sail, can result in a low-cost and fun boat. Direct drive inboard engines are around and the diesels (listeroid and petter types with compression release) can (check the oil pump design!) be spun in reverse with prestolite electric reversible motors - giving approximately the functionality of a direct-reversing engine, sort of (at least long enough to maneuver out of a slip). No quick reversing, though, takes a while to stop and reverse such engines even if there's a flywheel brake. Sure, a transmission is better. But not essential. It's my intent to build something along these lines with a center pilothouse and a 650 rpm diesel engine. Collecting the stuff... The Lister makes 6 hp@ 650 revs and uses about 1 gallon per 4 hours. Don't use it much anymore and planning to pull it out of my generator shack when we move.) I remember seeing working small trawlers as a child - and it makes me want to build my own. Go figure!

 

I know you said you wanted to go up a bit in hp, but I thought I would just throw out the idea of a propane outboard. I've heard sailors love them because there are hardly any emissions and they are virtually matinance free. I've seen a 5hp I'm not sure if they make any larger ones.

 

i have seen diesel outboards, and kerosene, but propane is something new to me. I believe I'd be concerned about fire dangers and fuel consumption - lp, being introduced as a gas displaces air and has the effect of lowering both compression ratio and power output. being a heaver-than-air gas at stp it seems like a problematic fuel for a decked-over boat.

 

I haven't seen the propane outboard in action but I heard you can run it 10 hours on a 20lb tank of propane which is actually pretty cheap.

 

Well, let's see...20# of LP is about 4.7 gallons, and over ten hours that's an average consumption of 0.47 gallons or just under 2 lbs per hour. Colorado State (http://www.ext.colostate.edu/pubs/farmmgt/05006.html) says 0.080 gallons of LP gives (in the real world of farm and dirt) one horsepower for one hour. Let's assume a "5 HP" 4 stroke motor (I guess it could be done with a 2 stroke, but it'd be tough) so, 5 x .08 = 0.4 (gallons). Yup, it's a credible claim. I don't see any advantage, but, well, at a marina where the propane'd be free for the management it'd maybe be worth the trouble to use a propane outboard for the work-boat-skiff.

 

Paper dealing with fuel consumption (and more) of outboards and petter diesels in work-boats http://tinyurl.com/cpm39ca

 

I like your Terminal Trawler! Another nic-name is "Strawler", an interesting article about a guy mear St. Charles, Mo. converting a Mac 21/22 as an ideal river cruiser. Also suggested as a Looper, to do the Great Loop for the hardy at heart. Sorry I don't have a link, google will get you there.

As to your boat, I'd fabricate a windshield, may be a fold down. I'd have go to a boat cover shop and the can probably make side and rear curtians for a camper enclosure much like those on larger cruisers. Zip roll up vinal for windows and they can put in the screens as well. I had one made for a 26' cruiser out of Hypolan (sp?) and it was great! In fact, I might keep your top and just have a camper top made to match on such a nice boat.

Around here, PVC pipe, a hose and hose clamps make an extension pretty easily.

I'm seriously considering a Strawler as well! I'm on the trail of an older 40' Willard pilothouse built for the Navy as a liveaboard, it will carry a washer and dryer and my cargo needs. But, if it doesn't turn out I'll be looking for a 24 to 30 footer for a conversion.

The Strawler article featured another guy who converted a much larger sailboat, like 46' I think, making a very nice pilothouse strawler. He trimmed off the keel and added cement for balast. While I'm sure he has money tied up in his conversion it would probably take over a hundred thousand to duplicate what he has above the water line with a conventional trawler.

Great to see so much interest here on such a conversion!

 

The classical "Monterrey Clippers", similar boats, tended to chose the "frisco" engine in the 8 hp version - a compromise. But their experience tells us how much engine a terminal trawler needs, more or less.

I knew a couple who built a riverboat/canalboat along these lines - communists, they lived in Czechoslovakia. (Guy works in a bank now, he burned his boat when he decided to leave communism...well, he couldn't take his boat with him...) They say it was difficult doing boat-building in a country with a centralized communist economy. their coolingwater pump, for example, was the fuel transfer pump from a Dakota, a DC-3, probably a stolen pump. But it was neat too, they said, because you didn't worry about buying diesel - (they used a VW diesel motor) - anyway, in commie countries of eastern and central europe, one packed aboard cases of home-made vodka, not money (nothing to buy with it) or fuel. Then, each river-evening (or canalboat evening) they'd side-tie to a state-owned barge (they were all state owned barges) and smoke cigarettes and chat, the girls'd smile, and the vodka'd come out. By morning the hose had come out and the communist fuel had drained from the state barge into the "terminal trawler". The rate of exchange? About 5 gallons of fuel for a quart of vodka... Not so bad. Machine parts in general were obtained the same way - you knew a guy who would do a "g-job" - make the parts at his state job - and he'd do that for vodka. Engines were cheap too - as the state said that body and engine numbers had to match, so there was zero value for a used engine from a wreck. Again, a quart bottle would buy just about any motor. Of course, this was Czechoslovakia and East Germany and so forth. Things may have been much less accommodating as one moved east... Anyway, my old pal took pictures of his burning boat. I've seen 'em.

 

Trading commodities was common through out Europe I'm sure, I paid much of my penthouse apartment rents 40 years ago with Jim Beam in West Germany!

I'm insisting on a smaller power plant, gas or diesel, I looked into propane and like you said Larry, loss of power, cleaner but it has more of the boom factor when it comes to storage, overall not a good idea in a decked boat.

For a strawler, TT, I'd rather go with a 4 stroke OB.

You'all think a trolling motor with an extension would help in the dock areas for a bow thruster on a 30'er? I've never tried turning a 30'er in it's own foot print with a small OB.... ?

 

If somebody said that working for the us army was a lot like the tales about Czechoslovakia they might be right. There were many "g-jobs", and many of the machinists had boats. I seem to remember people making titanium parts for their own and their friends "projects". I even remember stories about liberation of gasoline, gasp!

One guy, it was said, even built boat trailers at work...for a while.

And in Korea, back in the day, the girls were one case, two case, and for the top shelf - 3-case girls. Case? Jack Daniels. The old stories about cuba and gitmo are too dark for this arena...and the men and the girls and the kids - all grown, gone. Does anybody remember the narrow gauge railroad at gitmo?

Nominal 10 hp 4-stroke OB would, I should think, be fine. Yet my own opinion is that the prop size/rpm is going to make a very poor coupling or match with a hull that measures 20 to 30 feet. Worse, the OB is going to be temperamental as it ages, and, in a difficult weather situation, is liable to fail. My esthetic sense says slow inboard <20 hp, direct or gear-reduction, 12 " prop (or bigger). There are numerous industrial engines that might be "marinized" to suit the job. I'd favor air-cooled for simplicity...kitchen rudder or transmission. Given that the kitchen design works really well <10 kts that'd probably be best - as these boats are not going to be fast at all.

I have experimented with bilge and stem keels, wings more properly, that have aspect ratios and area that can be exploited to achieve considerable maneuverability - similar to thruster effects. The method was to mount a single large high-aspect fin about 1/4 of WL from cutwater on the keel-line, and mount a pair of low aspect ratio fins parallel aft, under engine, perhaps 3 feet from transom. With that arrangement the boat (32' steel with 100 hp ford) would turn 180 at full speed so quickly that the boat was making stern-way, yet was so solid in terms of heading that I could go below briefly to re-fill my coffee cup. At low speed the aft fins had almost no effect. As speed increased the boat tended to lock onto a course. It was an (eaton model B) outdrive boat.

I toyed with the idea of making the fwd fin steer-able. Didn't do it. Similarly, toyed with the idea of a jet-thruster ... the idea being an electric pump with valves and two jets. One jet left, one jet right; all mounted under the fo'c'sle deck.

g'nite.

 

terminal trawler... completed

I have finally completed rebuilding one of these myself after reading this forum a while ago... worked out well and saved a boat from going to the dump.
EX Noelex 22

 

ooops

Sorry, i'll try that again

 

Looks good to me... congrats on getting it done. Do you have any pic's you took while working on it, or a blog somewhere, or....?