15 m (50') semiplanning boats

Rangeboat

40, 46, 56 feet versions of this hull seem to be planned.

This is information only feel free to design your own.

http://www.nigelirens.demon.co.uk/FRAMElaunch.htm

 

Thanks Tad and Jorg. Also to PAR for the PM.

Cheers.

 

I have the plans for STROLLER , from the MIT museum . but they have no performance information.

The concept is right ,long lean and as light as can be rationally be built for rough service.

The wood construction could be probably half the weight today and new diesels (if you are willing to go offshore with converted car engines) are far lighter for the power. Less fuel would need to be lugged with the same range.

The Lake Powell (sp?) boats have the same good looks with the 20's or 30's retro look.

Probably a 5-1 LB is as fat as I would dare and hope for any efficency at speed.

FF

 

Guillermo,

Way too fast, way too beautiful and way too costly, but it's a lobster boat.

http://www.vicemyacht.com/

Perry

 

Thanks, Perry and Fred.

Happy New Year to all!

 

AS the higher speeds would be "get home Quick" only , I think a seakindly round bottom would be the best choice.

No extra stability would be gained from flat spots in the stern , but the better rough water ride at all times should make up for that.

FF

 

Guillermo,
I'm not sure of your meaning with the use in your first post of the word "trawl"? On this coast trawling is a fishing method using a towed bag shaped net held open under water by "doors". These nets are set on long towing wires, from large drum winches, and are very heavy loads. The boats are called trawlers or draggers and are equipped with powerful engines. I don't think that is what you are after.

On the other hand (and again on this coast) trolling refers to another fishing method where individual lines with hooks and bait are towed through the water at a low speed, usually 1-2 knots for salmon but faster if fishing for something like Tuna.

Or perhaps your use of the word trawl just refers to slow cruising?

Pericles,
The Vicem is many things but it's no lobster boat....this is a lobster boat.

Lobster boats are characterized by huge open flush decks for carrying lobster pots. They have an open control and pot hauling station forward on the starboard side. The hulls are designed for speed, this 36' is powered by a 325HP Cat and runs over 20 knots. 42' s are set up with 5-600HP.

Not sure what Fred is getting at...
At 7 knots the round bottom hull will have the lowest resistance, it may roll more or less than any other shape as there are other factors involved. At 14-15 knots dynamic stability comes into play and the boat could benefit from "flat spots". Also at this 15 knt speed (and no matter the form) a flat spot in the form of a spray strake or chine will be required forward.

A 50' hull at 7 knots is S/L of 1.01, which could be very efficient if the hull is formed to take advantage of this low speed/length ratio. But a 50' hull at 15 knots is a S/L of 2.1, well up into semi-planing territory. There will need to be a large compromise at one end of the scale if you want optimum efficiency at the other end. Or you can design around an 11 knot speed, S/L 1.55, and compromise somewhat at either extreme.

If the hull is formed and powered to run nicely at 15 knots, you will pay a penalty at lower speeds, partialy from high resistance and partially from too much HP. If she is designed to run nicely (level with low resistance) at 7 knots, trim (and drag) will be excessive at 15 knots.

What you need is a variable form afterbody, and triple engines could be very efficient except in first cost.

Tad

 

Tad,
what I really mean is 'trolling', of course. An stupid mistake from my bad english.

I had done a first rough estimative, and for 45' Lwl and 12' Bwl with a displacement of 30,000 pounds at 70% load, we'd need around 240 SHP for 14 knots.

I'm considering now also to reduce top speed to around 12 kn, where power needed could be only of around 150 SHP. I'm thinking about designing for efficiency at this performance, as we'd need only about 32 SHP for trolling at 7 kn.

But it's soon yet to make decissions. More thinking around is needed.

All the best.

 

whalingsloops once were fast, sloops are popular here and i've seen weird wing fixtures on the skeg to get them up over the hump

 

Tad,

Thanks for the guidance and the picture When Guillermo gets to his office tomorrow he'll have to plough through my email to him listing a large number of sites relating to trawling, when he meant trolling. Oh well!

Al the best,

Pericles

 

For 15m, less than 300 hp, you had once the Grand Banks 48 http://www.gbwoodies.com/member_site.php?id=210 with twin lehman 120 hp.
The very early krogen express 49 http://www.yachtworld.fr/boats/1813877/0/ with twin 170 hp.

Sligthly heavier and slower the selene 50 http://www.fridayharboryachts.com/selene/s50/s50.html


But all are no longer in production. The current GB 47 has now twin 593 hp, the current Krogen express 52 has twin 480 hp. and the selene has increased to 53 ft.


Line drawing of the krogen express 49 can be seen there http://www.yachtworld.fr/boats/1710990/0/ But it is already an evolution of the initial design. The initial design had 170 hp engines under the salon floor and a third cabin under the pilotehouse (portligths in the hull) . Very quickly, the engines had been increased to 420 hp, and used the space below the pilothouse because they no longer fit under the salon floor. BTW, engines hours of the ads show that owners of such boats run engines between 75 to 140 hours a year. The yearly fuel bill is about 2% of the boat price given twin 420 hp used at 60% average power for 100 hours.


Homebuilt way is http://www.glen-l.com/designs/cruiser/klondike.html


I fear that if you want to reduce speed for money reasons, to cut costs on fuel, you are on the wrong path.

Seems that the best way to reduce ownership costs is to reduce length, not speed.

You 15m semidisplacement will have to face competition from 12m planning hull like
http://www.grandbanks.com/yachts/heritage/41eu/index.cfm , http://www.beneteau.fr/en/motorboats/produit.aspx?GAM_CODE=12&PRO_CODE=56 , http://www.swemarine.com/commander410.html

All are current (and recent ) production from big names (with marketing departments). The initial price tag is between 360 k€ (beneteau) to 600 k€ (swemarine) tax included for new boats. Which is lower than the price tag for a new 15m boat, even semi displacement (guess estimate from 600 k€ to over 1 M€). The asked used price of a 12 years old krogen express 49 without sales taxes is higher than brand new beneteau price including sales taxes.

Maintenance cost will be lower for smaller ligther boats, starting with marina fees or hauling.

And at 14 kts, I am not sure that a 12m 10tons planning hull burn more fuel that a 15m 15tons semi displacement hull. I agree efficiency will be lower due to hull form and shorter lwl, but I am not sure it will be enougth to overcome the displacement difference.

Same, the inside volume is not so much smaller. These 12m planning boats are on the beamy side, higher stacking. (All have top cockpit / flybridge).

And all can go over 25 kts if the owner wants some fun.

 

I think perhaps you could try to contact Stephen Ditmore if you want first hand information on the Krogen Express 49.

http://www.boatdesign.net/forums/showpost.php?p=1254&postcount=13

Also read http://www.kadeykrogen.com/articles/pages/TrueToFormUnedited.htm

So I dont really know where the 2 x 170 hp version come from but it sure does exist, since it is on sale.

 

Thanks fcfc for the nice post and Perry for the extensive list of 'trawlers' I've found at the e-mail (so sorry for my stupid mistake )

fcfc,
fuel bill is not a concern, but keeping power low and traditional appearance is rather a philosophical matter in this case.

Cheers.

 

Guillermo,

Posted elsewhere, a hull form disguised as a Down Easter.

More very useful information about construction is available at http://www.mecat.com/indexpower.htm

The P-45 regular updates for 15th October 2006 reveal an unusual (to me) underwater hull form.

Perry

 

You could look at some of the early "Carolina Fishermen" from the outer banks/Hawkers Island or early Tollycraft or Trumpy designs.

The big question is what do you mean "low powered".

A modern sportfisherman is expected to range 50-100 miles offshore. In order to make it a day trip, sea speeds need to be in the 25 knot range. Additionaly, if you're after billfish, trolling speeds and fighting speeds need to be higher than 7 knots, or the fish may strip the reel in a run.

The older Monterey Clipper trollers, were very low powered, but whet out for days at a time.

Then you could always look at a Wheeler.
http://www.gilligansisle.com/minnow.html