Trawler Concept

[mackid068]

Hi all! I have a trawler concept in mind. It is a Nordhaven-esque trawler intended to have light to moderate passagemaking (only to Maine and back from Long Island Sound) capability. It WILL NOT, NOT, NOT look like, in the words of eminent yacht designer Ted Brewer, a "rocketship." My intention is to have it look good for as many years as it can, give it a modern touch on a classic look. It's specs are as follows:

LOA: 32 ft.
LWL: I'm not sure but probably 30 ft.
Beam at Widest: 12 ft. (Maybe 14')
Displacement: Not sure how to figure this out
Hull: Full (heavy) displacement, full keel, double hulled fiberglass with composite reeinforcements or single layered steel
Powering: Diesel: 32 b.h.p. (if this is enough?)
Rudder: Probably doublehung with a large aperture.
Drawings to come!

My questions:
1. Is 32 b.h.p enough for a boat of this size?
2. How do I figure out displacement?
3. Anyone have any drawings to aid me?
4. Full keel...is it a good idea?
5. Is a 12-14 foot beam ok for stability (I want to have a stable boat even at the cost of speed)
6. What is a reasonable speed? How about 10-12 kts?
7. Does anyone have any engineering/safety problems with aft house (no open deck on top of it)?
8. Anything else?

Essentially, this design is intended to be an anti-rocket ship boat for the rocketeers.

(Rocket ship/rocketship=Eurostyled boat)

PLEASE RESPOND EVEN WITH IDEAS, ADDITIONS ETC FOR ANY ASPECT OF SUCH A BOAT!

[fcfc]

D/L ration = (D/2240) / ((L/100)^3)

D displacement in lbs. L length in feet.

D/L under 100 = ultralight.

D/L over 300 = heavy.

a D/L around 200 gives you about 15000 lbs displacement for a 32 ft boat.

hull speed = 1.34 sqrt (LWL).
7.3 kts for a 30 ft lwl.

So at 12 kts, you are on the start of planning.

132 hp should be better than 32 hp (one hundred more,perhaps even more).

nordhavn (except the 35) are all limited to hull speed.
The 35 is semi planning, but it has more than twice the power of the 40 and weigths less than half.

[yipster]

Essentially, this design is intended to be an anti-rocket ship boat for the rocketeers. (Rocket ship/rocketship=Eurostyled boat)
mackid068: i live in europe and like rocketships, dont hurt me please.

for your questions i suggest a couple of searches (button above) to get some basics.
you can also visit trawler sites, check / compare specs etc.
good luck with your anti-rocket ship boat

[mackid068]

Thanks very much. Oh, by the way, I love Europe, despite the fact that I live in a warmongering nation.

[Doug Lord]

Why not consider a power cat? There are already some power cat designs with a "traditional" appearance....Could achieve the speed you want at very low power compared to a heavy displ. monohull.

[mackid068]

Hmmm...I dunno, but if you could find some websites or names then I could look up this information. Also, from an ease of use standpoint-even with bowthrusters (are they on cats?), cats are probably hard to dock even in a moderately confined area. Also, I'd like to limit costs as much as possible, so a cat is unlikely, but perhaps, if I am convinced, I'd give it a try.

[Doug Lord]

068, see the April/May issue of Professional Boatbuilder and /or check out:
http://www.chriswhitedesigns.com The boat featured is not a trawler yacht but illustrates Chris Whites belief in displacement power cats having speed(30knots on a 32' X 12.3') and efficiency.
The boat is the Buzzards Bay32cwd built to a Chris White design by Multihull Development ( http://www.mdcats.com )
And there are many other builders of power cats-both displacement and planing- you can find with some research.

[mackid068]

Thanks for the link. I really do like the style of the Buzzard's. Nice, traditional yet modern.

[PowerTech]

essentially devoid of all culture :?: That is not true.

[FAST FRED]

"I love Europe, despite the fact that I live in a warmongering nation essentially devoid of all culture."

The Culture of the USA is what allows imbeciles a computer.

Having spent lots of bucks in the last century to FREE over a billion folks should be enough Culture, The Culture of Liberty!

If you prefer the culture of License , Ill get the 1 WAY ticket to Eurowimpland for ya!

Good riddance to ignorant trash,

FAST FRED
__________________

[mackid068]

Trash? Hah. I don't wish to annoy anyone, but I dislike the current administration. I thought that was clear. By the way, the United States is better in many respects:

1. Tax system (though it needs alot of help)
2. Written Constitution (unlike much of the world)
3. Bill of Rights (needs improvements, but it's pretty darn good)
4. Last but not least, the United States Navy and USCG!

[PowerTech]

Wanabe :rolleyes:

[mackid068]

Sorry? Please elaborate. Oh and by the way, how much diesel power is needed for a full keel, full displacement hull boat with a displacement of 15000 lbs. (As I see, PowerTech, you are a marine diesel mechanic and I thought you could offer some sort of insight)?

[clearwaters]

I second the one way concept Fred. But 12 kts on 32 hp not bad. Learning to face up to the real world and find it takes horsepower to go fast. Let alone lots of cash for the fuel. GS

[fcfc]

What my own spredsheet gives for 30 fr LWL, 15000 lbs

D/L = 250
Hull speed = 7.33 kts
Max displacement speed = 8.14 kts

7 kts = 18 hp
7.5 kts = 22 hp
8 kts = 28 hp
9 kts = 39 hp
10 kts = 55 hp

This mirror like water, clean hull and prop, no wind. (theorical conditions).
Safe to at least double for non theorical for wind, waves. Even more if you want to go winward in 30 kt wind and associed sea state.

Efficiency propulsion assumed 50%. not exceptionnal, but correctly designed propulsion system.

The boat weigth is ready to sail weigth. (crew, filled tanks, gear etc ...)
for info, 9 kts @ 20000 lbs need 52 hp.

[fcfc]

BTW, look at Grand banks 32. It has been in production for 27 years, since 1965. Its clones, Integrity/island gypsy 32, are still in production.

So this boat should not be too far from truth ...

The main problem seems to be a lack of speed, since power evolved from 78 hp to 210 hp in 30 years. And some even got 2 * 200 hp.

[FAST FRED]

Grand banks 32.

With only 32 ft of boat speed is not in the offing.

6k is about all most folks will put up with in terms of noise , RRPM , and fuel use for this style full displacement boat.

FAST FRED

[clearwaters]

I checked my spreadsheet this morning, and i agree with the specs.

SL 1.34 7.34Kts 21.5 HP DL248 15000lbs
SL 1.4 7.67Kts 25.74 hp 30LWL
SL 1.5 8.2 Kts 33.10 hp

So this nice light weight hull will be fine at speeds around hull speed. But when you get much faster the HP requirement will go up drastic. Hench the early post of 134 hp will be more correct for the 12 knots. My spread sheet i made after talking to Robert Beebe to get some of his formulas. The next time i called his wife said he had passed away. She said he got to make a last cruise and enjoyed it very much. GS

[fcfc]

Form MikeD displacement / semi displacement spreadsheet:
(more elaborate than mine)


figures for Shaft horsepower. (ie at the propeller)
For engine power, add 1.5 for each shaft bearing, 2.5 % for gearbox and 2.5% for error. So a total of 8 %.

No wind condition:

7.150 kts 19.6 hp
8.46 kts 36.8 hp
9.77 kts 56 hp
11.1 80 hp
12.3 kts 108 hp

with 30 kts wind

4.5 kts 34 hp
5.8 kts 50 hp
7.150 kts 73 hp
8.46 kts 102 hp

for info, 8.46 kts with 15 kts wind need 57 hp.

I have found MikeD spreadsheet on this forum, but I do not remeber where. You will have to do a search.

[mackid068]

Thanks guys. I appreciate all your help. I think I'll do semi-disp with a 150 b.h.p. diesel.

[fcfc]

Has someone some figures for the GB 32 ?

the figures I have gice 7.5 kts @1800, 8.7@2300 , 120 hp engine.
other give 7.4@2000, 8.5@2400, 135 hp engine.

But MikeD spreadsheet gives over 11 kts with only 110 hp. including losses.

Why so many difference ?

BTW, 8.5 kts for a 16hp/ton boat is rather low.


Thanks.

[MrYagci]

If you are interested, I have got a newly finished design of a 14,4m. Oceon-going trawler which will be build for a german guy. If you want to built the boat I may help :)

[mackid068]

It's design now, but building is probably not in the works...lack of $....