Compass 38 hp requirements

[chphotographic]

HI,

Looking at a compass 38-- Same mold as a Pacific 38.

So.... It has a "new" Vitus 28Hp engine in it. They originally had Perkins 4-108s.

I think that the 28hp will be underpowered.

Which to me means higher fuel consumption because of high RPMs, and more importantly no reserve power available when you need some spunk to get out of trouble.

thoughts?

FYI:
This boat will be for cruising equatorial Asia/pacific with 2 people and arguably too much stuff, we like to sail, but we are not above using the diesel breeze to get us where we want to go when we want to get there....

Hull Type: Fin with rudder on skeg
Rig Type: Masthead Sloop,
LOA: 38.06' / 11.60m,
Beam: 10.50' / 3.20m
Listed SA: 590 ft2 / 54.81 m2
Draft (max.) 6.00' / 1.83m Draft (min.)
Displacement: 16640 lbs./ 7548 kgs.
Ballast: 7280 lbs. / 3302 kgs.
Sail Area/Disp.1: 14.54
Bal./Disp.: 43.75%)

[Cheechako]

Does sound a bit underpowered.... but my heavy Hans Christian 38 had a Yanmar ... 3YM30 I think... maybe it ws 3QM30 actually... not sure if it was actually 30 hp or not.... and was underpowered. In flat water fine, In a chop.. not fine. It could be useable though... sounds like it would have a lot more power/weight than the HC did.
I think some Vetus are hell for parts too, how old is it? model? Misubishi?

[chphotographic]

It is supposedly a new Vetus M.328 with 10 hours.

[DougR]

This looks like a fairly low drag hull, certainly better than the HC 38 and you will probably be fine with the 28 h.p.

The vessel displaces just a bit more than 7500 kg. or 7.5 metric tons, so that's about 4 h.p. per ton and that should be plenty to push that boat.

The question that comes to my mind is whether it's possible to fit an adequate size prop in the available aperture. As long as it's possible to get a 16 or 17 inch prop fitted, a three blade prop should push the boat fine.

Take it for a sea trial and see what it does...

DougR

[chphotographic]

Any compass 38 owners out their???

[donradcliffe]

The 4108 that was replaced only had about 35 useable hp. You will be fine unless you want to motor into a strong wind and chop. For normal use, the smaller hp engine will be more efficient. Normal rule of thumb for repowering used to be 2 hp for every 1000 lbs displacment. The new engine is 15% less than that but it should be fine in the light winds of the equatorial regions.

[chphotographic]

Found this on another thread (see below) I have experienced very strong currents in the area I will be sailing (and no wind too) and don't what to get called out.....

As said, sea trial is the only way to know...

Until then anyone with a compass out there I want to be convinced 28hp is or is not enough before I fly to see this boat..... and I really want to go see this boat!

Not against a repower, but my estimated refit cost keeps getting bigger and bigger-- I just want to go cruising!

Originally Posted by GordMay

The rough Rule of thumb for determining Horsepower Required for a Sailboat : one horsepower per 500 pounds ( ± 50lbs ) loaded.

Expect you'll want a lot more than 28 HP (> 55 HP).

PS:
Just came accross this in my files:

Westerbeke Corporation suggests 2 hp for every 1,000 lb of displacement for coastal cruising, and 2.5 hp per 1,000 lb of displacement for offshore. That would mean a 38 ft. sailboat with a displacement of 15,000 lb should have a 30 hp engine for coastal cruising and a 37.5 hp engine for offshore.
In your case: 15 Long Tons = 33600#
Hence: 33. x 2 = 67.2 HP ~or~ 33.6 x 2.5 = 84 HP.

In their book "The Gougeon Brothers on Boat Construction" the authors suggest a good rule-of-thumb is 1 hp for every 500 lb of displacement... that would mean 38 ft. sailboat with a displacement of 15,000 lb should have a 30 hp engine.
In your case 33 x 2 = 66 HP

Some people suggest 1 hp for every ft. of boat waterline length... that would mean a 38 ft sailboat with a waterline length of 30 ft should have a 30 hp engine.
In your case 41 x1 = 41 HP

Some people suggest 3 - 5 hp (continuous rating) per long ton (to calculate the boat's weight in long tons divide the displacement by 2,240)... that would mean a boat with a displacement of 15,000 lb should have a 20 - 33 hp engine. For offshore conditions some people suggest the engine be larger than the size calculated for coastal cruising, possibly + 25%... so in this example the engine size would be increased to 25 - 41 hp respectively.
In your case up to 5 x 15 = 45 HP

How do you measure horsepower?
Power is a measurement of the ability to do a unit of work in a specific time. It is calculated, not measured. Horsepower and watts (kilowatts are 1,000s of watts) are units of power. Power is calculated by measuring engine torque at a specific crankshaft rpm and multiplying the 2 figures together.

Engine Horsepower/Torque Formulae

Horsepower = ( Torque in Lb/Ft x Crankshaft Speed in RPM ) ÷ 5252

Power = Torque X RPM
Torque = Power ÷ RPM
RPM = Power ÷ Torque

[donradcliffe]

Play around with

Boat Speed Calculator

My guess is that with your boat in flat water the difference between 28 and 38 hp will be about 0.5 knots.

[Cheechako]

In flat water a 10 hp outboard will likely get it near hull speed. It doesn't take much. What matters is when it gets choppy...

[rmesfo]

Originally Posted by chphotographic

HI,

Looking at a compass 38-- Same mold as a Pacific 38.

So.... It has a "new" Vitus 28Hp engine in it. They originally had Perkins 4-108s.

I think that the 28hp will be underpowered.

Which to me means higher fuel consumption because of high RPMs, and more importantly no reserve power available when you need some spunk to get out of trouble.

thoughts?

FYI:
This boat will be for cruising equatorial Asia/pacific with 2 people and arguably too much stuff, we like to sail, but we are not above using the diesel breeze to get us where we want to go when we want to get there....

Hull Type: Fin with rudder on skeg
Rig Type: Masthead Sloop,
LOA: 38.06' / 11.60m,
Beam: 10.50' / 3.20m
Listed SA: 590 ft2 / 54.81 m2
Draft (max.) 6.00' / 1.83m Draft (min.)
Displacement: 16640 lbs./ 7548 kgs.
Ballast: 7280 lbs. / 3302 kgs.
Sail Area/Disp.1: 14.54
Bal./Disp.: 43.75%)

I passed on a really nice Morgan Marek 454 due to the 27hp diesel. Not enough when you need it.

[Mike Banks]

I do not think it is enough power. I would prefer forty horse power. Most of the time you will be sailing, but when you need horsepower you will not have it with the current engine, as has been said when facing a severe chop and a headwind on the only possible course to safe haven..

[Yoty]

Our old salts at the bar reckon take your age, double it and there's your horsepower requirement. I'm old enough to consider it.
My 3 Mtr Hal Wagstaff Moth won't like 76 hp sitting amidships.
I forsee great difficulty righting the yacht after a capsize.

[Djarraluda]

The old adage from back in my younger days in Pommyland - 1HP per foot !
Problem is, no b.... ever specified if that was OA or WL. Ah well, can not have it all I suppose.
As a recent Compass owner, a 28 not a 38, was the 8HP was adequate for the 28 until it blew a bit, or there was any fouling on the prop. 14HP would have been ample and is the feeling that most 28 owners get when talking on the forum. No 38 members appear on the forum, so it is not worth consulting there as it is Geoff and myself who comment a lot.
Seriously though, my experience would say that it is currently marginal, fine for local sailing, but serious passage making can encounter some interesting events where you would appreciate the extra grunt.
Worth purchasing an Autoprop, Absolutely, it will enable you to maximise what performance you have.
Worth dumping an almost new engine........... I would not be courageous enough to offer that advice, but presuming the answer is a No, then use your seamanship to avoid the nasty times. Choice of anchors and chain, location of anchorages, watching of weather patterns and willingness to spend extra days at sea because you may not be able to make that harbour.
Roger

[Dash-Robo]

Drive Shaft restrictions
Guys some great information But every engine choice will be limited by a 25mm drive shaft and limited prop size of 16 to 17 inch
I have an Olympic 40 compass 38 hull Ben Lexcen Deck great sea going hull proven over many years originally fitted with a 28hp engine i am the third owner and third repower replaced volvo 4m40(perkins engine rebadged)with a Vetus 455 turbo 52hp.
Similar Foot print so an easy fit,same weight
Positives great performance able to make 9 knots @2800 ,6 knots at 1600 rmp great fuel consumption in right conditions
Negatives increased prop walk forward and reverse will take some getting used to

[chphotographic]

Great info Dash-Robo,

I have been looking in to re-power options. I am keen on the Bata 38 right now, but I have always seen value in having more hoarse power up your sleeve should the need arise. I will look into the Vetus 455, their is a Vetus dealer near the boat, and I assume switching out with another Vetus would simplify things to some degree.