Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 16-01-2016, 00:02   #1
Registered User

Join Date: Dec 2014
Posts: 97
Hp to displacement ratio

I'm currently looking at a 44 foot fibreglass Bruce Roberts design. As with all potential purchases there is something that doesn't excite me. This time it's engine size... it's running g a 49hp yanmar (or about that size I don't have full details at hand). Is this big enough for the displacement... and is there a ratio to work with here?

Sent from my GT-I9506 using Cruisers Sailing Forum mobile app
__________________

__________________
nzmal is offline   Reply With Quote
Old 16-01-2016, 00:14   #2
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2007
Location: Santa Cruz
Boat: Boatless Again
Posts: 4,324
Re: Hp to displacement ratio

2 hp per 1000 lb is typical for a sailboat.
__________________

__________________
donradcliffe is online now   Reply With Quote
Old 16-01-2016, 00:49   #3
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,712
Re: Hp to displacement ratio

Quote:
Originally Posted by donradcliffe View Post
2 hp per 1000 lb is typical for a sailboat.
Second that, 4-5 HP per tonne is generally reckoned to be about right for a sailboat.

If you were looking at a heavy displacement motorsailer, you could possibly double that.

Or if you want to get technical, here's a common formula which also factors in waterline length:

HP = (((DisplacementTonnes*75)*(1.4*(((LWL)^0.5)))*0.00 3)/0.45)
__________________
StuM is offline   Reply With Quote
Old 16-01-2016, 11:00   #4
Registered User

Join Date: Oct 2011
Posts: 2,433
Re: Hp to displacement ratio

Unless you are planning on cruising in areas of very high currents, 49 HP should be fine. Most depends on what you want to do with the boat, and your sailing experience. If you are the type of person that wants to get from point A to point B regardless of weather or sea conditions, then you could do with more HP, but for cruising, 49 HP will do fine. Larger engines mean larger props, which means less performance under sail (unless you have a feathering prop), so you want to think about which is more important to you, sailing or motoring? I cruised a 44 foot, 30,000 lb boat for 8 years with an engine that would overheat if pushed, so I never ran it over 1800 RPM, which is less than 25 HP. It was enough for normal cruising, but going through the Panama Canal, I would have liked to have had more power. A true 49 HP would have been more than enough. I think the big question should be, does the rest of the boat fit your requirements, and does it appeal to your senses? A good survey will let you know the condition (good surveyors are hard to find), and have an engine survey done also. Too many modern sailors will recommend bigger and bigger engines, when a better sailing design and lots of practice sailing is far more important. I just went back and re-read your post, and maybe you could tell us a little about your experience level, and the area you plan on sailing or cruising? As with all things on CF, these are only my opinions. Good luck with whatever boat you decide on. _____Grant.
__________________
gjordan is offline   Reply With Quote
Old 16-01-2016, 14:11   #5
Registered User

Join Date: Dec 2014
Posts: 97
Re: Hp to displacement ratio

Thanks Grant
Here is a brief reply I got from the owner with engine specs and a link to the listing. We're looking for a cruiser to take us around New Zealand and into the Pacific once we have more experience. Current sailing experience has been the typical dingy heritage into 22 foot trailer yacht... so this would be our first keeler.

Hi Malcolm, construction is handlaid grp to Lloyd spec. engine is Yanmar 3jh2-te 46hp turbo with 3000hrs, filters changed every 100hrs. no leaks. over /under v berth fwd then small double aft of that to port and sea berth to stb.dining table with seats fwd/aft on stb side. sea berth on port side in saloon.going aft is galley, fridge then aft cabin. on stb side is radio station, tool locker, then head with bath shower over. has small power survivor watermaker but i never used it so membrane will probably need changing but there are others on board. Sails are 13 years old and in good shape for age, i had main strengthened on luff,leach and reef points. two headsails, two staysails and assymetrical mps in sock.i will replace gas califont( for hot water) when i return to nz, soft dodger* needs replacing but sound boat for ocean passages, simple and strong.
http://www.vinings.co.nz/v/e3e9b64f_...e875f04bb.html


Sent from my GT-I9506 using Cruisers Sailing Forum mobile app
__________________
nzmal is offline   Reply With Quote
Old 16-01-2016, 18:20   #6
Registered User

Join Date: Oct 2011
Posts: 2,433
Re: Hp to displacement ratio

nzmal, That listing looks like a good solid cruising boat. I am not at all familiar with NZ pricing, but it seems a bit pricey to an American. It seems like it has been well prepared and I am impressed with the ground tackle. You will learn that good ground tackle is the best insurance that a cruiser can have. Bolt a windvane on the back and you have a nice simple cruising boat. I had to laugh when you said your experience was a 22 foot trailer sailor, and you are moving up to a 44 foot cruiser. My last boat was a Peterson 44, and just a few hours ago I trailered home my new (to me) 22 foot Catalina. I think you will find that the sailing of the bigger boat wont be too much of a learning experience, other than size and muscle power needed to handle the sails, but learning proper anchoring techniques should be high on your " need to know list". The engine should be just fine if it checks out good after an engine survey. I wish you the best of luck. _____Grant.
__________________
gjordan is offline   Reply With Quote
Old 16-01-2016, 18:57   #7
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,712
Re: Hp to displacement ratio

Quote:
Originally Posted by gjordan View Post
nzmal, That listing looks like a good solid cruising boat. I am not at all familiar with NZ pricing, but it seems a bit pricey to an American.
1 NZD = 0.65USD so that 125,000 is only a bit over 80,000USD
__________________
StuM is offline   Reply With Quote
Old 16-01-2016, 23:12   #8
Registered User

Join Date: Oct 2011
Posts: 2,433
Re: Hp to displacement ratio

Thanks Stu. 80K sounds far more reasonable than 125K U.S. I suspect that they will do well with the boat. ____Grant.
__________________
gjordan is offline   Reply With Quote
Old 17-01-2016, 01:12   #9
Registered User

Join Date: Apr 2013
Posts: 4,877
Re: Hp to displacement ratio

Sounds pretty typical for that size boat.

Assuming the engine is in good shape and mated to an appropriate transmission and prop, should be fine.
__________________
valhalla360 is offline   Reply With Quote
Old 17-01-2016, 04:23   #10
Registered User

Join Date: Dec 2014
Posts: 97
Re: Hp to displacement ratio

Thanks everyone. Your comments are greatly appreciated.

Sent from my GT-I9506 using Cruisers Sailing Forum mobile app
__________________

__________________
nzmal is offline   Reply With Quote
Reply

Tags
displacement, men

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ballast/displacement ratio, and capsize screening ratio openseas Monohull Sailboats 6 28-05-2014 20:43
Displacement to Anchor Weight Ratio Sharki127 Anchoring & Mooring 56 26-12-2013 18:07
Your Power to Weight Ratio ( Sail area to displacement in kilos ) PooBeetle Multihull Sailboats 31 12-09-2012 05:17
Study for Sail Area / Displacement Ratio of some cats mamo Multihull Sailboats 155 16-05-2008 10:10



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 18:45.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.