Cruisers Forum
 


Join CruisersForum Today

Closed Thread
 
Thread Tools Rate Thread Display Modes
Old 25-12-2010, 10:51   #31
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,586
Images: 240
Quote:
Originally Posted by beau View Post
Sorry you are wrong. My boat has a theoritical hull speed of 8 knots yet is does 15 knots. and it is not planeing.
It does not sit on top of the water but slices through the water.
To plane you need the right hull shape and 60 hp/per ton, my power to weight ratio is 25hp/ton

Why, because it has a very fine angle of entry, triangular hull shape and a flat bottom.
No bow wave is produced and the stern wave flattens out after 10 knots.
Don't believe it, just look at all the fast displacement catamaran and trimaran ferries and the latest USA naval vessels sourced from Australia ...
What you describe is not a conventional displacement hull, and the conventional formula for theoretical hull speed will not apply.
__________________

__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline  
Old 25-12-2010, 11:27   #32
Registered User

Join Date: Mar 2010
Location: southcoast ontario ca
Boat: Georgian 23 Whiskeyjack
Posts: 296
Images: 1
Quote:
Originally Posted by beau View Post
Sorry you are wrong. My boat has a theoritical hull speed of 8 knots yet is does 15 knots. and it is not planeing.
It does not sit on top of the water but slices through the water.
To plane you need the right hull shape and 60 hp/per ton, my power to weight ratio is 25hp/ton

Why, because it has a very fine angle of entry,triangular hull shape and a flat bottom.
No bow wave is produced and the stern wave flattens out after 10 knots.
Don't believe it, just look at all the fast displacement catamaran and trimaran ferries and the latest USA naval vessels sourced from Australia.

Chief engineer, what are you trying to say?

Bljones, well why are Tohatsu suggesting a prop repitching to stay in warranty. ( but at my cost)

Sorry, I wasn't going to reply to all those negative uninformed responses but i could not resist. i suppose that is the internet for better or for worse.
Ah, you have a SEMI-displacement hull. Got it. You repeatedly described your boat inaccurately as a displacement hull. Uninformed posts tend to get uninformed answers. Merry Christmas.
__________________

__________________
bljones is offline  
Old 25-12-2010, 12:08   #33
cruiser

Join Date: Aug 2006
Posts: 205
Wow some hard comments here.

Quote:
Originally Posted by beau View Post
Recently I purchased 2 X 90 hp Tohatsu outboards in Brisbane, Australia.
The motors are fine, but the service from the Local dealer and the Australian distributors has been far less than ideal.

Quote:
My boat is a Non planeing (fast displacement) which was fully explained before purchase, (they visited the boat).
With the Standard prop's I could only get a max 3,000 rpm, I asked for a finer pitch prop 14X11 which they supplied, which gives me 4,500rpm.
However the motors should have a max rpm of 5000-5,5000.

Apparently, Tohatsu only have two size prop's available in this range, both sourced from Mercury and both are only suitable for planning boats

The Tohatsu dealer and the Australian distributor have therefore refused to supply me with the required prop's 14 X 9 (available from Mercury) and they have also told me that if i use the current props 14X11 I will veto my warranty.??

Two new props will cost me an extra $600.00

Is there anything I can do.
I have no reason to disbelieve what you write and in view of this

Quote:
My boat is a Non planeing (fast displacement) which was fully explained before purchase, (they visited the boat).
It seems to me they want to blame you for their incompetence.

If you call me to come to your home and install an A/C unit and it doesn't cool your home who's fault is that? Are you the A/C professional?

IMO they owe you a refund or the correct wheels.

Now if you have been less than accurate here that's another story but based on your post I'm on your side.

__________________
Noname1 is offline  
Old 25-12-2010, 15:09   #34
Registered User
 
beau's Avatar

Join Date: Dec 2006
Location: Brisbane Australia
Posts: 757
Images: 1
Quote:
Ah, you have a SEMI-displacement hull. Got it. You repeatedly described your boat inaccurately as a displacement hull. Uninformed posts tend to get uninformed answers. Merry Christmas.
No the design is NOT semi displacement, at no point are the hydrodynamics of planeing at work.
Basically the bow entry is so fine below the waterline that No bow wave is formed, the hull does not have to lift to get over or on top of the bow wave because there isn't any.
Attached Thumbnails
Click image for larger version

Name:	basic drawing.jpg
Views:	72
Size:	261.2 KB
ID:	22234  
__________________
beau is offline  
Old 26-12-2010, 08:46   #35
Registered User

Join Date: Oct 2009
Posts: 648
Quote:
Originally Posted by never monday View Post
The engineers at Tohatsu / Nissan Marine have established parameters the engine should be run in to achieve minimum emissions, maximum longevity and minimum warranty claims.
There are known formulas to calculate performance from a current result. The dealer has determined that you need less pitch on your prop.
The dealer AND the manufacturer do not offer the prop pitch you require.
The question that I would have is how is warranty service void(or is it) if the engine is put on a "too large" a boat so that max rpm can not be achieved? Apparently the warranty is void if you put a finer pitch prop on the shaft so then it would appear there is no solution other than getting a smaller boat. That should have been established up front however maybe the warranty is still valid even if you can not achieve the max rated rpm.??
__________________
lancelot9898 is offline  
Old 26-12-2010, 08:59   #36
Registered User

Join Date: Jun 2005
Posts: 1,901
Quote:
Originally Posted by lancelot9898 View Post
The question that I would have is how is warranty service void(or is it) if the engine is put on a "too large" a boat so that max rpm can not be achieved? Apparently the warranty is void if you put a finer pitch prop on the shaft so then it would appear there is no solution other than getting a smaller boat. That should have been established up front however maybe the warranty is still valid even if you can not achieve the max rated rpm.??
the warranty issue is from over loading the engine with too much pitch. This doesn't allow it to get to it's designed RPM range.
Yes, he's installing a finer prop than the engine was delivered with. But it's not fine enough. Tohatsu doesn't offer anything finer to raise the RPM to design spec. I don't know why.

This leads me to believe the engine is too small to meet the needs of the boat. Or, conversely the boat is too large for the engine.
__________________
never monday is offline  
Old 26-12-2010, 09:29   #37
Registered User

Join Date: Oct 2009
Posts: 648
Quote:
Originally Posted by never monday View Post
the warranty issue is from over loading the engine with too much pitch. This doesn't allow it to get to it's designed RPM range.
.

Does that void the warranty?
__________________
lancelot9898 is offline  
Old 26-12-2010, 09:38   #38
Registered User

Join Date: Jun 2005
Posts: 1,901
Quote:
Originally Posted by lancelot9898 View Post
Does that void the warranty?
It can at manuf discretion. Every warranty I've dealt with has required certification of maximum RPM underway.
__________________
never monday is offline  
Old 26-12-2010, 09:54   #39
Registered User

Join Date: Oct 2009
Posts: 648
Quote:
Originally Posted by never monday View Post
It can at manuf discretion. Every warranty I've dealt with has required certification of maximum RPM underway.
Thanks. When I took delivery of my new boat back in '85 there was no certification of max rpm while underway. That was for a Perkins 4-108. I've also bought several small outboards new over the years and I was never asked what they were to be mounted on much less going for a ride to certify the rpm. Maybe after a problem arises and warranty service is required then measurements will be made after the fact to justify not covering warranty service. Just saying.
__________________
lancelot9898 is offline  
Old 26-12-2010, 10:21   #40
cruiser

Join Date: Aug 2006
Posts: 205
Dealer can plug into the engine computer on newer engines and read the log. If you have been abusing the engine it will be in the log.
__________________
Noname1 is offline  
Old 26-12-2010, 11:20   #41
Registered User

Join Date: Jun 2005
Posts: 1,901
Quote:
Originally Posted by lancelot9898 View Post
Thanks. When I took delivery of my new boat back in '85 there was no certification of max rpm while underway. That was for a Perkins 4-108. I've also bought several small outboards new over the years and I was never asked what they were to be mounted on much less going for a ride to certify the rpm. Maybe after a problem arises and warranty service is required then measurements will be made after the fact to justify not covering warranty service. Just saying.
A) times have changed since 1985

B) I have forms from every manuf i represent requiring this. The larger the engine the more detail that is required. Volvo being the most stringent in application performance certification.
__________________
never monday is offline  
Old 26-12-2010, 15:14   #42
Eternal Member
 
Chief Engineer's Avatar

Join Date: Aug 2006
Location: North of Baltimore
Boat: Ericson 27 & 18' Herrmann Catboat
Posts: 3,798
To the original poster:

There is a whole lot of "he said-she said" going on.

There are a number of us, mechanics and knowledgeable yachtsmen,
who can guide you in the right direction.

We do not get paid for this. (although I have gotten several jobs from this board) {one of whom ended up as being a deadbeat}

What we need to know is:

Who built the boat
What are the design parameters

I viewed the photo of the vessel.....I am supposing it is a trimaran of some kind?
__________________
Chief Engineer is offline  
Old 26-12-2010, 15:30   #43
Senior Cruiser
 
Blue Stocking's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: St. Georges, Bda
Boat: Rhodes Reliant 41ft
Posts: 4,117
Chief,

Isn't this the same boat about which the OP had considerable discussion a few week back, relating to design and performance.
If I remember correctly, he went into great detail about design and performance, which make me wonder why this thread has become such a
Jus' curious.
__________________
so many projects--so little time !!
Blue Stocking is offline  
Old 26-12-2010, 15:33   #44
Registered User
 
beau's Avatar

Join Date: Dec 2006
Location: Brisbane Australia
Posts: 757
Images: 1
Some of you guys just don't get it.
The tohatsu dealer suggested the repitching of the props, to 14X9 the problem was I did not think I should pay for it, when they had suitable props available from mercury.
Attached is the latest US navy ship built by Austal (Australian Design) in Mobile Alabama.
Fast, displacement.
Attached Thumbnails
Click image for larger version

Name:	usa navy.jpg
Views:	73
Size:	166.5 KB
ID:	22266  
__________________
beau is offline  
Old 26-12-2010, 15:44   #45
Eternal Member
 
Chief Engineer's Avatar

Join Date: Aug 2006
Location: North of Baltimore
Boat: Ericson 27 & 18' Herrmann Catboat
Posts: 3,798
I don't know...........maybe

How about posting a link to that original thread?

There are a lot of knowlegedable people on this board.

I hesitate to use the word mechanic...........because

there is more to it than just turning a wrench.........

After having a number of initals after my name.........



I prefer to work on boats


Ingo Swann?
__________________

__________________
Chief Engineer is offline  
Closed Thread

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
Bad Experience in Sidney, BC joebigsky Pacific & South China Sea 19 16-11-2015 11:02
Teak Dealers in Vancouver or Online ? rdempsey Construction, Maintenance & Refit 5 07-04-2010 09:52



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 21:58.


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.