making my cabin cruiser more efficient

[PT Man]

HI ALL
I Have a 2858 Bayliner Command Bridge with a new 7.5 L omc
outdriveI have been told by many people it is a pig I am looking for suggestions on redistibuting weight or anything that could be done to make it plane easier Any suggestion at all would be greatly appreciated.My back ground includes Mechanic & some engineering so I would like to hear from anyone with fresh ideas

[tom28571]

I suspect that you are going to have to face the fact of the basic design of your boat. The fundamental problem is not weight distribution but weight itself, or more properly, weight per square foot of bottom area. That is why they put big engines in these boats. Otherwise, they won't plane at all.

Transom trim tabs can help a boat get up on plane easier but they will not solve the basic problem of an inefficient hull. You can look at what might be done to eliminate some weight without ruining the structure or making the boat unsuitable as a cruiser.

[duluthboats]

They do have some things in the works.

http://www.boatdesign.net/gallery/sh....php?photo=117


Sorry, couldn't help myself. I'll have to defer to Tom on this one.

Gary

[Willallison]

I'll generally side on Tom's side with this one too, though I'll bet that if you look at a few of the possible reasons why your boat is performing so poorly, you could improve it somewhat.

To start with, how much extra weight are you carrying? No, no, no - not you - your boat! We all tend to pile on stuff over time - well now's the time to pull it all off again. Go through the whole boat. If you ain't used it recently, leave it at home.

Second, what state is your antifouling in? It only takes a little bit of growth on the bottom to slow you down .....No, no not you - I mean the boat again!! I once cleaned the bottom of a 23ft sportscruiser, powered by a 260hp sterndrive. Before, the boat could only just get on the plane and topped out at about 20knots - with a clean bottom she did 35....

Then you coluld check out your prop. Apart from making sure that its not full of dings, find out what pitch it is. I have a 27ft Searay which had a 19inch prop on it. I changed it to a 17 and whilst I have dropped a couple of mph in top speed, the boat is much quicker onto plane, will hold plane to slower speeds, is easier on fuel, and isn't stressing the motor as heavily.

Beyond that, I guess you could think about moving the motor fwd a bit and installing a short jack-shaft, but that's getting pretty serious and I suspect that you don't have the room in your engine room to do it anyway.

Of course, you do have a Bayliner, so you might just be better off buying a new boat!!!!
Sorry - couldn't help myself

[PT Man]

Hi All
I appreciate the quick responses antifouling is good prop has no dings. Tom28571 Do you really think the hull design is the problem or is it inside the hull. Willallison I never thought I would own a bayliner but I will tell you this is a pretty well built production boat. There is a lot of boat for little money. Anyway all suddestions welcome

[tom28571]

PT,

I don't have any specific knowlege of your boat, just general impression of similar Bayliner cruisers and other cousins of the same type. They tend to cater to first time buyer clients who want to carry all the comforts of home in a small boat and carry it fast. It's what the market wants and there is a price to pay. Some of that price is poor fuel efficiency and poor low speed performance.

Of course, as the others have said, there are some things that you may be able to do to improve the situation but I don't have any specific suggestions. Try contacting Bayliner and/or looking for a Bayliner web forum or addressing your question to other forums.

If the boat likes to stick its nose way up in the air before getting up on plane, then moving weight forward will probably help. If it just comes up normally but sluggishly, then you probably need (heaven forbid) more power or less weight. I doub't that Bayliner deliberately built a boat with a bottom that is detrimental to its performance.

And Will, whilst? I thought I was the old curmudgeon here. Haven't heard that for a month of Sundays.

[Polarity]

Owners website:
http://boc-web.org/ (1600 members!)
Discussion forum:
http://www.discussion-board.com/bayliner/

Hope that helps

[Willallison]

And Will, whilst? I thought I was the old curmudgeon here. Haven't heard that for a month of Sundays.


__________________
Tom Lathrop

I'm just a conservative traditionalist in radical go-fast clothing!

[Jeff]

Continued at http://forums.boatdesign.net/showthr...=&threadid=809

[FRANKIEFRANKIE]

Originally posted by PT Man
Hi All
I appreciate the quick responses antifouling is good prop has no dings. Tom28571 Do you really think the hull design is the problem or is it inside the hull. Willallison I never thought I would own a bayliner but I will tell you this is a pretty well built production boat. There is a lot of boat for little money. Anyway all suddestions welcome

INSTEAD OF TRIM TABS YOU CAN SIMPLY LENGTHEN YOUR BOAT VIA AFTERPLANES. AFTERPLANES ARE SIMILAR TO TABS EXCEPT THEY ARE PERMANENT AND FOLLOW THE DEADRISE OF YOUR BOAT. YOU COULD MAKE THEM COME OUT ABOUT 12 TO 18 INCHES AND MAKE THEM OF FIBERGLASS LIKE YOUR BOAT. DO NOT MOVE THE ENGINE FORWARD. THE OTHER THING I WOULD SUGGEST IS TO LOOK AT THE BOTTOM OF YOUR BOAT AND TAKE A STRAIGHT EDGE (A LONG 4FOOT OR SO PIECE OF METAL BAR) AND CHECK TO SEE HOW STRAIGHT YOUR BOTTOM IS OR IF THERE IS A TWIST IN IT. IF YOU ADD THE AFTERPLANES THEY NEED TO BE STRAIGHT LIKE IF YOU CAN GET A CIGARETTE PAPER BETWEEN THE BOAT AND THE STRAIGHT EDGE.

HAVE A FEW MORE SUGGESTION INCLUDING A TRIMMABLE SURFACE DRIVE.

[PT Man]

HI
These after planes any literature about them or affects. This sounds pretty encouraging. As far as the bottom being straight can any one elaborate on cause & effects
Thanks
Mike

[FRANKIEFRANKIE]

Originally posted by PT Man
HI
These after planes any literature about them or affects. This sounds pretty encouraging. As far as the bottom being straight can any one elaborate on cause & effects
Thanks
Mike

The affects of afterplanes (which you see on raceboats alot and all military ships) is that it makes your boat longer, in your case to change the weight per square foot. Bigger boat less weight. The Navy gave their engineering depart an award last year check their web site, for putting afterplanes on all their big ships which gave them a tremedous savings in fuel. Of course we have been doing this for 30 years are better. Just don't have the right connections.

On the being straight part, just for fun sit in the bath tub and take a crooked stick and an straight stick and see which one moves faster through the water. You don't want a twist in you hull and you really don't have to be as straight as a cigarette paper but the closer the better.

Hope this helps.

Frankie

[tom28571]

PT,

Imagine that you take a knife and slice the boat down the middle from stem to stern along the keel so that you have two symmetrical half hulls. Now make other parallel slices in the same plane at equal intervals out to the chine. The intersection of these slices with the hull are called buttocks lines. In the after part of the hull bottom these lines must be as straight as possible to avoid unnecessary drag. I prefer that the aft buttocks also be parallel as well as straight. This shape of hull is called a monohedron. Some designers prefer that the aft buttock lines be straight but not completely parallel so that there is a twist in the bottom surface. This is called a warped plane bottom and is supposed to make initial planing easier.

In any event, if there is any convex curvature (rocker) in any of these lines in the area of the aft planing surface, wave making drag will be increased and planing will be harder to achieve. That is what Frankie is talking about. Unless there is some kind of screwup, I doubt that Bayliner made such a mistake.

[PT Man]

Hi
Is there any way this could happen to a boat later in the boats life.
Thanks

[FRANKIEFRANKIE]

Yes, there are a lot of ways this could happen at the factory or after the factory. Remember that a Bay Liner is a Bay boat not an ocean going boat. It is made better than a Sea Ray but with less advertising.

Good luck and don't forget about the trimmable surface drive for lower planning speeds and lower rpm speeds = fuel economy.