Andrew_Fanner
Well-Known Member
Can never keep the wretched things working from one week to the next. I suspect there is a leak but Bennett's are not that able to help and tend to suggest a new pump.
Trim Tabs
- Thread starter GC1
- Start date
KevB
Well-Known Member
I have a friend who had leaky rams but was unable to get spares from the manufacturer. It wasn't that they didn't have any, they just didn't sell them. Ended up going to an diesel factors to get them reconditioned. /forums/images/graemlins/frown.gif
mjf
Well-Known Member
I agree with you. On my last boat when i had load of heavy peeps sitting / standing well aft the tabs made a huge difference to when I crossed the hump.
WOT - full trim tabs and away.
No trim tabs - and like a jumbo jet running down the runway getting airbourn eventually.......
WOT - full trim tabs and away.
No trim tabs - and like a jumbo jet running down the runway getting airbourn eventually.......
duncan
Well-Known Member
engines?
whisper
Well-Known Member
Mmm, unfortunately I did this this Summer following an attempt(successful) to get airborne /forums/images/graemlins/blush.gif
Powersalt
Well-Known Member
Funny on my boat they dont offer trim tabs as an extra. Said the hul didnet need them
GC1
N/A
Thank you for all the posts, I think I have the idea now, correct me if I am wrong, that when I look at the switches if I want say port bow down I press top left, if I want starboard bow down I press top right, if I want stern port down I press bottom left and if I want starboard stern down press bottom right /forums/images/graemlins/tongue.gif
Just one last question, when do I know when they are back to standby mode (where they started), there is no indicator so I would not know if I had them up down or whatever at any one time /forums/images/graemlins/confused.gif So if my thinking is right do I just press the bottom of both switches?
Just one last question, when do I know when they are back to standby mode (where they started), there is no indicator so I would not know if I had them up down or whatever at any one time /forums/images/graemlins/confused.gif So if my thinking is right do I just press the bottom of both switches?
hlb
RIP
You need the trim tabs up, for resting, so it grows no barnickles on the ram. Also safe as bow up is much safe're than down.
GC1
N/A
Thanks for the tip hlb, much appreciated /forums/images/graemlins/wink.gif
Callisto
Well-Known Member
Bit unusual Simon. On my Sprint I always used the leg for fore and aft trim and only corrected any listing to Port or Starboard with the tabs.
Usually, I put them right down to help her up when heaviliy laden (KevB is right on that point) as she reached planing, backed them right off then a simple tweak to get her level then trim the leg to get her flat. Callisto always had a starboard list due to the SP drive and the prop torque effect. your DP shouldn't do that.
Worked a treat for me anyway.
Jeff
Usually, I put them right down to help her up when heaviliy laden (KevB is right on that point) as she reached planing, backed them right off then a simple tweak to get her level then trim the leg to get her flat. Callisto always had a starboard list due to the SP drive and the prop torque effect. your DP shouldn't do that.
Worked a treat for me anyway.
Jeff
Callisto
Well-Known Member
If they are only manual tabs, use them carefully and adjust a little at a time if running at speed. It can be scary suddenly finding the boat with a very substantial list to one side cos you have over done it with the tabs. Been there, done it and got the brown trousers to prove it!
Best way i found to reset was to press the bottoms of both switches and hold for about 15 secs. Thats usually long enough for both to come back up to resting position.
Worked on mine anyway.
JH
Best way i found to reset was to press the bottoms of both switches and hold for about 15 secs. Thats usually long enough for both to come back up to resting position.
Worked on mine anyway.
JH
Its_Only_Money
Well-Known Member
[ QUOTE ]
Bit unusual Simon.
[/ QUOTE ]
Really???
From the Bennett site:
[ QUOTE ]
TRIM TABS AND POWER TRIM
It is a common misconception that if a boat has power trim on the outboard or outdrive it does not need trim tabs. Power trim can be used to adjust the boat's attitude, but it is highly inefficient. A propeller is designed to force the boat forward. When trimming the boat with the prop, the prop must not only push the boat forward but raise the stern as well. In this situation, prop slippage is greatly increased thereby wasting RPM's. Power trim cannot correct listing, and is ineffective at slower speeds. Bennett Trim Tabs, in combination with power trim, enable both the hull and prop to be trimmed independently. The trim tabs trim the hull, while the power trim adjusts the prop. The result is optimum performance and efficiency not attainable by the use of power trim alone.
To achieve maximum performance, first adjust the trim tabs to achieve the desired running attitude. Next, use the power trim to position the propeller thrust parallel to the water flow. If necessary, re-adjust the trim tabs to fine tune the attitude. By observing the boat’s speed and engine RPM's the best combination of trim tabs and power trim will be apparent. Trim tab angle indicators and a power trim angle indicator are particularly useful in duplicating effective settings.
[/ QUOTE ]
Works for me - certainly don't notice any decrease in performance or increaseed fuel when used in this way....
Bit unusual Simon.
[/ QUOTE ]
Really???
From the Bennett site:
[ QUOTE ]
TRIM TABS AND POWER TRIM
It is a common misconception that if a boat has power trim on the outboard or outdrive it does not need trim tabs. Power trim can be used to adjust the boat's attitude, but it is highly inefficient. A propeller is designed to force the boat forward. When trimming the boat with the prop, the prop must not only push the boat forward but raise the stern as well. In this situation, prop slippage is greatly increased thereby wasting RPM's. Power trim cannot correct listing, and is ineffective at slower speeds. Bennett Trim Tabs, in combination with power trim, enable both the hull and prop to be trimmed independently. The trim tabs trim the hull, while the power trim adjusts the prop. The result is optimum performance and efficiency not attainable by the use of power trim alone.
To achieve maximum performance, first adjust the trim tabs to achieve the desired running attitude. Next, use the power trim to position the propeller thrust parallel to the water flow. If necessary, re-adjust the trim tabs to fine tune the attitude. By observing the boat’s speed and engine RPM's the best combination of trim tabs and power trim will be apparent. Trim tab angle indicators and a power trim angle indicator are particularly useful in duplicating effective settings.
[/ QUOTE ]
Works for me - certainly don't notice any decrease in performance or increaseed fuel when used in this way....
Callisto
Well-Known Member
Each to his own I suppose. Mind you - Bennet are trying to sell tabs so they will naturally play up their usefulness.
I was always taught that tabs do give a bit of drag and hence I tried to use as little as possible.
The Bennet site is right that the prop needs to be as parallel to the water as possible but lets be honest, in any given sea condition, the angle of the prop relative to the surface of the water aint going to stay flat for long unless its like a mirror out there.
I guess different boats are affected in different ways. Your DP would not induce the list I had due to the SP drive so my tabs would have to be used in a different way/setting to yours to get the optimal speed and performance.
Would be interesting to see that attitude control system in action.
(Could think of a few on here who could do with an attitude control system too) /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
Are you keeing Ocean Deep in the oggin all winter or are you hauling out sometime soon?
Cheers
JH /forums/images/graemlins/cool.gif
I was always taught that tabs do give a bit of drag and hence I tried to use as little as possible.
The Bennet site is right that the prop needs to be as parallel to the water as possible but lets be honest, in any given sea condition, the angle of the prop relative to the surface of the water aint going to stay flat for long unless its like a mirror out there.
I guess different boats are affected in different ways. Your DP would not induce the list I had due to the SP drive so my tabs would have to be used in a different way/setting to yours to get the optimal speed and performance.
Would be interesting to see that attitude control system in action.
(Could think of a few on here who could do with an attitude control system too) /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
Are you keeing Ocean Deep in the oggin all winter or are you hauling out sometime soon?
Cheers
JH /forums/images/graemlins/cool.gif
Its_Only_Money
Well-Known Member
[ QUOTE ]
Are you keeing Ocean Deep in the oggin all winter or are you hauling out sometime soon?
Cheers
JH /forums/images/graemlins/cool.gif
[/ QUOTE ]
Dry-berthed on trailer so winter is no different - decent weather + opportunity and in she goes!
Hows the polishing going?
Are you keeing Ocean Deep in the oggin all winter or are you hauling out sometime soon?
Cheers
JH /forums/images/graemlins/cool.gif
[/ QUOTE ]
Dry-berthed on trailer so winter is no different - decent weather + opportunity and in she goes!
Hows the polishing going?
GC1
N/A
Thanks for the info /forums/images/graemlins/wink.gif
whisper
Well-Known Member
I'm not sure that that is unusual as it's the way we operate as well. Tabs are much better for controlling nose attitude than moving the leg in and out - on our boat anyway.
duncan
Well-Known Member
need to stay focused on cruise settings and quick fixes to condition changes - tend to be slightly differnt things, especially when one changes the other anyway - so to speak!
Seems to me the following are the cruising 'rules' for want of a better word - (and here I'm dealing with OD/OB propulsion)
1. You always want the propshaft parallel with the water as Kev said earlier. It's most efficient there and, if you don't have handed twins or duo props it is neutral steering too!
2.The hull will have a 'best angle' for any given speed/conditions etc - if you can't achieve this whilst maintaing (1) above then you will obviousl need to use the tabs, but don't forget to retrim as well.
3. Doing (2) above will normally result in increased drag and reduced economy for a well designed hull at it's normal running speed. Below this speed they can of course improve both. However having the slight additional tab and triming to (1) will normally be more efficient than less tab and the prop out of parallel................
(4) tabs should be right up at any speed in a following sea unless you are using them to sit just behind a crest and are maintaining wave speed. They are however inherently more dangerous than a trimmed in drive as you can reduced the effect of the latter but if a wave gets you accelerating down it's face the tabs will be working harder and harder to bury the nose.............. /forums/images/graemlins/crazy.gif
Seems to me the following are the cruising 'rules' for want of a better word - (and here I'm dealing with OD/OB propulsion)
1. You always want the propshaft parallel with the water as Kev said earlier. It's most efficient there and, if you don't have handed twins or duo props it is neutral steering too!
2.The hull will have a 'best angle' for any given speed/conditions etc - if you can't achieve this whilst maintaing (1) above then you will obviousl need to use the tabs, but don't forget to retrim as well.
3. Doing (2) above will normally result in increased drag and reduced economy for a well designed hull at it's normal running speed. Below this speed they can of course improve both. However having the slight additional tab and triming to (1) will normally be more efficient than less tab and the prop out of parallel................
(4) tabs should be right up at any speed in a following sea unless you are using them to sit just behind a crest and are maintaining wave speed. They are however inherently more dangerous than a trimmed in drive as you can reduced the effect of the latter but if a wave gets you accelerating down it's face the tabs will be working harder and harder to bury the nose.............. /forums/images/graemlins/crazy.gif
