Trim Tabs

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David of Essex

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This is my SD boat which has no trim tabs fitted. If trim tabs were fitted would they level the boat up from the angle shown and would performance be decreased, or increased. Also is there any +or-from fuel consumption.
 
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David of Essex said:
This is my SD boat which has no trim tabs fitted. If trim tabs were fitted would they level the boat up from the angle shown and would performance be decreased, or increased. Also is there any +or-from fuel consumption.
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The picture shows your boat to be running fairly nicely
As hlb says-- 'bow down' can be usefull for running into heads seas.
So thats one handy element of tabs
Raising and lowering the bow depending on conditions
Dunno how your boat behaves ref 'tilt'

Using tabs to level the vessel 'athwatrs' can be usefull too
What's the boat
Looks a bit Rodman ish
Without clikin on the piccie again!

Fitted some 'QL' tabs (leccy not hydraulic ones) to 3 boats now
25 to 30 footers
They seem to work well too
 
Have you tried better weight distribution - i.e., storing beer/wine/heavy stuff in the v-berth?

Although (as has been said) I too thought SD craft tended to ride a little bow-high generally?
 
I would say she looks good, I have a Rodman 900 which would be similar if a little heavier than your boat, first pic is a friends 900 without tabs and 2nd photo is my boat with tabs about half way down.

I get maybe a knot more when trimmed correctly but differs hugely with sea state.
 
carlton said:
Although (as has been said) I too thought SD craft tended to ride a little bow-high generally?
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Yes, quite correct generally
Like any boats
There are semi displacement vessels and semi displacement vessels!

Without going into all the makes and sizes etc

I can only refer to my experiences of helming such craft over the last 30 years

Some ride really high at their optimum speed
Others can be really quite flat.
It depends on hull form and length obviously.

I aint no hull expert
It's just what I have experienced:)
 
The boat is a Merry Fisher 925. When running at SD I'am a bit concerned about the angle seems a bit steep and a slight safety concern when moving from the saloon to the rear seating area outside. ( don't want a MOB situation )
That's a good idea about weight distribution. More anchor chain in the bow.
David
 
David of Essex said:
The boat is a Merry Fisher 925. When running at SD I'am a bit concerned about the angle seems a bit steep and a slight safety concern when moving from the saloon to the rear seating area outside. ( don't want a MOB situation )
That's a good idea about weight distribution. More anchor chain in the bow.
David
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I put a load of extra anchor chain on last year. Runs with the bow quite a bit lower now.
 
Actually, bow high is the safest mode, if there is no option. Bows low in a following sea can be fatal. You can add more chain, but you will pay for it in speed and fuel.

Fitting trim tabs may be a good idea. Or you may find you never use them.
 
Your boat would benefit extremely with a set of 'QL' electronic trim tabs.
Yes
Weight distribution too
As per anchor chain in the bow etc
I bet you are like any other boat owner
We 'hump' more and more bits an bobs onto our boats weekly!!

'That's a handy gadget, I need one of those
Need some more food/booze and one of them an that looks handy plus an extra bit of fuel that tank will do, oh yeh an a gizmo plus an extra anchor an a bit more rope an chain an a telly an micro summat or other an some solar panels to run the gizmo an another boat hook an a few fishin rods and some Fray Bentos tins an beans and spuds an a liferaft an a dinghy ana seagull frightener and and and and!!!

Trim tabs will help
 
That boat may suffer from leaning into the wind as well? Trim tabs would help the boat to run better - I would add to the comments about adding weight to the bow of any boat - it turns into a big handicap if not danger when running downwind.
 
Cookee said:
That boat may suffer from leaning into the wind as well? Trim tabs would help the boat to run better - I would add to the comments about adding weight to the bow of any boat - it turns into a big handicap if not danger when running downwind.
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Good post Cookee
Manufacturers of boats (plus cars etc etc) spend quite a bit of time and making stuff that works ok

Then as boaters
We 'alter' things
Stick more kit on and fuel tanks etc etc etc
Then the vessel behaves quite differently
Add ons mods 'tuning'!
I have seen this type of thing in the car, motorcycle and boat world over the years.

Weight distribution is so important with boats to get them to 'ride' properly.

As you quite rightly say
To compensate for a boats 'attitude' by lobbing weight forward
Or in the stern ,come to that
Is not a permanent 'fix'


Semi displacement
We hear a lot about that

Good hull type for most sea conditions
Compromise however
Fully planing hulls
OK when the water is flat
Displacement hulls
No need to 'trim' as it where
But, yes, occasionall depending on size
Weight distribution with a displacement hull?
Yep More weight in the keel helps with some

Planing hulls?
Deffo need to adhere to weight distribution

Especially before reaching 'on the plane', again depending on which hull design.

'Semis that Plane'?
No such thing I hear you say
Yep
The likes of the 925 will get into planing mode-- ish
Therefore trimtabs are a good idea
Not a bag of coal or tons of anchor chain
Yep
This may work most of the time
But it aint the way forward
See
'Forward' get me drift:D:rolleyes::rolleyes:
 
David of Essex said:
This is my SD boat which has no trim tabs fitted. If trim tabs were fitted would they level the boat up from the angle shown and would performance be decreased, or increased. Also is there any +or-from fuel consumption.
Click to expand...


Running angle looks fine to me (even when you allow for the fact the horizon isn't straight in that photo). I wouldn't bother fitting tabs to change that running angle

Also the boat very much looks like it's planing, not semi-D-ing, in that pic
 
Thanks for all your comments about trim tabs it is a leaning curve. It seems that it not a most have situation, more of could be an improvement.
ps thats my son Scott at the helm, I'am older.
David
 
Sorry to piggy back this one

I am thinking about adding trim tabs to a similar boat. Picture shows her at 10 knots. Flattens a little at fast cruise pace. Are they effective on this type of boat ie semi-displacement? Would love to know of others who have seen an improvement....
 
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thejonesey said:
Are they effective on this type of boat ie semi-displacement?
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Just a very little I guess - if anything at all.
10kts is an awful speed for any small planing hull (which is what she looks like, rather than SD).
You'd better choose to either get along at 6kts or go faster.
 
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