Trim Tabs

larglo · Post by **larglo** » Mon Feb 28, 2011 2:08 pm

Hi all,

In a previous post concerning trim tabs and planing, is it permissible to set the trim tabs at the location that seem to allow the boat to trim best at,,,,,and leave them there? Not having to adjust them on each outing.

Larry

captainmaniac · Post by **captainmaniac** » Mon Feb 28, 2011 2:22 pm

'Permissible', but not optimal. The whole idea of the tabs is to help the boat run at an optimal angle (bow up/down, as well as levelling it side to side). You use them like the flaps on airplane. You are not really adjusting them on each outing - you should be adjusting them as needed the entire time you are out on the water.

If you set them for optimal running angle at normal cruise speed on a given day and leave them there, they will work well for that speed on future runs as long as you have the same loading conditions (relative weight fore and aft, and side to side) and wave conditions.

But, move more weight forward, now you are bow down and possibly pounding or having a wetter ride. Move weight back, you will be bow high and possibly porpoising. One extra 200 pound passenger sitting on one side and you have a list affecting steering. Plus they won't be doing you any favours at different speeds and in wave conditions, and could even prove dangerous in following seas (when you really want the tabs up higher than normal).

Now, having said all that, if you go back a few decades there was a time when trim tabs were not hydraulic - they were essentially fixed although you could adjust the angle by taking a wrench to them. So .. permissible, yes... but you and your passengers will have a much more enjoyable, efficient, and safer ride if you adjust them as required while underway.

jimbo36 · Post by **jimbo36** » Mon Feb 28, 2011 2:37 pm

Well put CaptainM, Couldn't have said it better myself.

jimbo36

captainmaniac · Post by **captainmaniac** » Mon Feb 28, 2011 2:41 pm

I aim to please

randyp · Post by **randyp** » Mon Feb 28, 2011 4:22 pm

I find that when I have too many passengers loading the boat and messing up my trim I just chuck them overboard. But seriously, folks......I set the trim tabs underway and usually at or around "planing" speed on the F-26, which seems to be over 2500 rpm. I check the GPS speed to see wassup after that so I can finetune things with the tabs. Capt M is correct that the loading, conditions, etc are too variable to just set em and forget em. I don't use the tabs when I'm running under 1600-1800 rpm (again, single Chrysler 318/225 hp). The F25 and F26 aren't really planing hulls so the tabs are great once you get the old girl up and a bit out of the water. I try to find the "pocket" each time I'm running at or around optimal high end speed, which seems to be 3000-3200 rpm (or about 80% WOT). It's never the same so it makes sense to tweak the tabs each time. When I'm out with the kids and their kids (and those little critters like to roam all over.....and I can't really chuck them overboard until they learn how to swim better....)I find I'm tweaking the tabs a lot. But it only takes a quick flick on the controls to get things back to "the pocket".

captainmaniac · Post by **captainmaniac** » Mon Feb 28, 2011 4:45 pm

Actually, that is a key point Randy just mentioned... Changing the tab position will not have an instantaneous affect on the boat - it will take a couple of seconds for the boat to react and for you to understand if you still need more or have gone too far.

When fine tuning trim, do it with small adjustments only. Give the control a tap or two then wait a few seconds for the boat to respond. Then tap a bit more or 'undo' a tap if you over trimmed. If conditions stay the same and your crew sits on their butts for a while, no further adjustments should be needed until something changes.

prowlersfish · Post by **prowlersfish** » Mon Feb 28, 2011 6:37 pm

What works at 16 knots Don't at 20 , what works with full load will not when lite .

foofer b · Post by **foofer b** » Mon Feb 28, 2011 7:38 pm

While not really a concern where you are, when the seas get a bit rough, you have a whole new set of variables with which to contend. Following seas, quartering seas, and bow on, all require a little experimenting. The F25/26's do not have "blue water" hulls and can be a chore to navigate, regardless of trim!!

Oh and I don't throw anyone overboard, I just tie them to their chair if they mess with my track/trim by walking around!

wowzer52 · Post by **wowzer52** » Mon Feb 28, 2011 9:40 pm

After "keel hauling" they seem to settle down also.

captainmaniac · Post by **captainmaniac** » Mon Feb 28, 2011 9:44 pm

Another way of making sure passengers don't move around and screw up your trim ... don't take any (unless they pay for the fuel)!!

randyp · Post by **randyp** » Mon Feb 28, 2011 9:55 pm

And that's the WINNER! Especially with the way fuel's gonna go this year. Or maybe, better yet, tie em down and make em row....

captainmaniac · Post by **captainmaniac** » Mon Feb 28, 2011 10:00 pm

randyp wrote:And that's the WINNER! Especially with the way fuel's gonna go this year. Or maybe, better yet, tie em down and make em row....

Nah... you'll never get on plane that way. It's no fun unless you get on plane!

randyp · Post by **randyp** » Mon Feb 28, 2011 10:09 pm

Not even if you beat the drum faster and use the whip?

captainmaniac · Post by **captainmaniac** » Mon Feb 28, 2011 10:56 pm

Didn't work for me. Had 17 aboard when we hosted my sister's wedding out on the harbour a couple of years back and couldn't get over 6 knots. Actually, I was too scared to!!!

Carrying 3000+ extra pounds of human blubber affects boat behavior 'just a tad', and when I saw the pictures later I discovered I was sitting about 6" lower in the water than normal, with a list depending on where everyone was sitting or standing at the time! I should have see it coming - normally when people come aboard the boat will dip as they step on, then rock back to where it was... As this gaggle of relatives came aboard I noticed it just kept going down, and down, and down, and down..

Anyways, carrying that much extra weight, she don't stop on reverse or turn quite the same as normal... Almost made for a very embarrassing docking attempt at the Club in front of 100 more Reception guests (but fortunately, I am gooood at the controls...). Always helps the ego when you get applause from that many people (okay... maybe it was for the bride and groom, but they wouldn't have been there it if it wasn't for me

).

Lesson learned : How many people is it safe to take out on an F32? Answer : I don't know, but its less than 17!!!

foofer b · Post by **foofer b** » Tue Mar 01, 2011 6:54 am

know what you mean Maniac about the extra weight. When I take four of us beefy divers out with our 200 lbs of gear each (at least) or more for three tank dives, she will only plane out if the spare tanks are on the front cabin sole and the spare beef goes to the bow!!! And she doesn't want to even then!!