inclinometer - correct way to measure running angle?

[BobCT]

What's the correct way to measure the running angle? I saw Bob's post that the Internationals run around 5.5%, essentially uphill. Should the gauge be set to zero as a starting point? At rest, my boat is pretty close to level, looks to be around 1- 1.5 degrees. I got this measurement by holding the gauge next to the side window at the helm. That appears (just by eye) to be parallel to the deck. In hindsight, I guess I could have compared the two.

On that basis, I went for a run and it seems to be between 5-6 degrees but it feels a little more "uphill" with the new engines but that's just by memory. The gauge I have isn't dampened so it's a little tough to read, it was perfect for measuring the shaft angle. I know that I have some weight shift towards the rear because the transmissions are about 3.5" shorter than the old ones. I bought 200lbs of shot weight in bags which I was planning to throw under the v-berth. I'm still running tabs all the way down just like with the 454's.

I would like to add enough weight in the bow so that it actually runs too low and allow me to back the tabs off (up) a bit. I'm never run them anywhere but all the way down since I bought the boat. I know there's diminishing returns if I add too much because I'm carrying around more weight. 200lbs seems like a good start but that's just a guess.

RWS, you went through this before didn't you?

Bob

[El L Sea]

To us, running angle depends on seas. Definitely bow high, but we trim for speed. That said, based on how much weight we usually have, I have never touched a trim tab in years.

[RWS]

Hi Bob,

I'm inserting responses into your text for clarity.

What's the correct way to measure the running angle? I saw Bob's post that the Internationals run around 5.5%, essentially uphill. Should the gauge be set to zero as a starting point? At rest, my boat is pretty close to level, looks to be around 1- 1.5 degrees. I got this measurement by holding the gauge next to the side window at the helm. That appears (just by eye) to be parallel to the deck. In hindsight, I guess I could have compared the two.

I believe we are seeking to measure the DIFFERENCE between at rest and on plane.

I bought a sailboat inclinanometer like this:

https://www.amazon.com/Sun-Company-Lev- ... s9dHJ1ZQ==

I filled up the water & fuel tanks and set it at ZERO at the dock.



On that basis, I went for a run and it seems to be between 5-6 degrees but it feels a little more "uphill" with the new engines but that's just by memory. The gauge I have isn't dampened so it's a little tough to read, it was perfect for measuring the shaft angle. I know that I have some weight shift towards the rear because the transmissions are about 3.5" shorter than the old ones. I bought 200lbs of shot weight in bags which I was planning to throw under the v-berth. I'm still running tabs all the way down just like with the 454's.

I would like to add enough weight in the bow so that it actually runs too low and allow me to back the tabs off (up) a bit. I'm never run them anywhere but all the way down since I bought the boat. I know there's diminishing returns if I add too much because I'm carrying around more weight. 200lbs seems like a good start but that's just a guess.

RWS, you went through this before didn't you?

I'm no naval architect or engineer, but it seems logical to me that the goal here is to improve the running angle of the vessel for performance and economy. Prior to the repower, with any serious weight or passenger load on board she felt ass heavy..... VERY ASS HEAVY! I wanted to get her ass end up. Thats the reason for all the time spent with TABMAN (R.I.P) at Bennett Marine on the longer tabs with the drop fins. This resulted in big gains in performance and economy. I would suggest that putting additional weight on the boat will not accomplish your goal of improving the running angle. I don't see how the extra weight would get the ass end up. Lots of discussion on the Forum on that longer tab w/drop fin modification.

Please keep us in the loop as you fine tune this repower. We're all excited for you !

RWS

Bob

[BobCT]

Unfortunately, I think I'm out of tab options as I already upgraded to 12x24's and added drop fins a while back. My theory, doing some rough math, I shifted about 200lbs towards the stern because of the engines moving aft about 3.5". Being able to stand in front of the engines for maintenance is priceless so I don't regret this decision. Plus it saved me the cost of new shafts.

I was thinking more along the lines of getting the bow DOWN to achieve the right angle vs bringing the stern UP (and between 4 blade props and my tabs, I think I'm out of options here regardless). Does bringing the bow DOWN move the aft UP or does it simply move the bow downward? And the million dollar question, does that matter if you ultimately achieve the correct angle?

You answered my burning question, it's the difference between @ rest and on plane. I ordered the same inclinometer since I can mount it (at zero) and play around with the numbers. I really wish I did this on my last run before pulling the old engines so I had some hard data.

Ok, I'll play around with this some more.

thanks

[RWS]

"I was thinking more along the lines of getting the bow DOWN to achieve the right angle vs bringing the stern UP (and between 4 blade props and my tabs, I think I'm out of options here regardless). Does bringing the bow DOWN move the aft UP or does it simply move the bow downward? "


IMHO there is a difference between pushing against a hard, unyielding surface vs. pushing against water.

I believe the desired result will come from LIFT.

Interesting side note:

With the 454 Crusaders I was running a flowscan and an ENSIGN digital tach/sync.

slight adjustments to the tabs yielded big results in fuel economy, and were always different based on load, speed, sea conditions and wind.

Tony Athens preaches that it's the props that move the boat, not the engines.

The Yanmars are 315 horse, the Crusaders were 330/350 horse, albeit a bit tired, one had over 2400 hours

the big surprise with the diesels was that while the tabs would change the running angle, the tabs truly made no difference in speed or fuel burn.

I would suppose the reason for this is the bigger props with more torque behind them creating more lift - but that's only my guess

I believe the lift is precisely what changed the running angle of this boat

You now have more torque and HP than before your repower, the only other difference is shifting some weight aft. Given the length and beam, how could that be so significant? 100 gallons of fuel is 840 lbs !

Do you have the drop fins on your tabs?

RWS

[prowlersfish]

Bob, Are you trying to get it level or are you trying to get the most efficient angle?

[prowlersfish]

Bob, Are you trying to get it level or are you trying to get the most efficient angle?

[BobCT]

RWS, yes I do have drop fins. I agree, in the grand scheme of things, the weight shift is pretty minor. I mean, I could keep my holding tank closer to full if I really wanted to (4O gallons under the v berth). The reason I opened this up was because of the trim tabs. I was hoping with the new engines that I could run them anywhere but fully down. That's definitely not the case so far and if anything, it feels a little more bow high. Not drastically but certainly not lower.

Prowlerfish - Bob posted that 5.5 degrees is the sweet spot on the Internationals so that's the goal. I know that's not level but that's where this hull wants to be for maximum efficiency.

Once I get this new inclinometer, I'll get a better measurement underway.


Bob

[prowlersfish]

Bob, Just making sure you're not trying to get it level. I have a meter mounted on the flybridge. It kills me having a sailboat part on the boat .

[BobCT]

Yep, I'll feel the same way! Prob mounting mine tonight.

[Goran]

It kills me having a sailboat part on the boat .

HaHaHa , good one

[Boppy]

I’m an old rag boater but never used an inclinometer on the F26. I use rpms and speed and tweak the trim tabs for best performance, ie speed on the gps vs rpms on the tach. With no tabs (I lost hydraulic fluid crossing Lake Oneida years ago) the boat was definitely ass heavy. For me it’s the way I find the sweet spot running at cruising speed, which is 80% of WOT or 3000 rpm on a single Chrysler 318

[captainmaniac]

Have posted on this subject a couple times before, but I don't think you really need an inclinometer...

Bring the boat up to a certain RPM (that is good planing speed), you can play with the tabs to find the best running angle. Don't mash the tabs, just tap them a half second or so at a time. Up or down, just adjust the tabs a hair at a time and see what it does for RPMs and speed. The boat's response will not be immediate - do a tweak and wait 5-10 seconds, and see what happens, then tweak up or down a bit more. It takes time for the boat to respond. Best running angle is whatever ends up giving you best speed for a given RPM. You may find you can hit an RPM, trim for best speed, then throttle back for the speed you want!.

Once you have done this a few times, you will get a sense of how much tab you need to use and how to most effectively apply it. From my experience, and example could be: running at idle, tab full down, push to 2000RPM, once settled push to 2500RPM and give 3 seconds of tab up.. then throttle to 2800 with 1 second tab up.... then tweak tab up or down based on whatever works best for current wind / wave conditions.

Also, hard to describe the feeling, but you will actually FEEL the boat is running more free, and not fighting things when you have it dialed in. If you are dialed in to what is going on around / under you, you can actually feel the difference between smooth running (floating on a cloud) ride vs the boat fighting it.

Desired running angle is a factory / design concept. What is right for you depends on how the boat is loaded, where the weight is, if there is any water absorption in the hull, etc., and the older the boat is the more likely previous owners or you have evolved the boat from factory specs. The best running angle for you depends on your what has happened with your boat over the years, not factory specs.

B Side:
If someone has done some really bad things like adding hundreds of pound forward, or aft, that throw the whole balance off, you may not be able to adequately compensate.

[RWS]

Have posted on this subject a couple times before, but I don't think you really need an inclinometer...

Bring the boat up to a certain RPM (that is good planing speed), you can play with the tabs to find the best running angle. Don't mash the tabs, just tap them a half second or so at a time. Up or down, just adjust the tabs a hair at a time and see what it does for RPMs and speed. The boat's response will not be immediate - do a tweak and wait 5-10 seconds, and see what happens, then tweak up or down a bit more. It takes time for the boat to respond. Best running angle is whatever ends up giving you best speed for a given RPM. You may find you can hit an RPM, trim for best speed, then throttle back for the speed you want!.

Once you have done this a few times, you will get a sense of how much tab you need to use and how to most effectively apply it. From my experience, and example could be: running at idle, tab full down, push to 2000RPM, once settled push to 2500RPM and give 3 seconds of tab up.. then throttle to 2800 with 1 second tab up.... then tweak tab up or down based on whatever works best for current wind / wave conditions.

Also, hard to describe the feeling, but you will actually FEEL the boat is running more free, and not fighting things when you have it dialed in. If you are dialed in to what is going on around / under you, you can actually feel the difference between smooth running (floating on a cloud) ride vs the boat fighting it.

Desired running angle is a factory / design concept. What is right for you depends on how the boat is loaded, where the weight is, if there is any water absorption in the hull, etc., and the older the boat is the more likely previous owners or you have evolved the boat from factory specs. The best running angle for you depends on your what has happened with your boat over the years, not factory specs.

B Side:
If someone has done some really bad things like adding hundreds of pound forward, or aft, that throw the whole balance off, you may not be able to adequately compensate.

+1

Really well stated !

RWS

[El L Sea]

200 feet of chain and a bigger anchor cured our need for trim tab use.

Have posted on this subject a couple times before, but I don't think you really need an inclinometer...

Bring the boat up to a certain RPM (that is good planing speed), you can play with the tabs to find the best running angle. Don't mash the tabs, just tap them a half second or so at a time. Up or down, just adjust the tabs a hair at a time and see what it does for RPMs and speed. The boat's response will not be immediate - do a tweak and wait 5-10 seconds, and see what happens, then tweak up or down a bit more. It takes time for the boat to respond. Best running angle is whatever ends up giving you best speed for a given RPM. You may find you can hit an RPM, trim for best speed, then throttle back for the speed you want!.

Once you have done this a few times, you will get a sense of how much tab you need to use and how to most effectively apply it. From my experience, and example could be: running at idle, tab full down, push to 2000RPM, once settled push to 2500RPM and give 3 seconds of tab up.. then throttle to 2800 with 1 second tab up.... then tweak tab up or down based on whatever works best for current wind / wave conditions.

Also, hard to describe the feeling, but you will actually FEEL the boat is running more free, and not fighting things when you have it dialed in. If you are dialed in to what is going on around / under you, you can actually feel the difference between smooth running (floating on a cloud) ride vs the boat fighting it.

Desired running angle is a factory / design concept. What is right for you depends on how the boat is loaded, where the weight is, if there is any water absorption in the hull, etc., and the older the boat is the more likely previous owners or you have evolved the boat from factory specs. The best running angle for you depends on your what has happened with your boat over the years, not factory specs.

B Side:
If someone has done some really bad things like adding hundreds of pound forward, or aft, that throw the whole balance off, you may not be able to adequately compensate.