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EricG
05-23-2006, 03:54 PM
Compared to some of your restoration and modification projects, my little tab install won't seem like a big deal, but to me this was a pretty big undertaking. Drilling holes in the transom of my 18 was very intimidating. I decided to post a few pics for anyone else that may be considering adding tabs...it really isn't difficult. Now I just need to find some sun so I can try them out.
1. Before
2. The Kit
3. Tab Mounting Holes
4. Tab Mounted
5. Positioning the tab making sure it didn't interfere when retracted (1.25").
6. Installing the Actuator
7. Outside install Complete
8. Pump Install - On the Bulkhead - Outside the Port Stringer
9. I decided to remove the compass on my dash and replace it with the rocker switch. This is the before pic.
10. I had to build a plate to cover the 4" Gauge hole where the compass was, I don't have much more than a drill, hacksaw, and tin snips, so the metal work is a little "rough".
11. The finished switch install - I'm not totally happy with it, but until i can get something better built - it'll have to do.
I can't wait to try them out, it may not be drive trim, but it's a start :smile:.
EG

Carl C
05-23-2006, 04:12 PM
It always takes a while to get up the nerve to get out the cutting or drilling tools. Looks good. You're gonna love having those tabs.:lifeprese

EricG
05-23-2006, 05:55 PM
OK, you're gonna hate me for this, so I may as well get it over with: NICE installation, but the trailing edge is too low..
We can fix it in 4 minutes at the first event I see ya at tho :) :) :)

OK...I've got to know...how high should I have gone? I went up just over 1/2" on the leading edge, and about 1.5" on the trailing edge? I seem to remember some post about removing some sort of stopper on the actuator, is that what you are referring too?

Hmmm...hopefully someday not to distant I will have that opportunity to get the boat to a gathering down there...but with fuel prices the way they are...it'll have to be a 1-way trip :rolleyes: :biggrin:.

Thanks for the kind words...

EG

MOP
05-23-2006, 08:54 PM
I don't agree 1.5 at the trailing edge should be fine, will some water hit them yes but they will be out of the main flow. You can get them to run cleaner if need be by squaring the trailing edge of the transom. You know how fast you were before you will know if you have any speed lose I doubt it. Run it and let us know!!

Phil

DonCig
05-24-2006, 12:23 AM
Eric, there is an easy way to find out which of the 2 experts called this one correctly. The old classic A/B testing routine.
Before you start cutting off 1/2" or 1" on your actuator piston rods, do this very simple and effective test.
Run your boat at 3,000 or 3,500 rpm trimmed out with the tabs fully up and measure your GPS speed on a very difined straight stretch of water with your drive set all the way in or adjust your drive limiter switch to a setting that will stay contstant for this test. We need to make sure that the drive is in exactly the same position each time. I have Gaffrig mechanical trim tab and drive tab indicatiors and they can read a full (1) number off depending on whether I am lowering the units or raising the units. A straight edge works great if nothing else is available.
Now unscrew the two stainless steel philips screws from the bottom of the actuators and tie a heavy nylon cord through the screw holes in the tabs and tie both the the tabs "UP" in an exagerated manner. Now go re-run the exact course with the wind and waves in an identical pattern. It should not take more than 20 minutes to perform this task.
Measure your GPS speed. Do this A/B testing again at maximum speed.
You will come to a very easy decision as to whether your tab placement and trailing edge location is costing you any speed. It has been my observation that not enough testing takes place in these discussions before new holes are drilled or actuators are shortened.

Good Luck,

Don

p.s. - nice workmanship.

Formula Jr
05-24-2006, 05:18 AM
Pic 9: Southwest end of Mercer Island? :biggrin:

Good choice getting the rocker switches instead of the joystick.
Did the kit come with the interrupter relay or is that built into the
new style rocker switches?

http://www.bennetttrimtabs.com/partprice.htm#Interrupter%20Relay

With the rocker and the racing style bennett switches the motor will blow a fuse if you accidently press one switch up and the other down at the same time.

Also, you might want to add a retainer so the motor/reseviour can't
slide up out of the transom mounting bracket.

You will notice the lack of side to side rolling immediately.

:dolphin:

EricG
05-24-2006, 04:12 PM
We need to make sure that the drive is in exactly the same position each time...

That shouldn't be a problem...this attached pic shows my trim setup :biggrin: :biggrin: (note: that pin will be moving out now that I have the tabs installed:wrench: ). Thanks for the great testing methodology....I just need to head out to my private testing area "Lake G"....at only 2 miles long, and very little weekday traffic, I don't have much trouble getting good back to back testing results.


Pic 9: Southwest end of Mercer Island?


Close....about 5 miles north, right in front of Mr. Microsoft's house :biggrin: We really do need to revive the scramarama this year.

Not sure on the relay, I'll check with Bennett about the switch I got.

BTW Jr., we were very excited about our mail on Saturday....it's on the calendar :beer:

Thanks all for the input.

EG

billy22zx
05-24-2006, 04:49 PM
On the subject of trim tabs...i had my 22 in the water last weekend for the first time,and not quite figured out the trim tabs. The switch on the dash shows "bow down" when pushing up on the switches. Am i correct that if the bow goes down...the tabs go up? Tabs down mean bow goes up? Or visa-versa. It`s all so confusing. :bonk:

wannabe
05-24-2006, 04:56 PM
tabs down -----bow down

BigGrizzly
05-24-2006, 09:34 PM
Sorry don I don't agree on your test! None of my boats have a problem at that speed. the point in question is at wot. I gained a minimun of 2 mph on one and a max of 4 on another. I have had Donzis ever since 1966 and still have them. The rule of thum is 10 degrees minum lift. if they drag even a little the handling and speed are affected. Just look at a real race boat and see how they are set up. My Criterion's are still too low at least untill tomorrow when i do trick #2. remember ypu can always put them down if they are too high

MOP
05-24-2006, 10:24 PM
The "Smack Master" gets to carried away with the Techy way!!! Like I said you know how it ran, if it runs tha same with the tabs up point proved!

MOP

EricG
05-24-2006, 10:26 PM
I have dug up the old Mod thread for anyone who doesn't remember:

http://www.donzi.net/forums/showthread.php?t=33672

As far as the answer...I do know what I got out of her last year, and this is the only change I've made, so the first run should give us the answer. Of course, it's supposed to be under 60 with rain all weekend:kaioken: :kaioken: .

EG

DonCig
05-24-2006, 11:37 PM
Randy and MOP, I respect your opinions and common sense when it come to your life experiences with a large number of boats, including Donzis. Why don't we ask a Bennet engineer or Mercury engineer that have some actual test data done under controlled conditions. I believe that Madpoodle may have done this work a few years ago. Better than that, lets add to the value of this site by doing some of our own product testing. Randy, you may be correct that in most situations a minimum of a +10 degree rise from horizontal is a safe and fast choice, but I assure you that any general number like this was derived from methodical and logical testing and not only life experiences. Which includes racing input. MOP, you may also be correct that where the tabs are currently located could be perfect. That is why we test.
And if you are courious, I spent many years as a program manager at a product testing laboratory. We spent our days putting scientific facts behind old aged wisdom. I can say that I have tested everything from seat belts for GM to chain saws for Black & Decker. Would you like for me to tell you how long it takes to cut your hand off with a mis-guided chainsaw?

By the way, neither one of you is any older than 35. I met Grizzley this weekend and he can not be a day over 30.


Sincerely,

Don

p.s. - I am from Missouri. (The Show Me State).

Lenny
05-25-2006, 02:19 AM
I met Grizzly this weekend and he can not be a day over 30.
Sincerely,
Don
p.s. - I am from Missouri. (The Show Me State).

Nice to see you on the mend Randy :)

Nice to see you back...

Lenny and Deneen

Ed Donnelly
05-25-2006, 03:10 AM
Don; 1.2 secs................Ed

MOP
05-25-2006, 05:27 AM
Qoute: the "Smack Master" By the way, neither one of you is any older than 35. I met Grizzley this weekend and he can not be a day over 30.

Boy do I wish! The SOB that coined the phase "THE GOLDEN YEARS" should have been shot or drawn and quartered. The real truth of the matter is they are "THE RUSTY YEARS"!!! When you are young you do a lot without thinking thats why the word regrets was invented! When you get where we got you think about everything and regretfully don't get much done!
I to did a lot of chain sawing wore a few out but can't call it testing, cut cord wood several winters for extra $$ when I was much younger and did some dock building around the same time. We use to have to do a fair amount of tip cutting for notches etc, one of our guys had one kick back and take out his jaw and almost up to his eye. Chain saws can be one mean bastard if you are not carefull. Words from the school of hard knocks and experiance!

BUIZILLA
05-25-2006, 07:34 AM
I think the 10* number is irrelevant.

Clearly, for starters, the amount of degree's is dependent on where the transom tab face plate is mounted, relative to the bottom parallel surface, the higher it's mounted, the less degree's of tab travel for a baseline. Every 1/8" difference could be 1* variance, either way. In the grand scheme of things, every boat could be different. When a hull is properly trimmed, I think the base number for water deflection off the transom will be about 6*. And, that's assuming you have no built in hook in the hull....

JH

DonCig
05-25-2006, 08:13 AM
Jim, I think that you are right on the money in your assessment
I would think that hooking up a couple of load cells to the bottom of the rams where they attach to the trim tab plate and then measuring the upward load in pounds at a given setting and speed could be enlightening. I spent a few hours this last Monday setting the tabs on my dads Cigarette; which are mounted a good .75" above the bottom edge of the boat, and with an upward angle of around +10 - 15 degrees. I found that the tabs were parallel to the last 2 feet of the bottom at a setting of 3 out of 6. At a setting of 5 out of 6 the boat would slow down and be trim sensitive. And at a setting of 6 out of 6 the boat would keep the nose fairly well planted. On this boat with these very small Keikenhaffer tabs, it is my opinion that they were mounted a little to high, yet still functional.

Don

Formula Jr
05-25-2006, 03:59 PM
"I would think that hooking up a couple of load cells to the bottom of the rams where they attach to the trim tab plate and then measuring the upward load in pounds at a given setting and speed could be enlightening." - Doncig
That is a freaking excellent Idea!
Are there load cells that would be the right shape to fit seamlessly between the ram mount and the tab? I have often wondered just how much pressure tabs are really taking.
Wouldn't pressure sender units in line with the hydrolic lines do the same thing once they are calibrated? Then you could have two small pressure gauges above the tab switches.

Carl C
05-27-2006, 08:00 PM
My tabs are 1/2 inch front and 3/4 inch trailing edge from the factory. Are they slowing me down?:confused: Anyone?............Poodle?

MOP
06-05-2006, 11:23 PM
TTT!
Well what about a speed report?

MOP

Ed Donnelly
06-06-2006, 12:13 AM
My Criterion came with 2 high pressure hydraulic gauges. The more you drove the Bennetts down, the higher the pressure. No angle indicators. When I installed the K-planes I lost the use of them....Ed

Formula Jr
06-06-2006, 03:45 AM
Regardless of what the peanut galley here says, you will never regret putting tabs on.

Even if you just leave them fixed at a certain deployment. They may cost you 1 or 2 MPH at wot, but what you gain in control of rolling is going to let you take much crazier slop in Lake Washington than you could before. And thats much more important than flat water top speed. Who the hell runs a Donzi in flat water anyway?

There were lots of summer days on The Bay when it was completely calm. And its like, why even go out? And then you just wait for the tropical storms.

:smile:

EricG
08-31-2006, 04:42 PM
Talking Donzi's last weekend at Jr's wedding made me realize that I never posted the updated results to this thread. So, here goes:

Original Tab installation: Top Speed 53.6 - Could feel it dragging a bit.

After cutting the tab stops approximately 1": Top Speed 55 - 48-4900 RPM. which is within .5 MPH of my speed without them.

I can't believe how much more stable the boat is overall with the tabs. And being able to control the porpoise makes the boat a lot more enjoyable.

If you happen to be afriad to make the mod, don't be - it's about the easiest project I've ever done. It took me longer to find a bucket to let the little bit of hydro fluid spill into than it did to actually do the mod.

-EG

realbold
08-31-2006, 08:43 PM
The only scary part is drilling holes in your transom. The way I would do it is drill all holes well oversize, make screw holes cone shaped, bigger on the inside, coat the core with unthickened epoxy, then fill the holes with an epoxy like Marine Tex, sand smooth, drill holes. Now if the bead fails the water will not get to your wood core. Use a drill guide so the holes are perpendicular.

I am doing this for all hardware that is fastened to a wood core.

Morgan's Cloud
09-01-2006, 07:56 AM
*******Top
After cutting the tab stops approximately 1": .*********
If you happen to be afriad to make the mod, don't be - it's about the easiest project I've ever done. It took me longer to find a bucket to let the little bit of hydro fluid spill into than it did to actually do the mod.
-EG
IS this the modification that MP says he could take care of in 4-5 minutes ?
How exactly do you do this ?
I imagine it allows you to raise the trailing edge of the tab without having to re-drill the transom..
What a great idea !
Steve

Pismo
09-01-2006, 08:05 AM
Sounds to me like a great installation given that you did not drill and find a gallon of water and soaked rotted wood in your transom. Everything else is minor details compared to if you had run into that. This would have been my main concern during this project.

EricG
09-01-2006, 10:48 AM
IS this the modification that MP says he could take care of in 4-5 minutes ?
How exactly do you do this ?
I imagine it allows you to raise the trailing edge of the tab without having to re-drill the transom..
What a great idea !
Steve

Yes...Post #13 on this thread has a link to the original post. As my tabs were new I didn't bother with the o-rings, so it was literally a matter of unscrewing the actuator, removing the "stop" from the mount (mine clipped in, very simple), cutting the stop, filing it smoothe, and reasembling. Might be the most effective 5 minute mod ever.

EG

margo
09-02-2006, 11:22 AM
Compared to some of your restoration and modification projects, my little tab install won't seem like a big deal, but to me this was a pretty big undertaking. Drilling holes in the transom of my 18 was very intimidating. I decided to post a few pics for anyone else that may be considering adding tabs...it really isn't difficult. Now I just need to find some sun so I can try them out.
1. Before
2. The Kit
3. Tab Mounting Holes
4. Tab Mounted
5. Positioning the tab making sure it didn't interfere when retracted (1.25").
6. Installing the Actuator
7. Outside install Complete
8. Pump Install - On the Bulkhead - Outside the Port Stringer
9. I decided to remove the compass on my dash and replace it with the rocker switch. This is the before pic.
10. I had to build a plate to cover the 4" Gauge hole where the compass was, I don't have much more than a drill, hacksaw, and tin snips, so the metal work is a little "rough".
11. The finished switch install - I'm not totally happy with it, but until i can get something better built - it'll have to do.
I can't wait to try them out, it may not be drive trim, but it's a start :smile:.
EG
Looks like you did a good job...Inoticed the ss prop is that a 250 volvo Does it go on with the locking tab and the screw on cone if so let me know the make of the prop and size....Looking for one that will fit the 250