My latest expensive project (Tabs): A frustrating ordeal

[grouperjim]

Chit happens......and I did the best I could given the advice I had. Right now, my Sawzall and I are trying to make lemonade out of lemons.......check back tomorrow (Sunday) for the pics. :?

 

[Bryan 2530]

Uh oh............Sawzall Jim strikes again.

 

[Capt. Ronnie]

I took the skill saw and sawzall to my new downeast yesterday !
Maybe I'll post some pics when i get the chance.

 

[Megabyte]

Here's hoping you made lemonade...

 

[esfishdoc]

As long as you have most of your fingers you should be OK. :lol:

 

[grouperjim]

"As long as you have most of your fingers you should be OK."

Believe me, there were times during this ordeal that I would have gladly given up a pinky finger to make it all go away.......well, at least half a pinky finger.

OK, here goes the story..............

When I first got my boat I read up on trim tabs and pretty much followed the advice to get the biggest tabs that will fit within guidelines posted by companies like Bennett and Lenco.

Essentially, for single engine outboards, their guidelines say no closer than 8 inches to centerline. So, I figured I'd get the 24x12 Bennetts which put me at 16.5 inches from centerline.

Chop Chop made a post about tabs/mounting location and which size to get. So, I shot the following video of my tabs for him to show him how the disturbed water coming of the inboard portion of the blade actually converges inward towards the prop. This is something I really never checked since I installed them.

http://www.youtube.com/watch?v=lnxvCqP8RaU

I was kind of shocked to see how close the disturbed water was coming to the A/V plate. Apparently, the 8 inches from centerline guideline published by the tab companies does not take into account the set back created by a bracketed motor. You think they would have a diagram and special guidelines for bracketed boats.

Wanting to move that disturbance away from the A/V plate, I contacted Bennett who suggesting buying the 24x12s with the down fins bent onto the edges of the blade. Great, an expensive but easy solution I'm thinking.

I get the 24x12 down fin blades, and on they go....no sweat. Take the boat out and I get rooster tails shooting up both sides of the boat caused by the down fins. I call Bennett and the response is that the fins are not aligned with the running surfaces of the hull. They say I need to run a straight edge off of a strake to determine the hull running surface angle. No problem.......and sure enough the down fins (perfectly perpendicular to the transom) are a few degrees off with the hull running surface (1 inch per foot of chord).

So, the factory bent down fin 24x12s are a no go, so back to WM they go. Bennett sends me some bolt-on down fins that can be mounted in alignment with the hull running surface. So far everything makes sense to me regarding the whole running surface issue. So I take my existing 24x12s to the welding shop and have them welded in place at the precise hull running surface angle.

The tabs looked great and I was excited to get them back on the boat and get on the water. The excitement didn't last long as a new and slightly different rooster tail shot up each side of the boat.......additionally a bunch of weeds had collected on the down fins. A REAL BUMMER to say the least.

So now I had to make some lemonade out of some lemons. The down fins had to go, so out came the Sawzall and ginder with a little help from a dremmel.

Now I have some custom Bennett blades. I decided to taper them which is the same taper the original Lencos had which coincidentally align with the hull running surface.

The last two pics are my dry fit of the the new tabs......ran out of daylight. Also need to trim the hinges to length. You can see from the pic that the disturbed water coming off the inboard edge should clear the A/V plate better, and also that the tabs are cut so the inner edge angle matches the hull running surface (strake). The new blades are 20 inches at the front edge, and 18 inches on the back edge.

 

[esfishdoc]

Interesting.....

I've never thought about the "disturbed water". I have the 30 X9 Bennet tabs and there is definately a different flow of water and spray with significant deployment, but judging by all other performance parameters.... speed, rpm, mpg readouts.... I never felt there was an issue... especially since gas mileage improves with some deployment.

Richard

 

[Megabyte]

And the Admiral thinks that I'm a tinkerer...

You do some nice work Jim.
I'll bet Parker R&D loves you! :wink:

 

[cbigma]

...So we got a big weekend coming up.... plenty of time to get a feel for how the new GrouperJim "Tampa Tapered Tabs" perform. Keep us posted on the results. 8)

 

[DaleH]

I've never thought about the "disturbed water".

I use the 24x9 Bennetts and don't get any adverse effect near the OB. I often wished I went to the 30x9s and like Richard, I doubt there'd be any significant effect.

Sounds to me like the bent-down fin option was the solution to a problem that doesn't exist ...

especially since gas mileage improves with some deployment.

So true! I've been trying to tell people that for YEARS! With tabs, I can easily dial in a 10 to 20% improvement (in miles per gallon) over the non-use of tabs.

 

[grouperjim]

Actually, the fins did clean up the water around the prop.....moved the inside tab wash outboard about 4-5 inches. The hull damn near came up on plane instantly due to the increased efficiency (30% according to Bennett). Just couldn't handle the weed build up on the forward edge and the upwards rooster tails in the wake.

For me it is easy to determine what effects different modifications have on my hull because my fishing buddy has the exact same boat which we often run side by side. In my case, he still has the factory 12x12 Lencos and I replaced mine with the 24x12s. In certain follow seas, my prop would ventilate and his would not which was attributed to the inboard tab wash of 24x12s confirmed by the video. Was not a big problem operating in most conditions, but was an issue none the less that could use some improvement.

I am hoping my new custom 20 inch "Tampa Tapered Tabs" tabs do the trick. Remember too, that your 25 hulls are a foot wider and also a mod v which changes the dynamics of the hull/tab wash completely. Also a tab with a 9 inch chord is further from the prop which will allow the wash to settle a bit more than a 12 inch chord.

FWIW I am willing to post up my successes and failures for others see and learn from.

Lessons learned here: Were the down fins on a 24x12 a failure? Absolutely. Are stock 24x12s on a 2320 a failure? No, but in hindsight, I think the 24x9s or 18x12s would be a better choice due to the proximity of the tab edge to the prop.

 

[cbigma]

FWIW I am willing to post up my successes and failures for others see and learn from.

....and for that we salute you. The ClassicParker KnowledgeBase grows larger each day through the generousity of members willing to take the time to document and share their trials and experiments. 8)

Thanks for Posting and sharing with us..

 

[esfishdoc]

Actually, the fins did clean up the water around the prop.....moved the inside tab wash outboard about 4-5 inches. The hull damn near came up on plane instantly due to the increased efficiency (30% according to Bennett). Just couldn't handle the weed build up on the forward edge and the upwards rooster tails in the wake.

For me it is easy to determine what effects different modifications have on my hull because my fishing buddy has the exact same boat which we often run side by side. In my case, he still has the factory 12x12 Lencos and I replaced mine with the 24x12s. In certain follow seas, my prop would ventilate and his would not which was attributed to the inboard tab wash of 24x12s confirmed by the video. Was not a big problem operating in most conditions, but was an issue none the less that could use some improvement.

I am hoping my new custom 20 inch "Tampa Tapered Tabs" tabs do the trick. Remember too, that your 25 hulls are a foot wider and also a mod v which changes the dynamics of the hull/tab wash completely. Also a tab with a 9 inch chord is further from the prop which will allow the wash to settle a bit more than a 12 inch chord.

FWIW I am willing to post up my successes and failures for others see and learn from.

Lessons learned here: Were the down fins on a 24x12 a failure? Absolutely. Are stock 24x12s on a 2320 a failure? No, but in hindsight, I think the 24x9s or 18x12s would be a better choice due to the proximity of the tab edge to the prop.

What you say makes sense. I'm glad you pointed out yours is a 23 foot...

Good Work!

 

[TheOtherLine]

Great Job explaining the pros and cons. Sometimes stock is stock for a reason.

I wonder if that's why Parker went with the recessed tabs idea. I just never seem to have had any problems with the stock lencos. Maybe I don't know any better. Sometimes ignorance is bliss.

PS: Who was navigating while you were taking the video? Admiral?

 

[grouperjim]

Success. The second pic is the after shot. Meaning after I trimmed my stock Bennett 24x12s down to 20 (front edge) and 18 (back edge) for that "Tampa Tapered Tab" which matches the hull running surface angle. Very happy with the results. No spray and tab wash from the inside edge of the tab blade is now ample distance from the prop and A/V plate.

Had a great Memorial Day weekend. Never had the boat this heavy.......1000 lbs of fuel, 6 adults, two children, grill, two coolers full of ice, drink and food.

Before:

After:

 

[esfishdoc]

Great Job explaining the pros and cons.

....PS: Who was navigating while you were taking the video? Admiral?

You mean we should have someone navigating while taking photos in the cockpit running wide open?

 

[grouperjim]

She was navigating straight and narrow through the channel markers.........but upon returning to the helm she had napped out on me. :shock:

Not everyone is so enthusiastic about Dad's projects. 8)

FWIW it was 92 degrees that day and for those non-PH owners who think the PH is hot; pic 2 shows that the PH is the coolest place on the boat when the windows are open.

 

[Parkerman]

Love the picture of her napping. My 2.5 year old zonks out as soon as I hit the throttle. 8)

 

[Wicho]

Cool thread!
Good to hear you keep improving the boat.. My 2 year old... falls asleep practically when I start the boat!

I'm still looking for the 34' thread... anyone seen that ?