There's been lots of talk about how trim tabs can improve performance, particularly with underpowered set ups. I thought I'd start a new topic to discuss sources for these and the results of the installation. My solution was to install "Smart Tabs" on my GTR 23 stock 16' cypress skiff. It helped tremendously. The major leaders in trimtab production and sales are Bennett and Lenco , and they are hydraulic and electric configurations, respectively. The Bennett hydraulic tab set up really does not lend itself well to small boat installation because of the need for a hydraulic reservoir and tubing. The Lenco products use electric screw actuators encased within the device outside the hull, a better solution in my opinion. I've had experience with both hydraulic and compression tabs (Smart Tabs) and I prefer the Smart Tab solution for small gator-tail like boats because they are easy to install, automatic, and very light. No electric or hydraulic involvement and no through hull installation. The Lenco product may work well, too, but I have no experience with them and I suspect they are much heavier than Smart Tabs.

I put the click on yore trim-tabs .... and I mite say .... I'm impressed !!!! Just thank 'bout it ... automatic trim-tabs. I believe that thays diffently gots an application fo some folks .. and I also believe that I would have 'em tore off befo I would ever find out how thay even worked on mines hull.

I'm not puttin' the knock on 'em at all ...... I'm just typin' the fact that I live in a stump field that has lots of timber and fish and stobbs and frogs and ducks and debrie ........ the other evenin' I even put a smack on an ole frigerator !!!!!

I know what you mean. But I've hit some pretty nasty stuff myself, even holed my boat. The tabs are made of composite plastic and are very flexible and forgiving. In mud the only problem I had was reversing because they remain in the down position, so I use a bungee chord to pull them up level with the bottom...works like a charm. There's an accessory one can buy to hook them up so they stay level, but the bungee is the cajun way.

So how much speed did you pick up? I know they also improve handling on most boats. With these slick bottom mud boats I imagine they would decrease the sliding in turns, which is good or bad depending on who you ask. I'm new to mud boats, but I run airboats a lot. The airboat I run has a single Lenco trim tab in the middle of the boat. It works great to stop the porpoising in deep water, but when running skinny you have to remember to lift it or no more trim tab.

Nathan

Improve hole shot and probly 4-5 mph improvement because of better planing attitude. Without the would have to go with more raw power to accomplish same. My boat is relatively narrow at widest beam and narrows further towards transome so not max area for planing but turns on a dime. If I build another the hull would not narrow to stern, but that sure looks pretty. So the trim tabs were a god send.

Well, I experimented further by substituting adjustable turnbuckles for the stock compression trim tab brace. The
turnbuckles slipped right in the brackets for the SmartTabs. After making adjustments based on many performance runs in the bayou in my back yard, my son was able to hit 3520 Rpms at 23mph down stream on my 16' cypress shiff with stock GTR23. Hhe load was: 215lbs son, 6gals fuel, trolling motor w/out battery, no ice chest.. Almost bare hull. On The solo runs i did with my weight at 249 I could only muster 19.3 to 21.6 mph. With both of us getting on plane was slow process and we managed Only 16 to 18. So with dog, decoys, boat blind, guns, Gear, my son and I , one would guess 13 to 15 mph max. The fixed trim tabs made a big difference in planing attitude. Boat runs very flat whereas before it ran somewhat bow high. The compression tabs were unable to tame porpoising like the fixed tabs did, but the hole shot with the compression tabs was better because they start out in the extreme down position and come up as speed increases, but are too loose to handle porpoising. The ideal solution would be electric tabs which are fully adjustable. When I observed the angle of the tabs after loading on trailer, I was suprised to notice that they were only slightly angled downward in relation to the bottom. I would deduce from this experiment that bigger trim tabs would increase speed and probably in linear proportion to increases surface area, at least to a point where drag coiffficients overwelm the benefit of more surface area. I think the only thing Noe that would improve hole shot and top end would be more power, but without increased weight of bigger engine. Hence,engine mods are in order.

Your comments would be greatly appreciated.

Currently installing new, larger fixed-stainless trim tabs from Bennett, without the hydraulics. They are 12" x 12". Unbelievable fortuity in that the shaft and belt housing clearances are perfect...to withing 1/4 inch at closest point. They are heavy, however. Securing them with a stainless turnbuckle I bought at Grainger supply. Fashioned my own attachment point to the tabs using combination of pad eyes and bolts, so I didn't have to drill any holes. We'll see if these improve performance even more than the smaller 9' x 10" tabs took off. If I can get up two or three more mph's with the increased surface area, I might fore-go building my own custom pods. All I'll need to do then is mod the engine with new carb, heads and exhaust if I'm adventurous enough to then risk some future reliability.

The only concern I have is that the attachment point on the tabs sits high, about 3 inches above the top surface of the tab. The flow of water coming around the transom might intersect it and create drag. If so, I'll have to fashion foils around the transom edges to direct the flow straight back and around. We'll see what happens. I should be able to make a test run this evening and report to ya'll my results.

I'm new to mud boats, so bear with me. Is it your objective to improve performance by increasing wetted surface, or by adjusting trim? If trim is the only issue, you may want to take a look at the Volvo QL tabs. They may also be a reasonable solution to some potential damage issues as well.

If you want to do both, adding custom pods with recessed tabs may be an alternative. I've got a boat with Bennetts and one with Lencos (neither are mud boats), they each have their advantages. For a mud boat, I'd go with Lencos. They are fast, self contained, simple and reliable.

I looked at the Volvo ql tabs just now. I think, but it was not clear to me, that this system involves a exposing a small tab vertically into the water versus traditional tabs which extend horizontally. Drag would be an issue for under powered skiffs like mine. I can see the allocation working well to improve planing attitude where power is not the issue, there is enough of it to offset drag. In my case I'm looking for more surface area and improved planing attitude as added benefit. The recesses tab within a pod is an interesting concept..can you post a link to a manufacturer? One off construction of it would be very difficult. My idea was to build pods that adjusted just like trimtabs. So I bought these larger tabs with the intent to construct over them the pods. I'm trying the larger tab alone first to see if I will even need pods.

Sorry no links, it would have to be one off. I think I am following you now. If you constructed (or had fabricated) a set of pods, tapered on the side where they meet the hull to facilitate negative trim, a piano type hinge to fasten it to the hull at the bottom, and with a rail welded to the top that matches the rail in a trim tab, you could mount the acutator on the transom and actuate the entire pod, just like you would a trim tab.

Petrel, you've got the idea. I though it would be too difficult to construct a pod with the hydraulic piston going right throug it to attach to the tab . So my idea became attach the turnbuckle (hydraulic piston) to the top of the pod and secure the pod to the trimtabs so that they move together. You'd have to have a pretty tall transom to accommodate the lenghth of piston or get lucky and one might fit just right. But with turnbuckle instead of hydraulic or electric piston there is a great variety of lengths available.

New tabs are installed. Will test run tomorrow and report

Best of luck with the test run. I think the "trim pod" idea may work. If a short pod were fabricated and used instead of the tab, you'd get the durability and surface area of a pod, with the instant adjustment of a remotely actuated trim tab. This link ( http://www.lencomarine.com/universal/tr ... allat.html ) takes you to a diagram on Lenco's site for one of their smaller actuators. It shows that it takes 11" of transom height to work, but I believe you could flatten the angle and shorten a pod (or recess the track) and make it work.

Just in from first test run with new trim tabs. Here are the before and after comparisons:

Before:
Solo 249lbs, trolling motor w/out battery,6 gal gas, 9" x 10" tabs

19.3 - 21.6 mph

After:
Solo 249lbs, trolling motor with battery, 12"x 12" tabs
22.5 - 23.9 mph 3380 rpms

Without trolling battery Would have probably gained .5 mph so I'm real happy with the result. With pods probably would improve hole shot but might sacrifice top end if not designed and constructed as to account for turbulance and flow. My concern with the wider tabs was their effect on the prop and potential for cavitation but this did not happen...there was clean flow over prop.

the boys thinkin out the box. sounds like its workin out.

looks like it was worthwhile. good job!