Trim tabs

Capt. Jim · Post by **Capt. Jim** » Sat Jan 24, 2004 12:33 pm

Hello, everyone. We have a 33' Sportfisherman, "HOT ROD BLUE", and we're trying to get her ready for the spring fishing season. We had one of the trim tab hoses come loose at the tab, and we want to get it fixed, of course. I noticed that the tabs on our boat are only 12" x 8". The documentation from the trim tab manufacturer indicates that the tabs should be 40" x 8". It's obvious to me that 12" trim tabs are not big enough to lift the stern of the boat out of the water enough to get her on plane. We want to go to bigger tabs. The tabs on our boat are mounted on the BOTTOM of the hull, not on the transom. There's a chine in the way that would hinder putting longer tabs on the boat in this manner. I'm speculating that this is the reason Bertram installed undersized tabs. (It was too much trouble to mount them correctly.) We obviously have to mount the tabs on the transom, with faring blocks to componsate for the transom's curvature. Has anybody done this? Any tips or hints? Thanks. Capt. Jim Bost

lobsta1 · Post by **lobsta1** » Sat Jan 24, 2004 4:26 pm

My B33C came with 9x18 tabs mounted on the transom. I upgraded to 9x30 Bennet tabs. Cut a block of teak to match the curvature, then bolted the new tabs to the blocks. Have a swim platform & had to cut a small triangle of the bottom corner to allow the tabs to clear. Spoke to Tom McGow head of customer service at Bennet, & he recommend dual pistons for over 30" tabs. Reason being the chance of breaking the hinge pins on hard backing down. It was to much trouble clearing the platform brackets & steering arms inside, so settled on the 30" tabs. The 30's make a big difference over the stock. As far as your SF, I believe they are bottom mounted so they won't snag a fishing line. If you're a hardcore fisher, then you are already aware of that issue. If you decide to go this route, the bottom of the hull is NOT a straight line. It has a convex shape. You will have to do a balancing act on where you place your tabs across that curve. Good Luck Al 1978 33 FBC NITES OFF

Capt. Jim · Post by **Capt. Jim** » Sat Jan 24, 2004 11:19 pm

Thank you, Al. I think I'll haul the boat out and have a look. Jim

Sean B · Post by **Sean B** » Mon Oct 18, 2004 6:39 am

hey lobsta1- have any pics of the tab installation you did? I'd like to see

lobsta1 · Post by **lobsta1** » Mon Oct 18, 2004 3:30 pm

Sorry Sean, no pics available & I'm staying in the water until a short haul next June. It's not really that difficult. Biggest problem is trying to get both sides evenly mounted on that convex section. It really helps to have a second pair of hands available. Al 1978 33 FBC NITES OFF

Post by **dougl33** » Tue Oct 19, 2004 10:41 am

I feel I must add that I have operated these boats with both the stock tabs as well as aftermarket "over-sized" ones. I have the original 12x8's on my 86 FBC and my friend has much larger after-market tabs on his 88 FBC. I'm not sure of the make or size of his tabs, but they are huge compared to mine. After spending several hours operating his boat on the ride from Maryland up to Mass, I can say that his boat is much less responsive to helm input than my boat. It also seems to be squirrelly (sp?). The bottom line is that I had been tempted to out bigger tabs on my boat until I spent some time at the wheel of a boat with the bigger tabs. I would not change the size of my tabs and after the back to back comparison, I once again came to the conclusion that Bertram knew what they were doing when they built these boats. Maybe the SF's would be different. Just my .02 cents. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth

TIM · Post by **TIM** » Thu Oct 28, 2004 12:39 pm

DONT BE SCARED TO GO BIG. I JUST PUT ON 36 x 12 TRIM TABS. I HAVE A SWIM STEP " FOR THE KIDS" SO I DON'T HAVE A PROBLEM WITH MY LINES GETTING CUT. I CAN'T TELL THOUGH HOW MUCH THESE TABS LET YOU TAKE ADVANTAGE OF THE BERTRAM HULL IN CHOP. AS WELL I HAVE PICK UP BETTER GAS MILLAGE AND A BITCHEN RIDE @ 18 TO 21 KNOTS. WOW.... THE ONLY DOWN SIDE IS YOU CAN GET TOO MUCH TRIM AND STUFF THE BOW GOING UP HILL IN LARGE SEAS.

RobB · Post by **RobB** » Sat Oct 30, 2004 10:33 am

Capt. Jim, I recently replaced the leveler tabs on my '87 SF with Bennett 42x12 trim tabs. I too had a hose begin to leak, and wanted to have a means of pitch control at lower speeds. It is my understanding that the original tabs were intended primarily to offset the lateral instability inherent in a deep-v hull, thus the small size. As mentioned by Dougl33, Bertram got the hull to set the ideal running angle on its own at published cruise speeds with the stock tabs retracted. I am usually not in a hurry to get anywhere, so a 20 knot cruise and the associated fuel burn seemed unnecessary. To install I applied a 42 inch contoured filler strip to the convex transom to create a flat surface for the new tabs. This filler turned out to be about 1 inch thick on each end, .5 inch in the center, and 2" wide. The modified V hull is curved along the bottom also. This required the tab bottom to be flush at each end and about .5 inch above the bottom in the center. The stock tabs are attached to the bottom of the hull in a 12x3 inch recess .4 inches deep. This area falls near the center of the new tab. If left unfilled it has the effect of smoothing the transition between the mismatch of hull and new tab. The 42x12 tabs arrived with a single actuator. This is more than adequate for the trim loads imposed on them, but if I had to do it over I would have installed two on each to slow down the response time. They are extremely effective. It had been recommended by some that twin actuators would also lessen the possibility of damage when backing down. Having sheared the hinge pins while backing down under low power, I expect that more than another actuator would be needed to solve this problem. The Bennett representative I spoke to after this occurrence was very supportive. He immediately sent out a new set of hinges and pins without charge. His recommendation was to install either their optional telescoping stops or a pair of transom to tab cables to limit extension. I intend to do the latter at next haul out. Be advised that when using single actuators, the pipe nipples included in the kit may interfere with the rudder arms if not cut down. I have experienced no significant changes in handling or steering response with these tabs. It is easy to over trim at any speed now, but the advantage is that I can choose any run angle at any speed — especially useful when facing steep chop. As others have observed, this hull is happiest at around 20 knots with the stock tabs. I find now that I can consistently gain an extra 2 knots for a given rpm (or a reduction in power for given speed) A Floscan/Twinscan was installed after the tabs, so I don’t have precise before/after comparison figures. I find that the best range speed with new tabs is around 15-16 knots at .75-.85 nautical miles per gallon with stock MIE 340’s and 22.5x24 three blade props. Depending on conditions, this equates to about 2500 rpm. 3150 rpm yields about 20 knots at .55 - .65 nmpg. The twinscan system references SOG using GPS input, after making a number of observations this seems to be the average factoring tides, winds, fuel burn-off , wave condition, etc. I have found the optional digital trim angle display to be quite useful. The sensors were pre-installed when purchased with the trim system. Regrettably I chose to install the standard “joystickâ€� type control switch included in the kit. While intuitive in application, it lacks the precise feel and response of the dual on/off switches available as an option. When I find time I will re-install the dual toggle switch that controlled the original system. Good luck.

Jose Jaen · Post by **Jose Jaen** » Thu Sep 15, 2005 5:16 am

Dear Friends; It has been my impression that the trim tabs (12 inches) are undersized for the 33FBC with 3208T specially when loaded and under heavy seas. I was wondering if your previous discussions about installing larger tabs have changed. Thanks. Jose Jaen "Blue Chip" 1993 33FBC Miami FL

photo finish · Post by **photo finish** » Thu Sep 15, 2005 7:35 am

On my boat,I feel that my boat runs best with no tab at all.I only use the tabs to balance the boat port to starboard due to weight shifting.(which on a boat this size i am surprised how people moving around affect the balance so much,but i guess that is due to the deep v .) when i add too much tab i find that the boat gets a little sloppy. So would bigger tabs help the handling or do nothing on my boat? I do not know for sure but at this point i feel the stock tabs 8x12 work fine and feel there are other projects that i would spend my time and money on. Not to mention the people that are adding blocking to the hull to offset the curve, does that not create a little drag? Tim Stamm Photo Finish 1981 33' Bertram FBC

captgene · Post by **captgene** » Thu Sep 15, 2005 7:44 am

Jose, I still get comments on the size of the tabs. I was hauled out a couple weeks ago and heard the same thing. I also noticed while in the yard there were 4 31s in various stages of total refit, 1 38 was in there too. All had "huge" tabs compared to the 33. Beats me what Bertram was thinking. But anyway, I travel the same seas you do. When it's big and I'm going into it I slow down and go full down on the tabs with no trouble. Seas from any other direction I pretty much get off them completly. This is when I have the boat totally loaded down. I'd be interested to see what bigger tabs would do, but have never considered replacing the little ones. Gene Dugan

Post by **dougl33** » Thu Sep 15, 2005 7:48 am

Tim, I think that's because you cruise at a higher speed than most of us. I've said it before and I'll say it again, that these boats don't need any tab when you're moving at 20 knots or more, other than to balance an un-even load. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA

Gunny · Post by **Gunny** » Fri Sep 16, 2005 12:51 am

Doug, I have to agree with you! I never use my tabs Gunny

sbeer · Post by **sbeer** » Fri Sep 16, 2005 3:13 am

i USE MINE FOR LOAD ADJUSTMENT ONLY Mike Lawrence 81 sportfish 33' shot'n'beer

Post by **Admin** » Fri Sep 16, 2005 4:33 am

I use mine anytime sea conditions cause me to lean either to port or starboard. They straighten her out nicely. David Sumich 33 Megabites Huntington Harbour, CA Forum Administrator