Trim Tabs

[LandLubber No More]

Here is a pic of the trim tabs on my 67 Pacemaker. Does anyone have any clue if these are original or if a 67 Pacemaker is supposed to even have trim tabs? Do I need them?

http://www.storm.ca/~suep/Misc014.jpg

[Donn]

I've seen lots of Pace's with Bennett trim tabs. Not at all uncommon. The only way you can tell if you need them is to run the boat.

[LandLubber No More]

When I replace the Transom, is it very much more difficult to put the trim tabs in later if I need them. If I do not need them, I would rather leave them off. I don't intend to be breaking any speed records with this old girl.

[Donn]

It's not a question so much of speed, but trim, port-to-starboard, as well as fore-and-aft. My boat lists slightly to port, because of the weight of the head and galley. It's only a slight list, and she's a displacement hull, so I don't need tabs. Your Pace is a planing hull, and trim is important.

Like I said, I've seen them on lots of Pacemakers. They're probably there for a reason. Do a Google search on Pacemaker, and then search within results on "trim tabs" You'll see what I mean.

[John E Hardiman]

Originally posted by Donn:
The only way you can tell if you need them is to run the boat.Donn's right, you may need to run the boat to see if you need them (and most likely somebody thought so and went through the trouble to put them there in the first place). From here they look like the have a fair amount of angle dialed in, or are they just down against the stops? As long as you can pull them up flush, leaving them there is not a performance question (more tools to control trim always being better). Is the real question that they are broke and you want to cut costs when replacing the transom?

[LandLubber No More]

I have no idea if they work or not. I guess my real question is ... will it be easier to install them during the transom repair or after? The transom will be completely new. Also, new trim tabs where the RAM is completely exterior seem much easier to install.

[Stiletto]

If you are not worried about originality your comment about external fitting is a good one. You could install them after the transom is fitted if required after a test run or two .

[Gary E]

They do look like Bennett Trim Tabs, and if you look near the helm you should see a control stick that allows you to move either one up or down or to move both of them at the same time. Put a Battery in and try it. The boat no doubt need them, heavy boat, trying to get on plane, but since it's a single engine and by the size of the prop I am guessing it's aprox 200 HP running direct drive, no reduction gear. So, it's gona need all the help you can give it trying to overcome the bow wave, specially since that boat tends to have all passengers in the rear causing the stern to squat. The tabs actuating motors are mounted just under the deck, lift the rudder access hatch and you will see them.

Now, as for replacing the transom... Are you sure you "NEED" to?.. looking at the area near the scuppers, it may be not required, and as for the starboard side fron the 2nd step from the top up to the top of the transom, it really does not look all that bad, well.. from here anyway..

G

[LandLubber No More]

Originally posted by Gary E:
... by the size of the prop I am guessing it's aprox 200 HP running direct drive, no reduction gear.

GYou nailed it Gary, she has the original 327 Chevy small block, putting out 220 HP. Thanks for the advice, I will try the trim tabs in the near future and let you guys know the outcome. As for the transom, it looks in pretty bad shape. At the lowest point it has sprung away from the plank. It is plywood (I do not think it was very good quality) fibreglassed over. I intend to have a professional look at it and give me an opinion and a quote. I have a ready supply of White Oak so I was thinking of using that.

[LandLubber No More]

More of the damage.

http://www.storm.ca/~suep/Misc016.jpg

[brad9798]

You won't set any spead records in that boat anyway! ;)

Seriously, keep them. Even if you do not use them, it is a selling point.

And, even at 2,000 rpm, certainly blazing fast, you will notice quite a difference in performance and economy.

[Allen Foote]

Do yourself a favor, laminate cedar shakes across the bottom of you planking,at the transum, creating wedges that start 20-24" before the end of the transum and create a "flare" to direct the water flow at the end of the transum, down (I hope I worded that so its understandable) AND put those or a newer set of trim tabs back on after rebuild. These boats "squat". With thier round bilges and non-flat run aft, these boats will only go so fast......but you want the bow down when hualing A. Egg Harbor had the wedges on when new.

[ 01-18-2004, 11:46 AM: Message edited by: Allen Foote ]

[LandLubber No More]

Are you describing a sort of clapboard effect. I am not sure I understand. How does this help? (I don't doubt your advice, I just need to know why). Cheers!

[Allen Foote]

Let me see if I can explain this better...
What you want to do is epoxy wedges to the bottom of the boat so that the fat part of the wedge ends at the transum/bottom cusp. You want to use long wedges (such as 24" shims or possibly longer such as 36"). The idea is to redirect the water flow down ward (as it passes that part of the boat), thus providing "lift" to the ass end. That is the same thing being accomplished by the trim tabs. The difference is that trim tabs are "supposed" to be adjustable. That is a rarity. Most large boats that have them seem to not use them, or , leave them in 1 setting always. That being said, use the combination of both, but make sure that the replaced trimtabs are put level to the bottom of the wedges so that it is a striaght run...the water flows across the wedges-across the trim tabs without a riase up nor constricted by a too-low trimtab.
Your boat is not a planing hull. It is not designed to get "ontop" of the water. Keys to this are 1)round bilges (no distinct chines). 2) No "flat runs aft (meaning the bottom configuration is not flat from the shaft logs to the end of the transum.
From experience....these boats "squat" when you pour the power on....the transum area sinks down and the bow rises. Wedges and trim tabs counter this naturally occuring event. smile.gif

[LandLubber No More]

Now I get it. Now I understand the concept. That seems easy enough to do. I will be putting new Trim Tabs in place as the old ones are beyond repair(as well as missing a few pieces). Thanks for the advice.

[nedL]

Wedges are often times a good idea & can really help the performance. I'll make one comment though. I was taught almost 30 years ago by an old guy that used to race iboards that you really don't need to run the wedges very far forward under the bottom of the boat, he said that the extra distance only seems to create more drag. Granted I have a small 16' inboard, but the wedges I glued on are about 3/4" thick (vertical measurement), and run foreward under the bottom only about 2". I have four of them, each about 4" wide, two on each side of the rudder & spaced about 2" apart. Those wedges make a big difference. I actually started with three on each side, but that was to much & I cut the outer ones off.

[LandLubber No More]

Is there any formula for how thick these wedges should be?

[carioca1232001]

Allen Foote wrote:


From experience....these boats "squat" when you pour the power on....the transum area sinks down and the bow rises. Wedges and trim tabs counter this naturally occuring event I am attaching a photo of the "squatting" you have referred to above

http://www.imagestation.com/picture/sraid100/p1f5b8524eebe49c9d9052de71a3074b5/f9e41147.jpg

Mine´s a 1962 34 ft Chris Craft (but of Scandinavian design I was told), built in Brazil and which I rennovated over the last 5 years or so.

Had the V-8 petrol 170 HP engines replaced with 4-cylinder 170 HP turbo diesels, which obviously aggravated the problem (extra weight)

Have talked to Bennett Tabs and they said these would level the boat out.

However, this is the first time I´ve come across the use of wedges . Sounds promising, especially if used simultaneously with Trim Tabs.

Another Forumite has also seconded the use of wedges.

Have a look at the transom below and tell me your thoughts on this one:

http://www.imagestation.com/picture/sraid100/p5c22626afb5521784ae1c281450775c0/f9e41711.jpg

Thanks for your time

[Allen Foote]

Carioca,
I went to the sight

http://www.eggharborowners.org

and searched through the pictures to see if I could come across a picture of the transum/bottom area a 37' Egg. It would show the total contrast between your boat that is hard-chined and a round chined Egg. Unfortunately, I could not find one. Yes, you could definately put a set of trim tabs on that hull. Because it is bare...I'd start with a set first. Try the larger tabs, 42". Then, if you still need to improve the performance, try the wedges.

[ 01-19-2004, 07:34 PM: Message edited by: Allen Foote ]

[Gary E]

Allen,
You are correct in sugesting wedges, I had forgoten about them. But for this hard chined hull, with what appears to be plenty of clearance from the prop to the boats bottom, why not install 3/4 to 1 inch thick by 30 inch front to back wedge? Install them full width, give that a try then if additional help is needed either add another layer of wedge, or install the Trim tabs. If the wedges are installed after tabs, the tabs will have to be moved lower.

G

[ 01-19-2004, 10:51 PM: Message edited by: Gary E ]

[carioca1232001]

Allen, Thanks very much for your help.

What would the main difference be - in hydrodynamic terms or hull-attitude - between a hard-chine like mine and a round-chine as on Eggs, under full power ?

I am eager to learn a thing or two while I am at it !

[carioca1232001]

Gary, Many thanks.
You are advocating installing wedges, much cheaper and free from malfunction, compared to Trim Tabs.
Is there any extra information you would require for consolidating the the case for using wedges ?

[Gary E]

Not really much more to it, you hit the nail on the head. Low cost, simple to make and install, and if they work well, can either add more wedge on next haul out, or spend the money on the tabs. I never liked tabs as I ran off shore in a lot of bad weather. Tabs and following seas just dont make for easy steering.

G

[ 01-19-2004, 09:29 PM: Message edited by: Gary E ]

[carioca1232001]

Gary,

Seems difficult to picture a tiny 3/4" to 1 " wedge on the transom, tapering out to zero some 30 " in the forward direction, doing the job (or nearly so) assigned to Trim Tabs on a 6 ton boat.

When you say "add more wedge" if the boat does not level-out as desired, are you suggesting that the wedge be widened (to say 1 1/2 ") and /or that more wedges be installed all the way along the underwater transom ?

Thanks

[LandLubber No More]

My Pacemaker is fairly straight accross the stern as opposed to V shaped. I would think this would make the wedges more effective. Is that right or have I got the concept all wrong.

[Gary E]

"install 3/4 to 1 inch thick by 30 inch front to back wedge? Install them full width, give that a try then if additional help is needed either add another layer of wedge, or install the Trim tabs. If the wedges are installed after tabs, the tabs will have to be moved lower."

...what I really mean is the thick end of the wedge at the transom, tapering to zero thickness 30 inches forward, and that is INSTALLED FULL WIDTH on the bottom of the boat.

They are often made from cedar shingles aprox 5 or 6 inches in width, but I would make them from flat stock, mahogany, cedar, cypress, or any other good wood that works well underwater.

There is no doubt in my mind that this will help, only question is, will it be better if the wedge is more?... Run the boat for a summer, see how it works, then next year you may want to add another layer of wedge bringing the total thickness at the transom to 1 1/2 or even 2 inches total. Unless there is a identical boat that allready has this setup in your area to copy, this is strictly a trial and see what happens method.

For the Pacemaker, I would add the wedge to the flat portion of the bottom, between the "turn of the bottom planks".

I hope this makes it clear,

G

[Allen Foote]

I would try the tabs first simply because of the V bottom....because yes, the wedges are more affective on a flat run (deflecting down ward as opposed to outward). The V-bottom configuration makes for a better bite (tracking through rough water), and is what the early Bertrams designs were known for.

[carioca1232001]

Gary and Allen,

Have noticed at WOT that the area between either side of the keel and rudders SEEMS to be the only part of the underwater hull in contact with the ocean, as the rest SEEMS to be riding over it!

As a first guess in this cut-and-try solution, am thinking of installing two wedges on either side of the keel in the aforesaid area, 30 cm wide x 4 cm thick (at transom) tapering off to zero some 75 cms in the forward direction.

Will keep you posted on developments.

And many thanks once again.

[Gary E]

"Have noticed at WOT that the area between either side of the keel and rudders SEEMS to be the only part of the underwater hull in contact with the ocean, as the rest SEEMS to be riding over it!"

Not a chance, unless you have at least 1000 HP...and from the picture shown you plowing along, you dont.

Did ya ever hold your hand out the window of a car going 100 Kilometers per hour? and hold your fingers tight to play like a airplane wing?... the force acting on your hand is simular to what will act on the boats @ss end to lift it.

What you want to create is a change in direction of the flow of the water passing under the hull starting 30 inches..(762 mm) forward of the intersection of the bottom and the transom... this is the zero thicknes part of the wedge, now the thick part (25 mm) is at the intersect point of the bottom and the transom.. ALL the WAY ACROSS..from chine to chine...

Allen is corect that Tabs may be better, and a lot of 31 Bertrams have them. I personally would rather install wood wedges, several reasons...

..LOW Cost...ok I'm cheap, and I can do the work myself.

..Trim Tabs even though adjustable, and allowing different settings, I know guys that have them and never adjust them.

..Running in a following sea is easier without waves with tons of water falling on the tabs sticking out there pushing your boat deeper into the water. and making steering rather a pain.

..Do you back into a slip?.. ever see a guy get to close to a piling and the tab gits crunched?

..and the fishing line will not get cut off by the edge of the tab
So.. THE BIG ONE WILL NOT GET AWAY...

G

[ 01-20-2004, 06:21 PM: Message edited by: Gary E ]

[carioca1232001]

Gary,
That is EXACTLY why I used the term "SEEMS" ! No, you certinly have done your homework on this one !
I was tempted to install the wedges right away, took all relevant measurements this morning..... but it is summer now and other refurbishments initiated in mid-November are nearly done.
Family and friends are putting on the pressure to see the boat in the water - get me ?

[mmd]

Please note whilst you all charge towards adding wedges to the trailing edge of your boats' planing surface that in addition to acquiring lift in the stern, you are paying for it with increased drag. The stern will come up, but you will go slower.

Trim tabs, while costlier and mechanically more complex, have the advantage of being easily adjusted to optimum angle, and, if hydraulically activated, able to be adjusted to suit changing conditions of use and even withdrawn from effective use completely, thereby reducing drag caused by them.

An even more drastic solution, not so daunting if done while undergoing a major refit, is to see what weights can be re-arranged to better balance the boat on its planing CLP (centre of longetudinal pressure). Things like tankage, batteries, spare anchors & rode, gensets, etc., if moved forward may assist in getting rid of the squat.

In all planing craft, the evil monster is weight. Get rid of or reduce everything that adds weight to your boat. Be brutal. Shave. Clean your toenails. Anything to reduce weight. :D

[oldriverat]

What mmd said. I'd go with the trim tabs. The wedges are permanent. You may find you don't need or want them.

[Gary E]

Well.. now that you know what they are, how to make and install them, and I have outlined my preferences, you can get on with it.
.
.
.
OR... as you say here...
"Family and friends are putting on the pressure to see the boat in the water - get me ? "

OK dat settles it,,, fugitabout dem tings, wedgies, tabs whatever's...

GET THE BOAT IN THE WATER... NOW !!

smile.gif

[Allen Foote]

And have a happy boating season!! :D

[leon bee]

In practical terms, what would be the best way to cut a thin wedge 30 inches long? Band saw?

[Gary E]

Yes, a band saw with a fixture to hold the board on an angle, and that mounted on a base which rides up aginst the band saw fence.

If you draw the diagonal line on the board you want to cut, and build a fixture to fill in the space between the board and the band saw fence, you will see what I mean.

G

[Allen Foote]

Go to a lumber yard and see what they have for cedar shakes.