Trim Tabs Angle
 

Does amyone know why the trim tabs are mounted on an angle, usually the same angle as the hull ? When running on the water the boat is level, not on an angle like the hull. It would seem that if they were 90* to the water when running that they would hold the bow down better. When they are in the down position they are also angled out, which would put a drag on the boat when moving. Has anyone ever tried mounting them at 90* ?

Re: Trim Tabs Angle
 

Many performance boats mount their tabs flat or flater than the vee of the hull. Some of Fountains top boats are dead flat all the way at the edge.

Re: Trim Tabs Angle
 

Well then I guess I'm not to far off in my thinking....I was thinking about repositioning them.....I'll wait and see if anyone else has any opinions....

Re: Trim Tabs Angle
 

I just found a number of pics on fountains with the tabs mounted straight, or 90 degrees to the water, not on an angle matching the hull...hmm...I think I'm on the right track here with my opinion....

Re: Trim Tabs Angle
 

Some velocitys also mounted the tabs flat with the deck. If you were to look back at the bottom of the boat at speed the water comes off the bottom at the angle of the bottom. It would only be flat if the bottom were flat

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If thats the case, look at the bottom pic, the hull isn't flat, and the tabs don't match the angle of the hull.....

Re: Trim Tabs Angle
 

it doesn't make sense, though, if you have it mounted flat, perfectly in line w/ the hull what happens when your running the boat w/ the bow high? dont't the tabs drag in the water and slow the boat down? mine are set up that way and i am considering raising them

Re: Trim Tabs Angle
 

Jim I agree, the bottom is flat only in the area of the chines. I believe on a pad bottom like a velocity, the pad lifts the boat so high at speed that the v section on both sides of the pad have little contact with the water. Maybe that explains the flat mounting. I have seen both mounting positions on race boats. The most common by far is the tab at the angle with the bottom.

Re: Trim Tabs Angle
 

mcrsr You sure don't want the tabs to drag at speed. It is common to mount tabs 3/4'' above the bottom so they will not drag. There should be enough UP angle so the tabs do not touch when the boat is trimed out. Remember the best running angle on a well set up hull is only 2-4 degrees

Re: Trim Tabs Angle
 

From what I could find, it seems all the newer fountains have the tabs 90* to the water, the older ones are on an angle equal to the v hull. They must of changed it for good reason...it wouldn't be a very big deal to reposition mine, maybe I need to make the change and then see what difference it really makes....

Re: Trim Tabs Angle
 

one method puts more tab in the water than the other, all depends on what your hull needs...

Re: Trim Tabs Angle
 

I have hydro props that lift the stern well, but on lake michigan well the swells are deep the front end seems to want to bounce up and down to much. When I put the tabs all the way down it does help alot...it seems if I had a bit more tab down force that the boat would be more stable in the rough. My tabs are long enough, I just think they would work better if the downforce was in line with the surface of the water.

Re: Trim Tabs Angle
 

Jim Be sure and post your results. There is nothing like real world testing to answer questions

Re: Trim Tabs Angle
 

My understanding is that mounting the tabs flat was a solution to a chinewalking problem. As far as lifting performance goes, I think it is a wash either way. With the tabs parallel to the running surface, the tab is in the optimal contact to the water to make lift, but that lift vector is not directed straight up. With the tabs set level, they are not meeting the flow straight on, and will actually funnel water back toward the boat centerline, and that momentum reaction will cause an outward force in addition to an upward force. The relative quantaties of all of these can be computed on a by-boat basis, but in the end, realize that the tabs are only needed for transom lift through getting on plane and maintaining longitudinal/vertical stability from porpoising through the midrange. If you need anything in the top end, it's only going to be the tip of the tab anyway, and it's efficiency as a pure lifting surface is not nearly as big of a concern as how much lift the incredibly small angles of attack can produce at high speeds, and how the boat will react to it.

Re: Trim Tabs Angle
 

What about the effect on turning if you were to mount them flat ???? Too much drag on the boat I would think.

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Skater, take a look at the pics above...did you ever see a fountain have a turning issue? I would think that theres less drag in a turn...just my 0.02

Re: Trim Tabs Angle
 

I checked the flow of the water on mine with the tabs angled. Right now the water flow is being funneled back toward the centerline. It almost appears like it actually causing alot of turbulance toward the props. I still would like to know why on the 2005 fountains they are mounted straight accross the stern.

Re: Trim Tabs Angle
 

I posted a thread in the fountain owners area, here was a responce..

According to Fountain, "to get more leverage while reducing wetted surface drag". I guess they have been doing it on the racing boats and it makes a big difference in tab effectiveness.

It is good to see that racing technology works itself down to the production level.

Sounds like I'm on the right track with my thinking....

Re: Trim Tabs Angle
 

ok the tabs came off last night, tonight they go back on straight. Thursday night will get the test, I'll post the results...

Re: Trim Tabs Angle
 

Try drilling some holes in one of the tabs like you did on the Chris Craft.

Re: Trim Tabs Angle
 

Mine are mounted flat, but like someone else mentioned Velocity has been doing is for more than 10 years. I am running the long 380s. Not 100% sure why but I did ask a few people that deal closely with Fountain. If the tab is at an angle which way is it pushing the boat, straight up or to the side? If they are mounted flat then they will push that side of the boat straight up.

Re: Trim Tabs Angle
 

OK, I give up, what are you talking about now ? What part of "I bought the boat used" don't you understand ? The used, or I bought it used ? Lets see...when you sell the boat to the next buyer should he blame you for everything that goes wrong with it over the next 2 years ? Like I said once before...you came and checked it out, if it was so bad then why did you buy it ? Maybe you should have brought your crystal ball along with you that day. In other posts you mentioned that you don't get payed much...funny how its always the ones without money that piss and moan everytime something goes wrong with their car,boat,bike...your in way over your head, stick to just watching tv for your entertainment and you will be a happier person..lets just hope the tv never stops working !!!

Re: Trim Tabs Angle
 

Nope. But then I am not a con man either.
I hooked the hour meters back up after I got it from you.

The manifold gaskets, couplers, shift cables, trim solenoids, trim rams, bad fuel sending unit with no access because you floored over it, ESA modules, distributors, and leaking Y-pipes have also been taken care of.

It's ok. You got your karma right away when you bought your 29 from Tim. After all, are you gonna blame Tim for selling you a used boat?

I just thought that you must have drilled those three holes in the one trim tab for some kind of polish engineering purpose.
What did you do, try to bolt on a trim tab extension or something?

Re: Trim Tabs Angle
 

The hour meters never worked when I bought the boat, and why would I worry about hooking them up ? The boat is how old ? a 1987? like it would really matter or be the correct hours ! are you that dumb ? oh, and could you please check that crystal ball of yours and let me know when I will have to replace these things you mentioned..."The manifold gaskets, couplers, shift cables, trim solenoids, trim rams, bad fuel sending unit with no access because you floored over it, ESA modules, distributors, and leaking Y-pipes have also been taken care of." Thanks, I appreciate knowing when those parts will fail on mine. Oh, by the way, are you offering any warranty with the sale of yours?

Re: Trim Tabs Angle
 

Maybe because you advertised the boat as having 400 hours on it? Advertising the hours on a boat kind of implies that they are accurate. (Well, at least to honest people.)

I won't offer a warranty on the boat when I sell it, however, I won't lie to the guy either. And I will sell it in seaworthy condition.
Of course, I am not a con man like you.

It's ok though.
You already got what you had coming to you when you bought your 29.

I got "Jimmed."
You got "Timmed."

I am pretty sure that you got the worst of it from reading the post where you said that he should refund your money on the boat and he said that you are from another planet.

That was classic. :D

Re: Trim Tabs Angle
 

1. remember, your hull isn't a fountain.... (steps and all that..)

2. with the tabs parallel (90* tabs would be kind of a new concept..) to the water, given the same amount of cylinder stroke, you are going to put more tab in the water, that could be a good or bad thing.... once again, depends on the hull....

3. if the tabs are wet, they are dragging.. doesn't matter if they are set at a horizontal or an angle.....

4. if you set the tabs flush with the hull ( i read that in one your posts farther down), when you want to pull them up, you may still be dragging them, thus slowing you down... you will notice most boats space the tab up from the bottom of the hull slightly, even the fountain's parallel setup is spaced on the outside corner slightly so they don't drag at top speed...

5. i would imagine your trim switches will be more sensitive (due to more tab getting into the water faster....)

6. the water coming off the bottom of your hull is not the same as flat water, it does have some "vee" in it... the deeper the vee of the boat, the more pronounced the effect

Re: Trim Tabs Angle
 

Sean, I am planning on mounting them in about 2" more than the ones on the fountains. And due to the length of the hydraulic hose for the rams, they will end up being on about a 80 to 85 degree angle, not the 90* that the fountains have. The pics I have of me running wide open show the back of my boat out of the water pretty good ( have hydro props on it) so my thinking on mounting height show not cause any problems. I'm actually looking to get more tab action for cruising speed in the deep swells out here on lake michigan. I'm not looking to put the nose into the water..but just to help hold it down from being lifted by the swell. With twin engine weight in the rear, it seems to make it alot easier for the front end to want to come up. I figure it will either improve, or worse case I put them back where to were. I plan to just put the screws back in the existing mount holes with some sealant, so I will be able to reuse the holes.

Re: Trim Tabs Angle
 

Testing is done, I picked up 3 mph wot with the tabs down, and the bow doesn't come down as hard in the rough, so they will be staying mounted on straight.

Re: Trim Tabs Angle
 

Jim are you saying your top speed has picked up with the use of tabs? Sounds like that is a great gain

Re: Trim Tabs Angle
 

so your boat is faster with the tabs down versus up, or you gained 3 MPH tabs down (new style) versus tabs down (old style)....

Re: Trim Tabs Angle
 

[QUOTE=fund razor]
I just thought that you must have drilled those three holes in the one trim tab for some kind of polish engineering purpose.

Hey, why did you have to go and bring me into this ? Polish is spelled with a capital " P" mister. :D
By the way, any fool would know those holes are for hooking up a second ski rope. :drink:

Re: Trim Tabs Angle
 

[QUOTE=rich allen]I believe the original poster wouldn't understand your answer...but I enjoyed it ! lol

Re: Trim Tabs Angle
 

you guessed it correct, with the tabs mounted on an angle and put down in the rough as needed the boat lost 3 mph. with the same rough condition and the tabs straight and down it gained back the 3 mph. I could also feel and hear a difference when putting the tabs down the old way, much more drag on the boat and the engines....just makes sense that there would be less drag having them straight....

Re: Trim Tabs Angle
 

[QUOTE=rich allen]Oops. My fault. I should have been more specific. I meant POLLOCK.

Here: I thought that Jimski must have drilled da three holes in da one tab for some kind of POLLOCK engineering purpose.
Since our friend Jimski is a relentless re-engineer of trim tabs, maybe da holes were to attach some kind of panel over da tab to increase da size. After all, it is clear that he doesn't mind drilling holes in anything. He hadn't gotten da idea to change da location yet. He was probably trying to make dem bigger.

Of course, this is the same guy who installed a velcro strip on the steering column so that he could leave the helm and go down below to have a smoke with Tammy during those long boring Lake Michigan rides. (true... not a joke.)

Velcro steering wheel= Polish Autopilot. :D

Re: Trim Tabs Angle
 

FUND RAZOR.....I can't count the number of times you said you didn't make much money, and don't have any money...
To bad your not the POLLOCK you refer me to be....50k boat paid for, 30k 2500 diesel ram paid for, 250k house(owe 11,000.00)
15k 2002 durango paid, 8k 97 ram1500 paid, 1999 durango 5k paid.....ya Fund....sure is tough being a POLLOCK ! lol
Please continue to post your ignorant replys, Tam and I look forward to them....

Re: Trim Tabs Angle
 

If Tam read your posts you wouldn't be hitting on the female members like you do.

I have no problem admitting that I am among the lowest paid members of OSO. In fact, I'm not ashamed in the least. I also have one of the most honest and decent careers that you can get. I have turned down high paying jobs that would require me to hide things from people while I sell them something. Kind of like you.
But I prefer to make less and contribute more. It feels good to know the children that I provide for and to see my efforts result in a better quality of life for kids who are facing things that we adults shudder from.

So... since I made you so defensive and insecure that you had to post a public laundry list of what you have and what you think it is worth...
I'll let this thread go back to you drilling a bunch of holes in your boat and teaching Baja how to rig.

I'll post a fresh thread featuring the special engineering touches that you did to my boat later.

Say Hi to Tam.

Re: Trim Tabs Angle
 

lol, lol, you crack me up ! please continue with your posts, its one of the reasons I renewed !

Re: Trim Tabs Angle
 

You really cracked me up with the term

"Ignorant replys." :D

(If you don't get it it's ok. We are all God's children.)

Re: Trim Tabs Angle
 

On the track of trim tabs--mine are mounted in line with the V bottom/not parallel to hte water. I've learned that with the tabs down the boat runs flatter so I can drive sitting down with the forward hatches open and most importantly at WOT I throw some sweet rooster tails.

A serious technical question--If I upgrade from the 280 to the 380 tabs will the rooster tails be better (larger) and will the boat run flatter with less tab angle?

Re: Trim Tabs Angle
 

hey Jim, sea ya next spring I guess...gonna be a long winter.