Lifting Rails, Engine Dolphin, Trim Tabs

JimRP31

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I own a SISU 22. When I first purchased it the lifting rails were too small and too high above the waterline. The boat did not plane well and keel walked in a following sea. Some of you may have seen my thread when I replaced the lifting rails last spring. The new rails make a big difference. The new rails all but eliminated the keel walking and helped get the bow down making visibility a lot better. The only problem was I still felt I needed to get the bow down more and the boat tend to porpoise through waves.

I have thought about trim tabs but the cost is substantial for a solution I was not sure would work. I bought a Stingray Stealth 2. It was only $60 so a inexpensive investment to see if it would help. I put it on the engine a few weeks ago. It got the bow down and help keep the boat from porposing while going through waves. The downside is that in side waves or following sea it amplified the keel walking to the point I had to take it off. The boat would snap back and forth, getting it back under control required a lot of steering and backing off the throttle. It think the foil lifted the stern enough that the lifting rails lost lift and when they dug in the foil prevented them from coming back up.

My question to the group is if I the foil caused the boat to keel walk more often then what are my other options. Will trim tabs work at all or cause the same problem? Any input is welcome.
 

steveinak

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get some UHMW plastic and try making a fin half the size of the one you have now it might just work or do the old rope under the transom trick, try it with some of that braided nylon cord that they used to use for swordfish longline or just try it with some 1/4" pot warp, loop it under the stern up and over the top of the transom and get it tight by twisting a stick or 2x2 around it till you get it good and tight. A nice piece of that orange poly twine (5MM) they use for trawls might even be enough??? look around the boatyards you might find a set of trim tabs on a junk boat ???
 

JimRP31

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Steve,

Thanks. The smaller fin might work in a following sea. But I think I would lose the benefits into the wave. I have thought about trying rope under the transom trick. Might be time. I was going to take some warp and loop it under then tighten it up with a trailer tie down ratchet. I was worried it could crack or bend the lifting rails. I keep trying solutions until I come up with something.
 

steveinak

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Steve,

Thanks. The smaller fin might work in a following sea. But I think I would lose the benefits into the wave. I have thought about trying rope under the transom trick. Might be time. I was going to take some warp and loop it under then tighten it up with a trailer tie down ratchet. I was worried it could crack or bend the lifting rails. I keep trying solutions until I come up with something.

put some blocks of wood under the rope so it holds the rope off the rails.
 

BOSBoatMan

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JKPORTER

We are both in the same boat (no pun intended). I've got a 17' Leblanc Bros center console with a 90 ETEC on her. My boat porpoises as well when lightly loaded (one person, full fuel ~ 40 gallons on bow) at anything greater than 21 knots esp if going into wind. With the wind and more weight on the bow I can hit almost 30 knots.

I am at a crossroads as well. I can't put a foil on the engine due to my warranty and likewise, people just don't put trim tabs on sub-twenty footer's...

So I suppose that the only thing left to do is add weight to the bow to keep her down....
 

MASTERENEGADE

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I use the rope trick everytime, Either 1/2" or 5/8 depending on how many and heavy the guys are on my charter for that trip.
When the water hits the rope it creates a wedge and gives the transom lift like a trim tab would in the down position. I've found this is great up to 14knts when i try to go faster it creates too much lift and forces the bow down too much. Which for charters in the sound is all i need. Im not going that far and also why burn the profits.

I do want to put a set of the flat tabs on the boat eventually on the next haul hopefully.
What i love about the rope is that its cheap and nothing ever breaks :)
 

BOSBoatMan

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So what do you do cleat it from the starboard stern cleat (under the boat) to the port stern cleat? WTF? Or am I totally missing something?
 

Old Mud

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MASTERENEGADE

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Bosboatman thats exactly what you do. I know its not the same as trim tabs. But with all the fishing lines and my anchor lines(my anchor is done from the cockpit) I just know i would loose fish and probably break one off.
 

MASTERENEGADE

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heres two shots of the boat running one with out the rope and the second int he darker picture if you look towards the transom you will see the rope running down the hull.

drifanclinton.jpg

SIDEDRIFAN 009.jpg
 

JimRP31

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We are both in the same boat (no pun intended). I've got a 17' Leblanc Bros center console with a 90 ETEC on her. My boat porpoises as well when lightly loaded (one person, full fuel ~ 40 gallons on bow) at anything greater than 21 knots esp if going into wind. With the wind and more weight on the bow I can hit almost 30 knots.

I am at a crossroads as well. I can't put a foil on the engine due to my warranty and likewise, people just don't put trim tabs on sub-twenty footer's...

So I suppose that the only thing left to do is add weight to the bow to keep her down....[/QUOTE]

Yes we are in the same boat. I think you can try a foil without breaking your warranty. The one I tries was no drill. It stayed on going 25 knots. Might be worth a try.

Since no one has recommended adding trim tabs I am going to save my money for the time being. Thanks for the input.
 

BOSBoatMan

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MASTERRENEGADE...

So what kind of size would you recommend on a 17x8 center console? Since you've got 30' and your using a 1/2 - 5/8....what should I use? 3/8 or is that not enough?

JKPORTER

Thinking trim tabs make a great Christmas present....what's the point of haulin' out now...? Best time of year's approaching!
 

MASTERENEGADE

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Bosboatman. I'd try 1/4" poly or 3/8. The only small problem with thin nylons is that when they get wet they will stretch a lil bit, so if you use nylon rope make sure you really snug up the lines as tight as possible on the cleats. Otherwise the rope will slip of the transom. Since tied to cleats it wont go into your prop.
 

MASTERENEGADE

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Anytime: try both sizes, and wait till you see the differance it makes. You may findout at higher speeds its even too much. But one way to find out. Have fun.
 

BOSBoatMan

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I gave this a shot on Saturday....agreed it does work good.

However I tried to open it up some and my RPMs shot up like a bastard. Is it safe to say that it worked too well that I ended up cavitating the son of a bitch?

Also I noticed that I started throwing a ferry wake
 

MASTERENEGADE

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If i had to guess, with your boat and the speeds your trying to reach, the rope maybe too much and tabs maybe the only way. If put the hammer down on the jc the rope is useless. It digs too much. But for my cruise speeds its perfect.

Atleast you got the see the effect of what the rope does.
 

BOSBoatMan

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So what's your cruise speed at with the JC with the line out on the stern like in the top picture? I realize we have completely boats but if I had an idea where the bow starts stuffing for you it could be helpful when I try it again...thanks.
 

Toolate

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If you already bought the fin why not take a jigsaw to it and make it 1/3 smaller and try again? Sounds like it worked but too much so maybe just take a little away and repeat until problems go away or get worse.
 
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