Whale tail on skegs

[Eagle]

Hi Guys, my mate has a 135 Opti on a Haines Signature 5.45 FB. The skeg has a wide whale tail bolted on to it that I am certain is making the boat very dangerous to operate. The boat is very hard to keep in a straight line, it keeps wanting to turn either left or right. When a turn is commenced, the hull leans into the turn but when straightened up it needs an opposite turn to force it back level. I think the previous owner bolted the whale tail on in an effort to raise the stern as the big Opti seems to be too heavy for the boat. The boat is not as wide in the beam as my own boat and does seem to be stern heavy.
I read some years ago that fitting a whale tail on a motor can be very dangerous as some reports stated that boats have rolled over as the leading edge of the whale tail dug into water. The effect is similar to the elevators/ailerons on the wing of an aircraft.
The whale tail is coming off this week and the boat will be trialled again in smooth water. What are your opinions of fitting a whale tail to the skeg? Have you had any problems or near disasters from using one?

[GBC]

We had a 542 cc with a 135 opti. They are a spot on match for power and weight. Once up on the planing plank the tail will be trying to lift the motor further, driving the bow in and causing it to drive left and right - yes you are basically trying to power into a flat water broach which is dangerous. Turning the opposite way to stand it back up you'll find that one side of the fin is still underwater - again most unpreferred. That svdh hull is great to drive and extremely trim sensitive which is also excellent if you can steer a bit and throttle a bit and can see how a boat sits/should sit.
The back of a signature sits pretty low at rest because of the deep V. The opti should throw it onto the plane with a decent handful of throttle then back it off (or not). Those fins can be dangerous, especially if it is going to dig while trimmed out in a following sea or coming through a bar and the hull gets out of level. Short of a tinny buzzing around with a fat bastard in it (me) I think they have no place on a boat.
Ours had a fin on it when we bought it. It lasted one trip and went in the bin.

[Moonlighter]

We had a 542 cc with a 135 opti. They are a spot on match for power and weight. Once up on the planing plank the tail will be trying to lift the motor further, driving the bow in and causing it to drive left and right - yes you are basically trying to power into a flat water broach which is dangerous. Turning the opposite way to stand it back up you'll find that one side of the fin is still underwater - again most unpreferred. That svdh hull is great to drive and extremely trim sensitive which is also excellent if you can steer a bit and throttle a bit and can see how a boat sits/should sit.
The back of a signature sits pretty low at rest because of the deep V. The opti should throw it onto the plane with a decent handful of throttle then back it off (or not). Those fins can be dangerous, especially if it is going to dig while trimmed out in a following sea or coming through a bar and the hull gets out of level. Short of a tinny buzzing around with a fat bastard in it (me) I think they have no place on a boat.
Ours had a fin on it when we bought it. It lasted one trip and went in the bin.

I agree.

The other thing is to check the engine height on the transom.

If the foil is underwater at cruise speed, the engine is likely to be set too deep. The cav plate (that the foil is attached to) should be skimming the surface, not under.

Sometimes people add foils to try to address symptoms rather than causes. Engines set too deep can make a great boat perform badly.

[bden]

Hi Guys, my mate has a 135 Opti on a Haines Signature 5.45 FB. The skeg has a wide whale tail bolted on to it that I am certain is making the boat very dangerous to operate. The boat is very hard to keep in a straight line, it keeps wanting to turn either left or right. When a turn is commenced, the hull leans into the turn but when straightened up it needs an opposite turn to force it back level. I think the previous owner bolted the whale tail on in an effort to raise the stern as the big Opti seems to be too heavy for the boat. The boat is not as wide in the beam as my own boat and does seem to be stern heavy.
I read some years ago that fitting a whale tail on a motor can be very dangerous as some reports stated that boats have rolled over as the leading edge of the whale tail dug into water. The effect is similar to the elevators/ailerons on the wing of an aircraft.
The whale tail is coming off this week and the boat will be trialled again in smooth water. What are your opinions of fitting a whale tail to the skeg? Have you had any problems or near disasters from using one?
when you mention a whale tail I assume you are talking about a foil? If so the se300 is a great choice for this combo. I put one on a 550c with a 135 opti and it works great. See how you go minus the fin but not all foils perform the same. Brett


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[Chris Tucker]

Your description sounds like what pretty much any boat will do if the engine is trimmed to far under. A foil will magnify this problem. So yes taking it of might "fix" the problem but so will trimming the engine further out.

[Marchy001]

Sounds to me like it’s running too deep. Foil should not be in the water at speed so if it’s better with the foil removed I’d jack that Opti up a hole at a time until prop blows out or water pressure drops. Then go down a hole and re test with foil.

[GBC]

The planing plank on a 542 is barely wider than the cav plate. The wings of the foil will be always wet from the v hence the handling traits , esp the flip flop out of a turn, no matter what the trim angle. They are a bad idea on that hull. I can’t vouch for the OP’s engine trimming skills or the height setup of his opti (most were done in the factory), but I can for mine.

[Noelm]

Pretty simple job to go to the ramp, test, pull boat out, or go to sandy beach area, remove foil, retest and note difference, while testing, look over the back at the cav plate when running, the whole exercise should only take half an hour.

[mal555]

Your description sounds like what pretty much any boat will do if the engine is trimmed to far under. A foil will magnify this problem. So yes taking it of might "fix" the problem but so will trimming the engine further out.

Agree totally