Whale tails and such for small outboards

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Antares

Veteran Member
Joined
Dec 22, 2015
Messages
59
Location
US
Vessel Name
Antares
Vessel Make
Canoe Cove 42 Sedan
I'm hoping to get the benefit of the collective experience of the group on the benefit of using a whale tail on the cavitation plate of my tenders outboard. The problem I'm trying to cure is an extreme bow up condition when accelerating to a plane. The dinghy is a WM hypalon 3.10 rib with a 9.9 Mercury 4 stroke. The motor is set at the lowest position (bow down) possible. Even with that keeping the bow from pointing at the noon sun requires my arm on the tiller stretched out straight and my ample center gravity as forward as I can reach. Once on plane and the bow comes down things are ok. With two people the boats behavior is more civilized.

Would one of the whale tail devices help in this situation and if so, which of the several brands have you experienced satisfactory results?
 
have the same dingy with an 8hp.

same issues.

put a Doefin on and it helps a little, but ultimately, moving weight around such as my 220lbs works best with a tiller extension.

once on plane and going faster the Doelfin helps more and I can move around a bit and stay on plane.
 
+1 to what PSneeld said. You might try moving your gas tank from the back end of th dinghy to up forward. It gets in the way up there but it sure helps getting on plane.


I've use whale tails on all of my outboards for the past 30+ years and swear by them. They may not get you on plane faster but they do help the porpoising when you're running on plane at slower speeds.
 
Similar experience with an Avon 3.1m and 9.9 4-stroke Yamaha. The Doelfin made a notable difference. It came with the motor when I bought it; tried it without at first since I’d never used one before, and boat was a little sluggish to plane. Put it on to try it, and never looked back.
 
When I bought a Caribe 10 new, with a Yam 20, it wanted to stand on the transom, or worse.
I put a Whale Tail on and it still wanted to rise to a 45° angle.
A pair of "smart tabs" did the trick. From then on it would rise onto a plane without pointing the front more than 1° or 2° up.

My next dinghy, a Caribe 12 with a 40 Honda, has a whale Tail and needs no more than that.
 
have the same dingy with an 8hp.

same issues.

put a Doefin on and it helps a little, but ultimately, moving weight around such as my 220lbs works best with a tiller extension.

once on plane and going faster the Doelfin helps more and I can move around a bit and stay on plane.

West Marine has a tiller extension with the ability to twist the throttle. I have one, I am happy with it. Price? I forgot.
 
Tiller extension is the answer. Do it cheap. Use thick wall PVC from Home Depot. Cut to desired length. With a hacksaw cut down the center long ways with the pipe on end to give the pipe some expansion. Use a high quality hose clamp. End cap if you want to get fancy.
 
I bought my RIB from a company that specializes in inflatable boats. They said that the overwhelming response from their customers was that almost all RIBs need these devices. They also said that their customers preferred the "single-tail" style with a single curved plate much more than the two-piece fins.

I just got an 8 hp outboard for my 10-foot boat and will try it first without one, then with an aluminum plate that I'll make myself. If neither configuration is satisfactory I'd look strongly at Smart Tabs.
 
3rd or 4th vote for a tiller extension. I've got 2 whale tails in the drawer. They do cause a boot of drag so you lose a knot or so of speed. You can keep this speed if you can get the weight to the bow. It's one less"thing" and you won't void any chance of a warrantee by drilling holes in your engine!
 
I could never get my 10’ RIB to plane with a 8hp 4-stroke. Granted my RIB is pretty heavy.
 
With a heavy boat (30 ft) and twin 300 outboards, the whale tails made a big difference. Just repowered and was hesitant to drill 4 holes in brand new lower units. But after 20 hours the whale tails are going back on. They will cost a MPH or two at the top end, but the stern lift is a must. Plus staying on plane at lower rpms for trolling. And, I can tilt the motor at the sandbar and have a great lazy chair!
 
Extendable tiller extensions are $20 and better than pvc pipe

s-l400.jpg

https://m.ebay.com.au/itm/76cm-Till...762068?hash=item1a478fe414:g:PlkAAOSwoRBagkz~

As for foils, i have tried several and aluminum ones are the best imho
Permatrim style are simple to make from 3mm plate with a jigsaw and a vice to bend.
 
Doel fin on my Achilles R.I.B. Will plane two heavy adults with an 8 h-P Honda. Without, not so much.
 
No experience yet but I once bought a fin for my 6 hp Mercury. However it did not fit on the 6 hp Merc. Used a tiller extension instead on my Zodiac 3.20 m. Worked fine. Now I have an Arimar 3.20 with a 20 HP Mercury. (Bought it from an Italian who said that it was fun) I used it just two times as all kind of things were broken. When I had everything fixed it appeared that the dinghy was overpowered. 15 HP is the maximum according to the book. As we use the dinghy only for short trips to the shore, looked for something else. At the end of the day I decided that it is much cheaper to put on the wail tail instead of changing boat and engine and when it doesnot do what's promised, I go for the smart tabs. Loosing a few mph will not bother me. Power enough.
 
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I bought my RIB from a company that specializes in inflatable boats. They said that the overwhelming response from their customers was that almost all RIBs need these devices. They also said that their customers preferred the "single-tail" style with a single curved plate much more than the two-piece fins.

I just got an 8 hp outboard for my 10-foot boat and will try it first without one, then with an aluminum plate that I'll make myself. If neither configuration is satisfactory I'd look strongly at Smart Tabs.
Almost all RIBs need these devices? That's precisely why I got rid of my 11-foot Zodiac. My wife HATED the nose-up tendency of the Z. It frightened her. At less than planing speed the Z would wallow and wander. And she did not like going fast. Replaced it with an 11-foot Boston Whaler clone, a Bluewater Baby. We absolutely love it. Now, as for the Whale Tail, the Yamaha 25 on the Zodiac had one. It worked well.
 
This is such a common problem I don’t understand why boat designers don’t address it. What is needed is some planing surface further aft. I built a 14 foot plywood Skiff and put a 15 on it. The bow would climb for the sky with just me in it. I hate tiller extensions and putting fins on the lower unit just strikes me as wrong. Too much drag.

I solved the problem with a set of small fixed trim tabs. They are set parallel with the bottom of the boat. When the bow rises, the tabs dig in adding lift at the stern, the bow never rises much and the tabs add no noticeable drag when the boat is on plane.

Every inflatable designed to plane has tubes that extend aft past the transom. If the designers could figure out how to make them flat on the bottom, I bet that would solve the problem.

(Photo is before tabs were installed, use your imagination)
 

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The smart tabs work very well. Need to get the correct size and force. My 11.5 Achilles with a 30 hp jumps right on plane solo. The tabs also help the dinghy plane at lower speeds. The only downside is they need repair every couple years but I will always use trim tabs if possible
 
The tender on Sonas came with them. I am not sure of the value since it is an 11 RIB with a 25hp four stroke Yamaha, which I feel would not have an issue with getting on plane anyway.

However, after a couple of years of use I have found one disadvantage and one advantage.

The disadvantage is that when you are coming off the back of a wave or, more usually, a wake, the fin can make you broach because one side is digging in while the other is catching air. This is even when throttling back and taking it easy.

The positive I found out when I struggled to get back onto the RIB from the water. You can use the fin as a step plate so long as you are careful to put as much of your weight on the engine or transom/tube as you can, so as not to snap it off. I have recovered wife and guests that way where I have their arm.
 
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I have been having a very hard time locating a fin for my 25hp Yamaha. Any suggestions on where to find one?
 
The smart tabs work very well. Need to get the correct size and force. My 11.5 Achilles with a 30 hp jumps right on plane solo. The tabs also help the dinghy plane at lower speeds. The only downside is they need repair every couple years but I will always use trim tabs if possible
What happens to them that you have to repair them every couple of years?
 
I have been having a very hard time locating a fin for my 25hp Yamaha. Any suggestions on where to find one?

I just looked. The brand name on mine is Hydro-Stabilizer.
 
What happens to them that you have to repair them every couple of years?

twice in five years I have had to replace a pressurized cylinder that provides the trim tab force. These are like hatch cylinders but enclosed in a "water proof" rubber housing. And just last week I noticed my 5 year old smart tabs have a trim tab that the hinge is starting to fail. But, they work so well for a reasonable price on my dinghy, that I am still happy:)
 
twice in five years I have had to replace a pressurized cylinder that provides the trim tab force. These are like hatch cylinders but enclosed in a "water proof" rubber housing. And just last week I noticed my 5 year old smart tabs have a trim tab that the hinge is starting to fail. But, they work so well for a reasonable price on my dinghy, that I am still happy:)
Thanks for your explanation.
I think that the force on the smart tabs and the cilinders is pretty big. But I think that this will even more apply for the fins. Per square inch of fin the force must be enormous if you take into account that it has to lift up stern and engine.

A lot of opponents to fins say that they don't like drilling into the cavitation plate (but that issue can be avoided with fins that use other systems of fixing) but they also say that a fin can damage the stern, due to the upward force to the fixing bolts of the engine. But I have never heard that using the fin actually has damaged the boat or was the cause of an accident.

The smart tabs and cilinders are constantly working and correcting, where as the fin only has to work until the boat is plaining. But I am not an expert. And after all: boats cost money :blush:
 
I went with the smart tabs 2 years ago. I have a 9.5' aluminum rib with a 9.9 outboard. I have the 20# actuators and the set up works well. The only downside I can think of is that when beaching the dinghy, we have to lift the stern up off the sand to drag it back into the water or spin it around and pull it forward (like if the tide goes out and leaves the dink 30' up the beach) I suppose that if it bothered me enough I could attach a light chain to the tab that I could lift them and hook to an attachment point on the transom.
I have a friend that has a 12' rib that had no problem getting up and out of the water but porpoised a lot when running. No adjustment of trim would help. He put a set of smart tabs on it and they cured it.
 
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I have been having a very hard time locating a fin for my 25hp Yamaha. Any suggestions on where to find one?

Doel-Fin will make a huge difference. I have one on my 15 HP Yamaha, made a dramatic difference in how it planes and general stability. Took all the squirreliness out of the dink and it pops on plane. Highly recommend, not hard to install. Wouldn't be without them.

I've had experience with the mini-trim tabs on a friends boat, I was asked a number of times to repair them, seems they never lasted even a season, and when they didn't work (which was most of the time) the dinghy was a slug.
 
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