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Old 03-22-2018, 07:07 PM   #1
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Whale tails and such for small outboards

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?
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Old 03-22-2018, 07:25 PM   #2
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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.
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Old 03-22-2018, 07:46 PM   #3
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+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.
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Old 03-22-2018, 08:24 PM   #4
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Yes it will help.
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Old 03-22-2018, 08:29 PM   #5
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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 Iíd never used one before, and boat was a little sluggish to plane. Put it on to try it, and never looked back.
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Old 03-22-2018, 08:52 PM   #6
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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 45į angle.
A pair of "smart tabs" did the trick. From then on it would rise onto a plane without pointing the front more than 1į or 2į up.

My next dinghy, a Caribe 12 with a 40 Honda, has a whale Tail and needs no more than that.
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Old 03-22-2018, 09:09 PM   #7
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Quote:
Originally Posted by psneeld View Post
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.
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Old 03-22-2018, 09:22 PM   #8
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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.
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Old 03-22-2018, 09:38 PM   #9
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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.
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Old 03-22-2018, 09:57 PM   #10
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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!
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Old 03-22-2018, 09:59 PM   #11
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I could never get my 10í RIB to plane with a 8hp 4-stroke. Granted my RIB is pretty heavy.
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Old 03-22-2018, 10:07 PM   #12
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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!
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Old 03-22-2018, 10:13 PM   #13
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Extendable tiller extensions are $20 and better than pvc pipe


https://m.ebay.com.au/itm/76cm-Tille...kAAOSwoRBagkz~

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.
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Old 03-22-2018, 10:55 PM   #14
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Doel fin on my Achilles R.I.B. Will plane two heavy adults with an 8 h-P Honda. Without, not so much.
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Old 03-22-2018, 11:11 PM   #15
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Originally Posted by Simi 60 View Post
Extendable tiller extensions are $20 and better than pvc pipe


https://m.ebay.com.au/itm/76cm-Tille...kAAOSwoRBagkz~
.....
I stand outside the cabin reversing into our berth,reach in and play with the gear levers without looking. But with a tiller extension,which I think are great things,rotating the right way to increase/reduce speed, arm outstretched sitting facing fwd, does not come easy.
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Old 03-23-2018, 04:07 AM   #16
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Smile

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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Old 03-23-2018, 05:11 AM   #17
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Quote:
Originally Posted by Sabre602 View Post
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.
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Old 03-23-2018, 08:50 AM   #18
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This is such a common problem I donít understand why boat designers donít 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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Old 03-23-2018, 08:59 AM   #19
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Actually at least one boat designer did address the problem.
Take a look at this boat sold by Plastimo.
https://www.plastimo.com/en/mooring-...n-ii-8796.html
Note the flaps that extend aft of the transom. Scroll down to the description of the flaps.
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Old 03-23-2018, 09:32 AM   #20
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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
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