Mono Skipping In The Turns

[Dr Hydro]

I have a Youngblood mono with the COG set at 33%. I've tried the turn fin at 1 1/2 and 2 inches below the bottom. The right trim tab is set to just touch a straight edge laid on the bottom. The left is set 1/32 above the straight edge. The turn fin seems to lift the right side out of the boat out of the water and the prop unloads. Then it digs in again and does the same thing. The stinger is set level with the keel. This is the version with the delta pad. Any suggestions would be greatly appreciated.

 

[Terry Keeley]

Can you take a pic straight on from the back?

 

[Dr Hydro]

Here ya go. The turn fin is 90* to the bottom and extends down where the side meets he bottom (if that's what you are wondering).

 

[Terry Keeley]

What happens if you take the turn fin off?

 

[David Ashcroft]

,,Youngbloods typically not the best hull in turns,,,try glass the pad and form a small vee as a continuation of the keel ...

David

 

[moparbarn]

,,Youngbloods typically not the best hull in turns,,,try glass the pad and form a small vee as a continuation of the keel ...

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David

I agree, i've had both versions of the speedmaster mono. The first gen. with the sharper vee handdled better. The later one had a rounded keel had issues similar issues to what os happening to you. A longer rudder helped mine, but did not cure it. If you add a vee to yours, i would suggest using auto body filler. If you don't lile it, bondo is MUCH easier to remove later.

 

[anthony_marquart]

Turn fin looks a little short..

 

[tnrcboatracer]

The cause of the problem on the Youngblood is not at the transom or keel. I the a solution (confirmed) for you if you want it.

Jon

 

[tnrcboatracer]

The cause of the transom blow out is the chine at the bow. Add a piece of 1/8" bass wood stock to the outside of the right side chine from the bow to where the chines become parallel. The intent of the strip is to break the suction that pulls the bow down when the hull rolls over in the turn. It works by interupting the flow up the side of the hull. This has been confirmed on K&B 1.0 YB mono at the internats back in '98 or so. There was a thread about it on here several years ago. Try searching for 'bernoulli'. I have reposted the specific post in the thread a few times since then.

 

[tnrcboatracer]

I just saw yourprvious post where you added the strip to the chine. Please post a pic of the bottom with the strip that you added. 3/16" is a little big, but should work.

 

[tnrcboatracer]

In reviewing the pics in your first post, it appears that your strips go too far to the rear. The strips are only applied to the bow curve area of the chine. Search for 'bernoulli scooter' and llok on page 4, post #48.

 

[John Finch]

I don't doubt the suction problem in the turns. The boat is not a good oval hull. I do know that having the turn fin the same depth as the keel will cause the boat to rock left as the fin acts like a ski if at the right depth. Try making the fin deeper than the keel. Also a little sweep back as you go deeper on the leading edge will help stability. You dont want the turnfin to have a straight up and down profile like the rudder. Swept back is better. I saw the same problem at the lake two weeks ago and a deeper turn fin fixed the problem. Also make sure the fin is parallel to the keel. If it is slightly bent right or left it will cause the same issue.

John

 

[tnrcboatracer]

You are correct that the suction can be overcome with a larger turnfin. Even with the increased fin length, the rear can still blow out if the water surface conditions allow the fin to lose its anchor in the water. In my opinion it is better to reduce the suction at the front end of the hull and fine tune with a small turn fin. I think the smaller fin does not mak the hull as sensitve in the turn. I also always use a swept or radiused edge fin profile.

 

[Dr Hydro]

Never tried it without the fin.

 

[Dr Hydro]

The turn fin is swept back and I now have it about 3/4 inch below the keel. The wood I added to the chine is 1/8, not 3/16. If I fill in the pad with bondo my prop will be about 1/2 in above the keel so that is not an option. Thanks for he info guys.

 

[tnrcboatracer]

Let us know how it works. What is the height of the fin from tip to the hull bottom surface (perpendicular depth). The Mucks hulls are considered a medium V angle, and therein lies some of the problem. I'm curious as to your fin depth into the water when the hull rolls over onto the right side.

The wood strip in your picture seems to go from tip to stern. It should end about 40% back from the nose. Having the water roll up the rear end of the hull will help keep it planted in the turn. You really only want to break the suction at the front end.

 

[David Ashcroft]

Just looking at your tabs there seem to be too far from the keel

Considering they are small tabs..maybe bring the tabs into the keel more about 1 1/4" from the strut hole..and it may give more control to what the rear is doing in the turns...

David