Tub Distance from Water

[Mike Rappold]

For a 90 size boat, what is the general distance from the water's surface to the bottom of the tub?

Thanks in advance.

Mike

 

[Marty Davis]

An inch is a real good compromise for that size boat.

Marty Davis

 

[John Finch]

Marty,

We were just talking about tub height on the twin flat bottom thread. You had a lot of input on some very fast boats over the years and some R&D on some of the top performers still in production today. What is your feeling on a tub close to the water at say an inch off the water opposed to a tub 1.5 inches off the water. Will the tub closest to the water pack more air pressure ( ground effects) that the hull further off the water causing the boat to leave the water sooner than the tub at 1.5 inches if it packs a lot of air under the hull? I know tub widths, scale hull vs rigger etc. make a difference but for lets say a rigger for example. Also, would the higher tub make cornering more difficult. What is you opinion?

 

[Marty Davis]

John:

I think that the reason that I like the 1" on the large boats and 3/4" on the 20's and 40's is that it gives some clearance for rough water. Not sure about packing air. I doubt that a little difference here makes a big difference in air packing. The slope up on the rear of the tub does have a big impact on keeping the rear of the boat down on the water. As for flying, it think it is more of a balance thing (CG) and front sponson width. I know that Ralph made the big twins further off the water and it really helped. I think it was more of a clearance thing (waves) than anything for his improvement. I have run 67 boats at 5/8" and they were terrible in rough water.

I spend a lot of time with my turn fins and I think that CG (front to rear) is probably more important than higher cg in the turning area.

Marty

 

[Tony Jacuzzi]

Marty is there a ballpark formula or percentage that you use for CG on riggers?

 

[John Finch]

Thanks Marty.

John

 

[DON MAHER]

Marty ,

Could you expand on the slope up on the rear of the tub keeping the rear of the boat down. Great topic!

Don

 

[Marty Davis]

Thanks Marty.

John

WOW, that is the shortest response that I have ever seen from you.

Marty

Marty ,

Could you expand on the slope up on the rear of the tub keeping the rear of the boat down. Great topic!

Don

Don:

Really simple, it creates a low pressure area that keeps the rear of the boat down on the water. The Indy Cars use this throughout the bottom of their cars to suck the car down. It just works in a specific area with out boats. I have always wondered why the outboard guys didn't use this to keep their tunnels on the water.

 

[Marty Davis]

Marty is there a ballpark formula or percentage that you use for CG on riggers?

Tony:

Too many variables to have any type of ballpark. You would have to specify a lot of things in order to be able to answer your question. It is really a package. You can see the main boats and how they vary in all aspects. The Eagle and the JAE have a rearward weight and the Crapshooter and the Roadrunner a more mid CG. Many things make all work well.

 

[John Finch]

Thanks Marty.

John

WOW, that is the shortest response that I have ever seen from you.

Marty

Marty ,

Could you expand on the slope up on the rear of the tub keeping the rear of the boat down. Great topic!

Don

Don:

Really simple, it creates a low pressure area that keeps the rear of the boat down on the water. The Indy Cars use this throughout the bottom of their cars to suck the car down. It just works in a specific area with out boats. I have always wondered why the outboard guys didn't use this to keep their tunnels on the water.

Yup!

 

[Andy Brown]

Marty is there a ballpark formula or percentage that you use for CG on riggers?

Tony:

Too many variables to have any type of ballpark. You would have to specify a lot of things in order to be able to answer your question. It is really a package. You can see the main boats and how they vary in all aspects. The Eagle and the JAE have a rearward weight and the Crapshooter and the Roadrunner a more mid CG. Many things make all work well.

Eagles are 50-50. I think JAE is 60-40.

 

[Terry Keeley]

Ooops, moved to other thread...