Concavity

[T.S.Davis]

You guys have probably been over this before. Sorry for the ignorance.

What is the advantage/disadvantage toconcavity on mono hull?

 

[T.S.Davis]

Holy smokes. Nobody knows? haha It's referenced in the rule book for some reason.

 

[BigChuck]

Is it the same as " Hook in the Bottom?" B)

 

[dwilfong]

The reason no one talks about it is that by the NAMBA rule book many boats are not legal .

IE THE HOOK

I know this will stir the pot.

4. Concavity – When checked with a straight edge at right angles to the keel at any point

​

between the transom and the mid-point of the hull length, no depression, step or

​

concavity will exceed the dimensional limits for strakes.

​

5. Strakes - Regardless of the type or purpose, must conform to the following rules:

​

a. Strakes will be no more than 3/4" wide and 5/16" deep. For hulls over 46"

​

long and a beam width over 15", strakes will be no more than 3/4" wide and

​

1/2" deep.

 

 

David

 

PS I my self like to play on a level playing surface.

 

[Rokieboater]

The reason no one talks about it is that by the NAMBA rule book many boats are not legal .

IE THE HOOK

I know this will stir the pot.

4. Concavity – When checked with a straight edge at right angles to the keel at any point

​

between the transom and the mid-point of the hull length, no depression, step or

​

concavity will exceed the dimensional limits for strakes.

​

5. Strakes - Regardless of the type or purpose, must conform to the following rules:

​

a. Strakes will be no more than 3/4" wide and 5/16" deep. For hulls over 46"

​

long and a beam width over 15", strakes will be no more than 3/4" wide and

​

1/2" deep.

 

 

David

 

PS I my self like to play on a level playing surface.

The rule does not state that hooks are illegal is states that they will not exceed the (SAME) dimensional limits for strakes. Or in other words, have the same dimensional limits as strakes. For example the depth of the concavity cannot exceed 5/16 deep. The drawing in the rule book shows that.

But of course if you want to make it more than it is have a good time with that.

Robert

 

[dwilfong]

The reason no one talks about it is that by the NAMBA rule book many boats are not legal .

IE THE HOOK

I know this will stir the pot.

4. Concavity – When checked with a straight edge at right angles to the keel at any point

​

between the transom and the mid-point of the hull length, no depression, step or

​

concavity will exceed the dimensional limits for strakes.

​

5. Strakes - Regardless of the type or purpose, must conform to the following rules:

​

a. Strakes will be no more than 3/4" wide and 5/16" deep. For hulls over 46"

​

long and a beam width over 15", strakes will be no more than 3/4" wide and

​

1/2" deep.

 

 

David

 

PS I my self like to play on a level playing surface.

The rule does not state that hooks are illegal is states that they will not exceed the (SAME) dimensional limits for strakes. Or in other words, have the same dimensional limits as strakes. For example the depth of the concavity cannot exceed 5/16 deep. The drawing in the rule book shows that.

But of course if you want to make it more than it is have a good time with that.

Robert

And 3/4" wide

 

[Andy Greene]

Someone please pass the popcorn

I got some extra cold ones if you guys get thirsty too

Tom , Im thinking we need to add a "lazy boy" avatar-

Pulling the handle and kicking back / tossing popcorn in his mouth- B) B) B) B) B)

 

[Rokieboater]

The reason no one talks about it is that by the NAMBA rule book many boats are not legal .

IE THE HOOK

I know this will stir the pot.

4. Concavity – When checked with a straight edge at right angles to the keel at any point

​

between the transom and the mid-point of the hull length, no depression, step or

​

concavity will exceed the dimensional limits for strakes.

​

5. Strakes - Regardless of the type or purpose, must conform to the following rules:

​

a. Strakes will be no more than 3/4" wide and 5/16" deep. For hulls over 46"

​

long and a beam width over 15", strakes will be no more than 3/4" wide and

​

1/2" deep.

 

 

David

 

PS I my self like to play on a level playing surface.

The rule does not state that hooks are illegal is states that they will not exceed the (SAME) dimensional limits for strakes. Or in other words, have the same dimensional limits as strakes. For example the depth of the concavity cannot exceed 5/16 deep. The drawing in the rule book shows that.

But of course if you want to make it more than it is have a good time with that.

Robert

And 3/4" wide

Please look at the drawings in the rule book. Look first at the strake drawing then at the concavity drawing..........You will see that the width requirement is listed on the strake drawing but not the concavity drawing. Why do you think that is? Maybe, just maybe, because it does not have a width restriction. Concavity, or hook as you called it, is legal in NAMBA per the section you have quoted.

I am sure this has more to do with trying to bash a specific brand of boat than trying to correct a rule issue. You state that "I my self like to play on a level playing surface." So do you think that a particular brand of boat has a distinct advantage or has unleveled the playing field?

Robert

 

[dwilfong]

The reason no one talks about it is that by the NAMBA rule book many boats are not legal .

IE THE HOOK

I know this will stir the pot.

4. Concavity – When checked with a straight edge at right angles to the keel at any point

​

between the transom and the mid-point of the hull length, no depression, step or

​

concavity will exceed the dimensional limits for strakes.

​

5. Strakes - Regardless of the type or purpose, must conform to the following rules:

​

a. Strakes will be no more than 3/4" wide and 5/16" deep. For hulls over 46"

​

long and a beam width over 15", strakes will be no more than 3/4" wide and

​

1/2" deep.

 

 

David

 

PS I my self like to play on a level playing surface.

The rule does not state that hooks are illegal is states that they will not exceed the (SAME) dimensional limits for strakes. Or in other words, have the same dimensional limits as strakes. For example the depth of the concavity cannot exceed 5/16 deep. The drawing in the rule book shows that.

But of course if you want to make it more than it is have a good time with that.

Robert

And 3/4" wide

Please look at the drawings in the rule book. Look first at the strake drawing then at the concavity drawing..........You will see that the width requirement is listed on the strake drawing but not the concavity drawing. Why do you think that is? Maybe, just maybe, because it does not have a width restriction. Concavity, or hook as you called it, is legal in NAMBA per the section you have quoted.

I am sure this has more to do with trying to bash a specific brand of boat than trying to correct a rule issue. You state that "I my self like to play on a level playing surface." So do you think that a particular brand of boat has a distinct advantage or has unleveled the playing field?

Robert

Just stating what it said in the rule book as for the dimensional limits for the strekes that the concavity can not exceed.

As for the" level playing surface". Was referring to I like the bottom of my boat flat. But that is just my preference. That all.

No bashing intended.

David

 

[Mark Poole ModVP]

If the rule is talking about "at right angles to the keel" then I would think it is to prevent someone from using a hull that is so concave that is a cathedral hull. I don't think this refers to "hook". If your boat has between 5/16 and 1/2" of hook then you have a submarine!

 

[T.S.Davis]

If your boat has between 5/16 and 1/2" of hook then you have a submarine!

haha That makes sense to me.

Sorry guys, I honestly wasn't trying to kick the hive. Not this time at least. I understand the limitations spelled out in the book. I was thinking cathedral....ish. I thought that's what was meant by concavity. I wasn't thinking hook at the time. A really subtle hook I understand. That's how the bottom on Seaducers looks if remember correctly. Barely there.

I was trying to understand the concept of a mild cathedral shape. Subtle. Not a 1" deep cav or some such nonsense. Something you would need a straight edge to check.

 

[Rokieboater]

If the rule is talking about "at right angles to the keel" then I would think it is to prevent someone from using a hull that is so concave that is a cathedral hull. I don't think this refers to "hook". If your boat has between 5/16 and 1/2" of hook then you have a submarine!

Winner, winner, winner.....

Robert

 

[Mark Poole ModVP]

I would think building a mono with lateral concave (from the keel to the chine) would have its good points....and not so good also. It might cut rough water better having a sharper deadrise near the keel. But as the water climbs up the deadrise it could tend to cling to the concave shape which would cause more drag. Properly positioned strakes may solve that problem though. There has also been an on going argument that the vertical sides of strakes cause a low pressure area and thus drag.