compensating for too much lift

[Rick Cesati]

Gentlemen,

For some time, I have been battling what I feel like is too much lift in my 21 mono. The reason I think this is becuase my racing partner and I have the identical boats (4 strake microburst) setup with idenitcal hardware and fuel tank location. CGs are very close as well, the only major difference is in the motor, I run a NR, he runs a MAC. Props are intercangable on the boats as well (X437/3). Several months ago, we noticed the boats have different dead rise angles, his is significantly steeper than mine (an earlier generation boat) and consequently has a small freeboard. I cannot remember the angles right now.

Not surprisingly, his boat behaves better in rough water, but the real difference is the point at which the hull blows off. His will run hard well into the mid 50s in true race water, while mine will readily blow off before it reaches 50 mph. I have tried repeatedly to correct the problem including three different sets of tabs and myriad CG locations. I will admit to being stubborn about adding weight to the boat or angle to the strut, although I have tried to raise the strut to settle the boat will little to no affect. Perhaps my CG should be further forward than his? Will changing to a mutliple tank setup help when this is established in order to stabilze the CG? What about the CA trick on the hull bottom?

Thoughts, comments and suggestions welcome as I am trying to expand my mono knowledge.

Rick

 

[Joe Warren]

Gentlemen,
For some time, I have been battling what I feel like is too much lift in my 21 mono. The reason I think this is becuase my racing partner and I have the identical boats (4 strake microburst) setup with idenitcal hardware and fuel tank location. CGs are very close as well, the only major difference is in the motor, I run a NR, he runs a MAC. Props are intercangable on the boats as well (X437/3). Several months ago, we noticed the boats have different dead rise angles, his is significantly steeper than mine (an earlier generation boat) and consequently has a small freeboard. I cannot remember the angles right now.

Not surprisingly, his boat behaves better in rough water, but the real difference is the point at which the hull blows off. His will run hard well into the mid 50s in true race water, while mine will readily blow off before it reaches 50 mph. I have tried repeatedly to correct the problem including three different sets of tabs and myriad CG locations. I will admit to being stubborn about adding weight to the boat or angle to the strut, although I have tried to raise the strut to settle the boat will little to no affect. Perhaps my CG should be further forward than his? Will changing to a mutliple tank setup help when this is established in order to stabilze the CG? What about the CA trick on the hull bottom?

Thoughts, comments and suggestions welcome as I am trying to expand my mono knowledge.

Rick

Rick You would want to lower the Strut to tighten the boat up on the water.( this allows the prop to lift more since it is now deeper in the water, this will plant the front breaking point of the boat to the water.). also check the length & the size of the rudder blade. Just a little longer blade or a little larger blade may do the trick. it dont take much of either. also Keep the main tank as close to the engine as possible. this keeps the CG from changing so much when it burns the fuel off. Also practice like you race. 2-3 mills laps 6 race laps & check the balance on the boat. Some of the fuel will remain under race conditons to act as ballast in the hull. also carefully look @ how the trim plates are mounted on each hull. The water spraying off the strakes (leaving the hull) is the water you would like to run across the trim plates to keep the rear lifted & stable. This same water is already exting the hull, its nice to use it for something before it falls back into the lake. Also Make sure you not modifying the props to kill the lift. Working on the trailing edges( to change the spray angle) will hurt the ability of the prop to lift. Hope this helps? Microburst built many diff versions of the 20 mono maybe as many as 4-5 The later hulls were the better hulls. some of the earlier hulls chine walked a lot. Chris Fabbro Orginal owner of Microburst was a Mono Hull Master builder. He had a lot of hull experience & could tweak a hull & hardware. It is a shame he got out of the hobby.....jw

 

[Rick Cesati]

Gentlemen,
For some time, I have been battling what I feel like is too much lift in my 21 mono. The reason I think this is becuase my racing partner and I have the identical boats (4 strake microburst) setup with idenitcal hardware and fuel tank location. CGs are very close as well, the only major difference is in the motor, I run a NR, he runs a MAC. Props are intercangable on the boats as well (X437/3). Several months ago, we noticed the boats have different dead rise angles, his is significantly steeper than mine (an earlier generation boat) and consequently has a small freeboard. I cannot remember the angles right now.

Not surprisingly, his boat behaves better in rough water, but the real difference is the point at which the hull blows off. His will run hard well into the mid 50s in true race water, while mine will readily blow off before it reaches 50 mph. I have tried repeatedly to correct the problem including three different sets of tabs and myriad CG locations. I will admit to being stubborn about adding weight to the boat or angle to the strut, although I have tried to raise the strut to settle the boat will little to no affect. Perhaps my CG should be further forward than his? Will changing to a mutliple tank setup help when this is established in order to stabilze the CG? What about the CA trick on the hull bottom?

Thoughts, comments and suggestions welcome as I am trying to expand my mono knowledge.

Rick

Rick You would want to lower the Strut to tighten the boat up on the water.( this allows the prop to lift more since it is now deeper in the water, this will plant the front breaking point of the boat to the water.). also check the length & the size of the rudder blade. Just a little longer blade or a little larger blade may do the trick. it dont take much of either. also Keep the main tank as close to the engine as possible. this keeps the CG from changing so much when it burns the fuel off. Also practice like you race. 2-3 mills laps 6 race laps & check the balance on the boat. Some of the fuel will remain under race conditons to act as ballast in the hull. also carefully look @ how the trim plates are mounted on each hull. The water spraying off the strakes (leaving the hull) is the water you would like to run across the trim plates to keep the rear lifted & stable. This same water is already exting the hull, its nice to use it for something before it falls back into the lake. Also Make sure you not modifying the props to kill the lift. Working on the trailing edges( to change the spray angle) will hurt the ability of the prop to lift. Hope this helps? Microburst built many diff versions of the 20 mono maybe as many as 4-5 The later hulls were the better hulls. some of the earlier hulls chine walked a lot. Chris Fabbro Orginal owner of Microburst was a Mono Hull Master builder. He had a lot of hull experience & could tweak a hull & hardware. It is a shame he got out of the hobby.....jw

Joe,

Thanks for the info. With regard to the rudder blade, does rounding the bottom reduce the lift like on a hydro?

R-

 

[Rigged]

Joe,
Thanks for the info. With regard to the rudder blade, does rounding the bottom reduce the lift like on a hydro?

R-

Ive been told it does, and ive always rounded the bottoms of my rudders, but i recently switched to a new blade (after bending one) that was stock and really cannot see any difference at all in how the boat performed.

Maybe it being a 45 inch gas boat it doesnt have a big effect as on a small 21 size mono ?

 

[Joe Warren]

Gentlemen,
For some time, I have been battling what I feel like is too much lift in my 21 mono. The reason I think this is becuase my racing partner and I have the identical boats (4 strake microburst) setup with idenitcal hardware and fuel tank location. CGs are very close as well, the only major difference is in the motor, I run a NR, he runs a MAC. Props are intercangable on the boats as well (X437/3). Several months ago, we noticed the boats have different dead rise angles, his is significantly steeper than mine (an earlier generation boat) and consequently has a small freeboard. I cannot remember the angles right now.

Not surprisingly, his boat behaves better in rough water, but the real difference is the point at which the hull blows off. His will run hard well into the mid 50s in true race water, while mine will readily blow off before it reaches 50 mph. I have tried repeatedly to correct the problem including three different sets of tabs and myriad CG locations. I will admit to being stubborn about adding weight to the boat or angle to the strut, although I have tried to raise the strut to settle the boat will little to no affect. Perhaps my CG should be further forward than his? Will changing to a mutliple tank setup help when this is established in order to stabilze the CG? What about the CA trick on the hull bottom?

Thoughts, comments and suggestions welcome as I am trying to expand my mono knowledge.

Rick

Rick You would want to lower the Strut to tighten the boat up on the water.( this allows the prop to lift more since it is now deeper in the water, this will plant the front breaking point of the boat to the water.). also check the length & the size of the rudder blade. Just a little longer blade or a little larger blade may do the trick. it dont take much of either. also Keep the main tank as close to the engine as possible. this keeps the CG from changing so much when it burns the fuel off. Also practice like you race. 2-3 mills laps 6 race laps & check the balance on the boat. Some of the fuel will remain under race conditons to act as ballast in the hull. also carefully look @ how the trim plates are mounted on each hull. The water spraying off the strakes (leaving the hull) is the water you would like to run across the trim plates to keep the rear lifted & stable. This same water is already exting the hull, its nice to use it for something before it falls back into the lake. Also Make sure you not modifying the props to kill the lift. Working on the trailing edges( to change the spray angle) will hurt the ability of the prop to lift. Hope this helps? Microburst built many diff versions of the 20 mono maybe as many as 4-5 The later hulls were the better hulls. some of the earlier hulls chine walked a lot. Chris Fabbro Orginal owner of Microburst was a Mono Hull Master builder. He had a lot of hull experience & could tweak a hull & hardware. It is a shame he got out of the hobby.....jw

Joe,

Thanks for the info. With regard to the rudder blade, does rounding the bottom reduce the lift like on a hydro?

R-

I normally round the bottom edge of the rudder blade. If you really want to know the difference of the 2 hulls ?? Take a straight edge measure from the transom towards the front of the boat hull about 1/4 inch outside of the keel. At the point the boat is Not flat is the breaking point on that paticular hull. Measure the other hull & compare....... The C/G is critical in relationship to the beaking point on the hull. This is true on most mono that Do Not have a Hook type Bottom.(seaducer) does not apply to this type measurment.

 

[GRoth265]

One thing you did not mention was if you put a straight edge on the bottom of the two boats. Sometimes glass boats will get a Hollow on the bottom. This will change the boat drastically. (blue print the bottom) especially the last 40% and make sure your riding surface is dead flat. Greg

 

[Joe Warren]

One thing you did not mention was if you put a straight edge on the bottom of the two boats. Sometimes glass boats will get a Hollow on the bottom. This will change the boat drastically. (blue print the bottom) especially the last 40% and make sure your riding surface is dead flat. Greg

Some of the best Tricks for the mono hulls..... especially the 20 hulls is.... Take time to sharpen the strakes & if the mfger intended for the hull to be flat make sure you dont do anything to disturb that....... such as leaving them tied down for days in a poor boat stand, Or stored in excessive heat.. (trailers). Also (using excessive hardner to kick the resin to install the stuffing tube mount )This will heat up a small area & suck up a critical area of the ride pad. If you give up on an older Micro hull?? The Seaducer & Speedmaster are the Current top quality 20 race hull & they have been Greatly improved over the current hull you are working with....jw

 

[Rick Cesati]

One thing you did not mention was if you put a straight edge on the bottom of the two boats. Sometimes glass boats will get a Hollow on the bottom. This will change the boat drastically. (blue print the bottom) especially the last 40% and make sure your riding surface is dead flat. Greg

Some of the best Tricks for the mono hulls..... especially the 20 hulls is.... Take time to sharpen the strakes & if the mfger intended for the hull to be flat make sure you dont do anything to disturb that....... such as leaving them tied down for days in a poor boat stand, Or stored in excessive heat.. (trailers). Also (using excessive hardner to kick the resin to install the stuffing tube mount )This will heat up a small area & suck up a critical area of the ride pad. If you give up on an older Micro hull?? The Seaducer & Speedmaster are the Current top quality 20 race hull & they have been Greatly improved over the current hull you are working with....jw

Joe,

This IS the latest microburst. I gave up on the two strake designs some time ago. FWIW, we are pushing these hulls hard. The Seaducers are great, but also have problems when pushed this hard...my other buddy has 9 oz in his just to keep it on the water! It seems to me there is room for a new 20 mono design that can handle the power of these smaller motors IN RACE WATER!

That said, Joe, can you describe the relationship between CG and breaking point of the hull?

Thanks,

R-

 

[Joe Warren]

One thing you did not mention was if you put a straight edge on the bottom of the two boats. Sometimes glass boats will get a Hollow on the bottom. This will change the boat drastically. (blue print the bottom) especially the last 40% and make sure your riding surface is dead flat. Greg

Some of the best Tricks for the mono hulls..... especially the 20 hulls is.... Take time to sharpen the strakes & if the mfger intended for the hull to be flat make sure you dont do anything to disturb that....... such as leaving them tied down for days in a poor boat stand, Or stored in excessive heat.. (trailers). Also (using excessive hardner to kick the resin to install the stuffing tube mount )This will heat up a small area & suck up a critical area of the ride pad. If you give up on an older Micro hull?? The Seaducer & Speedmaster are the Current top quality 20 race hull & they have been Greatly improved over the current hull you are working with....jw

Joe,

This IS the latest microburst. I gave up on the two strake designs some time ago. FWIW, we are pushing these hulls hard. The Seaducers are great, but also have problems when pushed this hard...my other buddy has 9 oz in his just to keep it on the water! It seems to me there is room for a new 20 mono design that can handle the power of these smaller motors IN RACE WATER!

That said, Joe, can you describe the relationship between CG and breaking point of the hull?

Thanks,

R-

When you find the breaking point then you need to find the C/G. That is the real difference, of the different designs, Free board sides high help with the ability to corner well & handle rough water. The few times I have seen a hull that was extremely hard to get a handle on Especially a Loose hull. I found the problem with the rudder blade. Double check everything you are dragging in the water. A slight bent rudder blade or a blade that is not mounted straight have a huge effect on the hull @ High speeds. Most of the Current hulls are Wild @ on the ragged edge @ anything over 57-58 mph on a quality radar gun... If you must add weight to handle the high speeds in rough water. its best to tie it onto the floatation & try to keep it in the right front nose of the boat. You can add a minium amount & effect the ride the most in that location. P.s the Breaking point will always be in front of the C/G, A longer breaking point (from the C/G point) will be a wetter hull.

 

[Brian Sorgente]

Poor guy... Just cant catch me... (Im the other guy with the same hull) Thanks for all your advice, we've never really looked at the breaking point. When we compare them we'll let you know what we come up with. The pitty of all of this is, if we do actually figure this out, Im gonna have to work a whole lot harder haha

Brian

 

[Rick Cesati]

Poor guy... Just cant catch me...

a$$

 

[Roxyflash]

Poor guy... Just cant catch me...

a$$

I would add soom stick on weights on the top of nose just to see if it helps.

 

[Rick Cesati]

P.s the Breaking point will always be in front of the C/G, A longer breaking point (from the C/G point) will be a wetter hull.

Joe...this is all very interesting. We measured the two hulls, and found the breaking point on the better handlng hull to be more than two inches longer (currently the CGs are very similar). Based on you comment above, should the CG be moved back to make the hull with the shorter breaking point run more wet? This seems counterintuative to me?!?

R-

 

[Rick Cesati]

bump...Joe?

 

[Walt Barney]

bump...Joe?

Rick,

Joe has been in e-ville racing.

Walt Barney