i was thinking

[Marty Davis]

Since we are on turn fins, think about this..............When the boat goes straight there is no water coming off the turn fin. When you throw the boat into the corner the fin throws a wall of water up in the air. To do that the fin and boat has to be sliding to the outside of the course. Agreed? Now, if water is being thrown up in the air off the trailing edge of the fin, shouldn't the angle of the trailing edge help to control where that water is thrown. Relate it to a propeller. If you change the rake of the trailing edge doesn't that change the lifting characteristic of the prop. Remember grade school and the law that states for every action there is an equal and OPPOSITE reaction. The water is shooting up, so does that actions/reaction push the sponson down to keep the sponson on the water? Thoughts????

John:

You would think that would be correct. BUT, if you think of the fin as a pivot point and NOT as something that is sliding sideways, you will be talking about the correct fin. One that throws a lot of water into the air is NOT working very well. One that hardly has ANY WATER being thrown in the air is what you are looking for. In fact, you have discovered one of the MOST IMPORTANT testing items in turn fin optimization. The amount of water is the KEY.

What would you say if I asked you how important the location of the the center of pressure of the fin is in relation to the dynamic CG? Would the optimimum position be within 1/2", 1/4", 1/8", 1/16" or ????

Marty Davis

Are we talking sailboats and wings type pressure differences when you say center of pressure or a specific location in the fin?

John:

Do you have Autocad capability? If so, you can convert the shape of the fin area below the water line into a polyline, then to a region and use the Mass Properties to tell you where the center of pressure is. I would think that an easy way of describing the center of pressure would be to describe the place on the fin that if you put the head of a pencil against the fin at 90 degrees it would support the fin against pressure from the other side, still staying supported by the head of the pencil. All different shapes will have a center of pressure that will move as the shape changes. That point on the fin has a DIRECT relationship to the cg. The question that I asked you about the precision of the location of the fin is LESS THEN 1/6". When you hit the perfect position it will totally amaze you in the way the boat acts and lack of drag in the turns. The boat will actually appear to accelerate in the turns. You ONLY need to look at the fin in relation to the area of the fin that is in the water. Sorry, this is getting VERY technical, but in order to understand the dynamics of turn fins, it is required to be this detailed. Lets say that the shape of the fin is similar to one of these random shapes http://www.rcboat.com/cp.jpg The center of pressure is shown on each of them. That point is relative to the cg.

Marty Davis

 

[John Finch]

Marty,

I don't have cad but I just did some measuring using graph paper and If I understand you correctly I have been running my CG at 3/4 inch behind the max pressure point. So are you telling me if I move the turn fin forward at 1/8 inch increments I will find a sweet spot where I will see the boat accellerate in the turns? I remember seeing your hydro do that at the Fort Wayne IMPBA nats. It was impressive. I see my boats do that when they are a bit on the rich side of the needle setting.

 

[Marty Davis]

Marty,I don't have cad but I just did some measuring using graph paper and If I understand you correctly I have been running my CG at 3/4 inch behind the max pressure point. So are you telling me if I move the turn fin forward at 1/8 inch increments I will find a sweet spot where I will see the boat accellerate in the turns? I remember seeing your hydro do that at the Fort Wayne IMPBA nats. It was impressive. I see my boats do that when they are a bit on the rich side of the needle setting.

John:

I can't tell you that will work for you.

The shape of the fin, the area of the fin, the bend of the fin, the placement relative to the cg are all a part of the equation. It took me 3 or 4 years of constant work to work this out. Only until recently when Brian Callahan helped me quantify it, was I able to make it repeat on other boats. We used our analysis to take the optimized fin on my 20 hydro and apply it to his 67 hydro. It was just as impressive as the 20 boat the FIRST day at the pond after minor adjustment (even more so, since it was MUCH faster). I had an idea that I might want to have a fin that was slightly oversize (for the 67 boat) since it was moving at a greater speed. What I found was that the fin that was designed from the 20 hydro was perfect and the fin that was out of proportion oversize, was terrible. This indicated to me that the relationships that we had worked on were correct and optimized. This has given me the ability to design a fin for anything. We are in the initial stages of applying this technology to a new Sport 20, Sport 40, Gas Rigger, 45 hydro. Hopefully you will see all of these boats at the IMPBA Nats.

I had a great fin for my Miss Vernors several years ago, but I wish that I had Miss Vernors now to try this new technology. Maybe we will apply it to Joe Wiebelhaus' 1/8 Scale.

In order to find the optimum position of the fin, you will have to slot the attachment and move it in small amounts 1/16" to find the best position. After that, you can then start to optimize the fin shape and area. Finding the location is super important and can be found as you describe. IF the fin is CLOSE TO the correct shape and area.

Marty

 

[Marty Davis]

Marty,I don't have cad but I just did some measuring using graph paper and If I understand you correctly I have been running my CG at 3/4 inch behind the max pressure point. So are you telling me if I move the turn fin forward at 1/8 inch increments I will find a sweet spot where I will see the boat accellerate in the turns? I remember seeing your hydro do that at the Fort Wayne IMPBA nats. It was impressive. I see my boats do that when they are a bit on the rich side of the needle setting.

John:

I didn't have AutoCAD capability until just fairly recently. I took a 12 hour beginning course at a local university. I wish that I had done this YEARS AGO. It has helped me more than you can imagine. I have my entire boat drawn and can do in depth analysis of so many things as well as use it for scaling up/down anything. I would suggest that any serious rc boat racer goi get the beginner course.

Marty Davis

 

[Tom v.d Brink]

great discussion indeed and i agree with jim when he says it is the best on intlwaters in a while.

I read what you wrote about the turnfin acting as a pivot point and i think it has been exlained like that before in the past.

however from a vehicle dynamics point of view I take a different approach to this as i really can't see a "big flat plate" as a point.

the way i see the turning behavior of a rigger is as follows,

a boat going along a straight line has the velocity vector pointing straight forward. to change direction this needs to be rotated sideways.

as in a car i would expect the boat to develop a slip angle to its original heading the slip angle is of course caused by the rudder snaking the tail as to say.

as the boat has a slip angle it exposes the turnfin sideways into the path of motion. the pressure developed on the inner face of the turnfin causes the turning moment around transfering the motion vector to the right.

I didn't work on the rest of the dynamics of this priciple yet as i am usually more interested in estimating things that go straight.

however i would like you guy's opinion on the theory does it fit your picture of the turning dynamics of the boats?

 

[John Finch]

I wish I could say "see ya at the nats", but I don't know if I can get that much time off. I wish the nats were shorter. Dick Tyndal makes the turn fins that I have been experimenting with. He just lives down the street so to speak. He does such a pretty job with them. I ask him to make a certain size and bend and he makes a mold of sorts to be able to reproduce them. I have build a lot of trial and error fins and then asked Dick to make some pretty ones with the same shape. The ones I build are always ugly! One time I asked for three identical fins and he made them just a bit different. ONLY a bit different. He said try them and let me know what you find. Only the original worked well on the boat. The design that works best on my boats is a take off of the roadrunner. I guess you had something to do with that original design. Is my fin location of 3/4 close to what you are using? Oh, I still have my roundnose Bardahl that I ran in 97 at the nats. It is set up like your Vernors was. Same prop too. If you want to send me a fin I will try it on the boat and let you know if it works better than what I have.

 

[Marty Davis]

great discussion indeed and i agree with jim when he says it is the best on intlwaters in a while.
I read what you wrote about the turnfin acting as a pivot point and i think it has been exlained like that before in the past.

however from a vehicle dynamics point of view I take a different approach to this as i really can't see a "big flat plate" as a point.

the way i see the turning behavior of a rigger is as follows,

a boat going along a straight line has the velocity vector pointing straight forward. to change direction this needs to be rotated sideways.

as in a car i would expect the boat to develop a slip angle to its original heading the slip angle is of course caused by the rudder snaking the tail as to say.

as the boat has a slip angle it exposes the turnfin sideways into the path of motion. the pressure developed on the inner face of the turnfin causes the turning moment around transfering the motion vector to the right.

I didn't work on the rest of the dynamics of this priciple yet as i am usually more interested in estimating things that go straight.

however i would like you guy's opinion on the theory does it fit your picture of the turning dynamics of the boats?

Tom:

I agree with your analysis... BUT the turn fin is not a BIG flat plate. It is only large enough to minimize side slip. That is the reason that the water coming up and off the fin defines the efficiency of the fin. There is no doubt that there is side slip, it is just to our benefit to minimize it and make it more of a pivoting motion between the turn fin and the rudder.

Marty Davis

 

[John Finch]

Marty,

My most recent rigger. This years model. The cg is 1 3/4 inches behind the pressure point. It appears to be faster and much smoother than last years boat. Strictly an observation. Which boat is closer to your findings?

 

[Marty Davis]

I wish I could say "see ya at the nats", but I don't know if I can get that much time off. I wish the nats were shorter. Dick Tyndal makes the turn fins that I have been experimenting with. He just lives down the street so to speak. He does such a pretty job with them. I ask him to make a certain size and bend and he makes a mold of sorts to be able to reproduce them. I have build a lot of trial and error fins and then asked Dick to make some pretty ones with the same shape. The ones I build are always ugly! One time I asked for three identical fins and he made them just a bit different. ONLY a bit different. He said try them and let me know what you find. Only the original worked well on the boat. The design that works best on my boats is a take off of the roadrunner. I guess you had something to do with that original design. Is my fin location of 3/4 close to what you are using? Oh, I still have my roundnose Bardahl that I ran in 97 at the nats. It is set up like your Vernors was. Same prop too. If you want to send me a fin I will try it on the boat and let you know if it works better than what I have.

John:

MOST of the fins that I made in the effort to optimize were UGLY. No reason to make them all look good since they won't be on the boat long anyway. The next one is already in my head.....

Some people can't stand to make ANYTHING UGLY, but since time is so limited, I have ZERO problem not finishing them completely. I would suggest that people use that approach so that they can cover more ground quickly.

Your question can not be answered directly, since all boats are different in their proportions. Also, the cg varies with a full tank, an empty tank or one that is 1/2 full. Now that I understand the dynamics, I can use any of these cg points.

We are getting into an area that has taken me a LONG time to figure out and I am not comfortable talking in very specific terms. I would like to give information that will save people time in their own general search.

Marty Davis

 

[John Finch]

I wish I could say "see ya at the nats", but I don't know if I can get that much time off. I wish the nats were shorter. Dick Tyndal makes the turn fins that I have been experimenting with. He just lives down the street so to speak. He does such a pretty job with them. I ask him to make a certain size and bend and he makes a mold of sorts to be able to reproduce them. I have build a lot of trial and error fins and then asked Dick to make some pretty ones with the same shape. The ones I build are always ugly! One time I asked for three identical fins and he made them just a bit different. ONLY a bit different. He said try them and let me know what you find. Only the original worked well on the boat. The design that works best on my boats is a take off of the roadrunner. I guess you had something to do with that original design. Is my fin location of 3/4 close to what you are using? Oh, I still have my roundnose Bardahl that I ran in 97 at the nats. It is set up like your Vernors was. Same prop too. If you want to send me a fin I will try it on the boat and let you know if it works better than what I have.

John:

MOST of the fins that I made in the effort to optimize were UGLY. No reason to make them all look good since they won't be on the boat long anyway. The next one is already in my head.....

Some people can't stand to make ANYTHING UGLY, but since time is so limited, I have ZERO problem not finishing them completely. I would suggest that people use that approach so that they can cover more ground quickly.

Your question can not be answered directly, since all boats are different in their proportions. Also, the cg varies with a full tank, an empty tank or one that is 1/2 full. Now that I understand the dynamics, I can use any of these cg points.

We are getting into an area that has taken me a LONG time to figure out and I am not comfortable talking in very specific terms. I would like to give information that will save people time in their own general search.

Marty Davis

I understand. I will put this out there.................Marty brought up a very good point. Boat setup varies with how the boat is weighted at the time of the measurement. For example......If you put your boat on a flat table (setup board) and measure sponson angles for example. You will get a different reading when the boat has the engine in it as opposed to not having the engine in the hull. TWO COMPLETELY DIFFERENT MEASUREMENTS. If you don't believe it......try it!

 

[Marty Davis]

I wish I could say "see ya at the nats", but I don't know if I can get that much time off. I wish the nats were shorter. Dick Tyndal makes the turn fins that I have been experimenting with. He just lives down the street so to speak. He does such a pretty job with them. I ask him to make a certain size and bend and he makes a mold of sorts to be able to reproduce them. I have build a lot of trial and error fins and then asked Dick to make some pretty ones with the same shape. The ones I build are always ugly! One time I asked for three identical fins and he made them just a bit different. ONLY a bit different. He said try them and let me know what you find. Only the original worked well on the boat. The design that works best on my boats is a take off of the roadrunner. I guess you had something to do with that original design. Is my fin location of 3/4 close to what you are using? Oh, I still have my roundnose Bardahl that I ran in 97 at the nats. It is set up like your Vernors was. Same prop too. If you want to send me a fin I will try it on the boat and let you know if it works better than what I have.

John:

MOST of the fins that I made in the effort to optimize were UGLY. No reason to make them all look good since they won't be on the boat long anyway. The next one is already in my head.....

Some people can't stand to make ANYTHING UGLY, but since time is so limited, I have ZERO problem not finishing them completely. I would suggest that people use that approach so that they can cover more ground quickly.

Your question can not be answered directly, since all boats are different in their proportions. Also, the cg varies with a full tank, an empty tank or one that is 1/2 full. Now that I understand the dynamics, I can use any of these cg points.

We are getting into an area that has taken me a LONG time to figure out and I am not comfortable talking in very specific terms. I would like to give information that will save people time in their own general search.

Marty Davis

I understand. I will put this out there.................Marty brought up a very good point. Boat setup varies with how the boat is weighted at the time of the measurement. For example......If you put your boat on a flat table (setup board) and measure sponson angles for example. You will get a different reading when the boat has the engine in it as opposed to not having the engine in the hull. TWO COMPLETELY DIFFERENT MEASUREMENTS. If you don't believe it......try it!

John:

The amount of specific information that we have talked about should provide a GREAT starting point for people to do their own analysis, boat building and testing. It would be great to have this type discussion on a variety of things. We used to have Chats and discussions like this on my RcBoat.com Listbot.

Maybe we can do more of this. I have REALLY enjoyed it.

Of course, we have but scratched the surface on this topic, so I would bet that it won't die at this point.

Marty Davis

 

[izitbrokeyet?]

Verry C000L.....a real thread.

solid

maybe this forum isn't D.O.A. afterall

 

[Charles Perdue]

I wish I could say "see ya at the nats", but I don't know if I can get that much time off. I wish the nats were shorter. Dick Tyndal makes the turn fins that I have been experimenting with. He just lives down the street so to speak. He does such a pretty job with them. I ask him to make a certain size and bend and he makes a mold of sorts to be able to reproduce them. I have build a lot of trial and error fins and then asked Dick to make some pretty ones with the same shape. The ones I build are always ugly! One time I asked for three identical fins and he made them just a bit different. ONLY a bit different. He said try them and let me know what you find. Only the original worked well on the boat. The design that works best on my boats is a take off of the roadrunner. I guess you had something to do with that original design. Is my fin location of 3/4 close to what you are using? Oh, I still have my roundnose Bardahl that I ran in 97 at the nats. It is set up like your Vernors was. Same prop too. If you want to send me a fin I will try it on the boat and let you know if it works better than what I have.

John:

MOST of the fins that I made in the effort to optimize were UGLY. No reason to make them all look good since they won't be on the boat long anyway. The next one is already in my head.....

Some people can't stand to make ANYTHING UGLY, but since time is so limited, I have ZERO problem not finishing them completely. I would suggest that people use that approach so that they can cover more ground quickly.

Your question can not be answered directly, since all boats are different in their proportions. Also, the cg varies with a full tank, an empty tank or one that is 1/2 full. Now that I understand the dynamics, I can use any of these cg points.

We are getting into an area that has taken me a LONG time to figure out and I am not comfortable talking in very specific terms. I would like to give information that will save people time in their own general search.

Marty Davis

I understand. I will put this out there.................Marty brought up a very good point. Boat setup varies with how the boat is weighted at the time of the measurement. For example......If you put your boat on a flat table (setup board) and measure sponson angles for example. You will get a different reading when the boat has the engine in it as opposed to not having the engine in the hull. TWO COMPLETELY DIFFERENT MEASUREMENTS. If you don't believe it......try it!

John:

The amount of specific information that we have talked about should provide a GREAT starting point for people to do their own analysis, boat building and testing. It would be great to have this type discussion on a variety of things. We used to have Chats and discussions like this on my RcBoat.com Listbot.

Maybe we can do more of this. I have REALLY enjoyed it.

Of course, we have but scratched the surface on this topic, so I would bet that it won't die at this point.

Marty Davis

Ok, here goes my 2 cents worth on using angled flat turn fins.

The first time that the ANGLED flat turn fin was used in serious competition, to the best of my knowledge, was on one of Marty's 40 Crapshooters that we ran at the NAMBA Nationals in Monterey California in 1979. This and other modifications ( the beginning of the BOSS setup) was very successful. We won the 40 hydro class with a perfect score. Marty you and some of your friends from Indy were there, you should remember the maroon and gold boat.

The boat worked ok but there was room for improvements. On the trip back from that race, in the motor home,the BOSS design was expanded to include some improvements that were needed to help

the boat turn better and more consistent in different water conditions. The BOSS boat was born.

It took about a year to get the bugs worked out of the design. The first BOSS was a 20 size. In 1981 we won the district 19 championship (not finishing in first place only twice all year) and also won the 20 hydro class at the NAMBA Nationals at Amarillo, TX with 4 first place heats and fast time in the class. All this using an angled flat turn fin.

Jack O'Donnell, Steve O'Donnell and myself took a weeks vacation and built the 60 BOSS from scratch using what was learned from the 20 and 40 BOSS(You may be asking what about the 40 BOSS. It had 2 first place heat wins in Amarillo when a rudder servo decided to go out of off bouy 5 and I think it still holds the record for going the deepest into the bank at that lake, in past the sponsons). Only about a month after the 60 BOSS was built, Jack and Steve took it back to Indy for the record trials. The first lap of the 2 lap timed oval was run at about 10 seconds. The disc rotor in the engine went out on the second lap and the boat slowed considerably and the still broke the old record by about 2 seconds. The boat was over-built as for strength and it weighed in at 9 1/2 pounds. All this and it was done using an angled flat turn fin.

There is more to using this type of turn fin than just bolting it on. The entire boat and engine combinations has to be designed around it to optimize its benefits.

Whether it is better than the curved turn fin, I don't know since I sent all of my time on the angled flat design. Each design has its good points and bad points. You just can't count either of them out.

Marty, I enjoy reading your comments, and John, I enjoyed reading your articles and your books, you guys keep up the good work passing along your great knowledge about RC boating.

 

[John Finch]

My wife just opened up the pool this morning so let me just add one thing to help the experimenters. The cg of you rigger will change at least one inch with a full vs empty tank if the tank is in front of the engine. High nitro fuel weighs more than low nitro fuel. Nitro weighs more than methanol. So be consistent when you check cg's and table the boat. Have fun.

 

[Marty Davis]

My wife just opened up the pool this morning so let me just add one thing to help the experimenters. The cg of you rigger will change at least one inch with a full vs empty tank if the tank is in front of the engine. High nitro fuel weighs more than low nitro fuel. Nitro weighs more than methanol. So be consistent when you check cg's and table the boat. Have fun.

I would suggest that you use the 1/2 full fuel tank as your cg point. That is a good compromise and will serve you well.

Marty Davis

 

[SCOTT WITHERELL]

I wasn't sure what angle to put on my sponsons ride pad on my scratch built sport 40 ,so I made them removeable to change the angles, by makin ride pads seperat with( incedenets and dehedrel)bolt on type.

 

[Marty Davis]

I wish I could say "see ya at the nats", but I don't know if I can get that much time off. I wish the nats were shorter. Dick Tyndal makes the turn fins that I have been experimenting with. He just lives down the street so to speak. He does such a pretty job with them. I ask him to make a certain size and bend and he makes a mold of sorts to be able to reproduce them. I have build a lot of trial and error fins and then asked Dick to make some pretty ones with the same shape. The ones I build are always ugly! One time I asked for three identical fins and he made them just a bit different. ONLY a bit different. He said try them and let me know what you find. Only the original worked well on the boat. The design that works best on my boats is a take off of the roadrunner. I guess you had something to do with that original design. Is my fin location of 3/4 close to what you are using? Oh, I still have my roundnose Bardahl that I ran in 97 at the nats. It is set up like your Vernors was. Same prop too. If you want to send me a fin I will try it on the boat and let you know if it works better than what I have.

John:

MOST of the fins that I made in the effort to optimize were UGLY. No reason to make them all look good since they won't be on the boat long anyway. The next one is already in my head.....

Some people can't stand to make ANYTHING UGLY, but since time is so limited, I have ZERO problem not finishing them completely. I would suggest that people use that approach so that they can cover more ground quickly.

Your question can not be answered directly, since all boats are different in their proportions. Also, the cg varies with a full tank, an empty tank or one that is 1/2 full. Now that I understand the dynamics, I can use any of these cg points.

We are getting into an area that has taken me a LONG time to figure out and I am not comfortable talking in very specific terms. I would like to give information that will save people time in their own general search.

Marty Davis

I understand. I will put this out there.................Marty brought up a very good point. Boat setup varies with how the boat is weighted at the time of the measurement. For example......If you put your boat on a flat table (setup board) and measure sponson angles for example. You will get a different reading when the boat has the engine in it as opposed to not having the engine in the hull. TWO COMPLETELY DIFFERENT MEASUREMENTS. If you don't believe it......try it!

John:

The amount of specific information that we have talked about should provide a GREAT starting point for people to do their own analysis, boat building and testing. It would be great to have this type discussion on a variety of things. We used to have Chats and discussions like this on my RcBoat.com Listbot.

Maybe we can do more of this. I have REALLY enjoyed it.

Of course, we have but scratched the surface on this topic, so I would bet that it won't die at this point.

Marty Davis

Ok, here goes my 2 cents worth on using angled flat turn fins.

The first time that the ANGLED flat turn fin was used in serious competition, to the best of my knowledge, was on one of Marty's 40 Crapshooters that we ran at the NAMBA Nationals in Monterey California in 1979. This and other modifications ( the beginning of the BOSS setup) was very successful. We won the 40 hydro class with a perfect score. Marty you and some of your friends from Indy were there, you should remember the maroon and gold boat.

The boat worked ok but there was room for improvements. On the trip back from that race, in the motor home,the BOSS design was expanded to include some improvements that were needed to help

the boat turn better and more consistent in different water conditions. The BOSS boat was born.

It took about a year to get the bugs worked out of the design. The first BOSS was a 20 size. In 1981 we won the district 19 championship (not finishing in first place only twice all year) and also won the 20 hydro class at the NAMBA Nationals at Amarillo, TX with 4 first place heats and fast time in the class. All this using an angled flat turn fin.

Jack O'Donnell, Steve O'Donnell and myself took a weeks vacation and built the 60 BOSS from scratch using what was learned from the 20 and 40 BOSS(You may be asking what about the 40 BOSS. It had 2 first place heat wins in Amarillo when a rudder servo decided to go out of off bouy 5 and I think it still holds the record for going the deepest into the bank at that lake, in past the sponsons). Only about a month after the 60 BOSS was built, Jack and Steve took it back to Indy for the record trials. The first lap of the 2 lap timed oval was run at about 10 seconds. The disc rotor in the engine went out on the second lap and the boat slowed considerably and the still broke the old record by about 2 seconds. The boat was over-built as for strength and it weighed in at 9 1/2 pounds. All this and it was done using an angled flat turn fin.

There is more to using this type of turn fin than just bolting it on. The entire boat and engine combinations has to be designed around it to optimize its benefits.

Whether it is better than the curved turn fin, I don't know since I sent all of my time on the angled flat design. Each design has its good points and bad points. You just can't count either of them out.

Marty, I enjoy reading your comments, and John, I enjoyed reading your articles and your books, you guys keep up the good work passing along your great knowledge about RC boating.

Charles:

Yes, I sure remember coming the NAMBA Nats in Monterey. It was a really fun time for us. We also enjoyed a small earthquake just for us. That was the Nats that Jack Garcia left his boat on the dryer at home and didn't realize it till he got to Monterey. Good times....

I remember Steve and Jack showing up for the Hydro Masters. That is in fact, what got me started on turn fins and how much they could contribute to the ability of a boat to be AWESOME. As I remember, the fin that they were using was a flat fin with the bottom of the fin perfectly flat. They indicated that the flat area on the bottom of the fin was important, but I never figured that out.

We spend a lot of time with the flat fin and couldn't get past the left turn problem. That is when we moved to a fin that was 90 degrees to the water with the bend just as far toward the bottom as we could get. That way we eliminated the left turn problem. In fact, I was tempted this year to enter my 20 hydro in Open Offshore class where you have to turn left. I was not well received in my attempt to enter it in that class. The 20 boat will turn left just fine and I could race where I had to turn left.

I will tell you a little story about the Hydro Masters that year. Steve brought a 40 and a 60 boat. We sanctioned the qualifications so that any times that were records would be official. Gregg Huey set the 40 oval time and Steve came back and took it away from him with an amazing time. The 60 boat was having some trouble with consistency. Steve made the A Main in both classes. He had the 60 boat set up so that he could turn right, but had little ability to turn left. In fact he had a flex cable arrangement hooked to the rudder and when pushing it was supposed to turn left. The flex cable did not allow him to turn left much at all. In the A Main there were 7 boats so he found himself in bad situations where he needed to be able to turn left and could not. I don't think that he finished a heat. The boat was amazing, but the problem with the left turn, kept him from doing well.

As I remember, the boat also had air traps on the bottom of the sponsons. Gregg Huey bought Crapshooter from me shortly after that time and produced some Crapshooter with the air traps. I never did really study that feature and to this day do not know if it was good or bad. I was so interested in the turn fins that I kind of left that alone and concentrated on the turning.

We would be interested in seeing any pictures of your new efforts, as I can guarantee everyone that they will be "cutting edge".

Marty Davis

 

[Marty Davis]

I wasn't sure what angle to put on my sponsons ride pad on my scratch built sport 40 ,so I made them removeable to change the angles, by makin ride pads seperat with( incedenets and dehedrel)bolt on type.

Good job, that will allow you to experiment. Be sure to make the edges VERY SHARP. It will give you much more speed.

Marty Davis

 

[SCOTT WITHERELL]

the ride pads will be sheeted with 1/16 carbon fiber

 

[John Finch]

Neat idea!