Ski's on old style rear sponson riggers

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PaulHail

PaulHail

Well-Known Member
Joined
Mar 30, 2017
Messages
357
Has anyone replaced the rear sponsons on an old style rigger with a ski, and what are the pro's and con's of the swap.
 
Last edited by a moderator:
I put a rear ski on my 45 Jag it helped to launch the boat and I found I could run a larger prop with it.

Sent from my iPhone using Tapatalk
 
The ski will work on all boats to a certain extent. But it's not simply plug and play to have it work well. The ski will have to be adjusted to work on the boat or the boat to work with ski. Or both.

The ski goes way back in r/c boat history. Marty Davis Crapshooters of the late 1970's used a ski.

Back in the day, my wife, Donna raced a K&B powered M.D. Crapshooter .21. It easily pulled a 1455 with an 8" pipe on 40%.

A couple of years later (1987) Donna won the Orlando Winternats with a .21 Mongoose that also used a ski against a field of 35 boats. Most of which were two rear sponson boats.

That Mongoose also used a .150" flex shaft that ran in an "S" bend tube. Jim Fetters and Ed Hugey were using and promoting the S bend Flex shaft system back in the early 1970's. Maybe even before that.

The bottom of the Mongoose tub was also Flat. The fast guys of that era, told me that would not work. They were all using recurved bottoms on the tubs.

I continued with Flat bottoms until 1996. The Eagle SG design used the recurve bottom and continues to present. I think current Crapshooters and Roadrunners are using flat bottoms along with others.

Both bottoms have benefits, but my 40 years of r/c boating experience says the recurve bottom is best for rough water racing conditions.

I forgot to mention. The 1996 Eagle SG was a two rear sponson boat. We put a ski and no rear sponsons on the SG in 1998 to help engines that had launching problems. The single engine SGX boat regained the two rear sponsons along with the ski. That set up set provided the best handling in all conditions. It set many records and won countless major races. The Twin SGX boats used a ski on each shaft and no rear sponsons.

In recent years we have set up the SGX with just two rear sponsons. That set up also works well with the correct power plant.

The red 1986 Mongoose pictured below also used the ski along with two rear sponsons.

1986 Mongoose 21.jpg
 
Last edited by a moderator:
My last fiber riggers (nitro and gas) work great with a ski..the gas one originally had a recurved botton.....test is the only way to figured out if it works or not.
 
Andy Brown said:
The ski will work on all boats to a certain extent. But it's not simply plug and play to have it work well. The ski will have to be adjusted to work on the boat or the boat to work with ski. Or both.

The ski goes way back in r/c boat history. Marty Davis Crapshooters of the late 1970's used a ski.

Back in the day, my wife, Donna raced a K&B powered M.D. Crapshooter .21. It easily pulled a 1455 with an 8" pipe on 40%.

A couple of years later (1987) Donna won the Orlando Winternats with a .21 Mongoose that also used a ski against a field of 35 boats. Most of which were two rear sponson boats.

That Mongoose also used a .150" flex shaft that ran in an "S" bend tube. Jim Fetters and Ed Hugey were using and promoting the S bend Flex shaft system back in the early 1970's. Maybe even before that.

The bottom of the Mongoose tub was also Flat. The fast guys of that era, told me that would not work. They were all using recurved bottoms on the tubs.

I continued with Flat bottoms until 1996. The Eagle SG design used the recurve bottom and continues to present. I think current Crapshooters and Roadrunners are using flat bottoms along with others.

Both bottoms have benefits, but my 40 years of r/c boating experience says the recurve bottom is best for rough water racing conditions.

I forgot to mention. The 1996 Eagle SG was a two rear sponson boat. We put a ski and no rear sponsons on the SG in 1998 to help engines that had launching problems. The single engine SGX boat regained the two rear sponsons along with the ski. That set up set provided the best handling in all conditions. It set many records and won countless major races. The Twin SGX boats used a ski on each shaft and no rear sponsons.

In recent years we have set up the SGX with just two rear sponsons. That set up also works well with the correct power plant.

The red 1986 Mongoose pictured below also used the ski along with two rear sponsons.
Click to expand...
Thats some good info there Andy. I have found the same results playing with the recurve bottom in regards handling in race conditions.I'm finally starting to play around with a combination ski and rear sponson on the back. First test went very well.

Back in the 80's when we had hard shaft boats, Dad and I were putting a ski on, but we didn't know what we were doing in regards to helping the boat pull prop. We were just trying to keep the hard shaft tube from coming loose due to the vibration. Now we know why we were pulling big props back then.
 
Hi,

i like ski as it will set a hard good ,stable point of running for a boat and you can adjust the high of the propeller. For the ski i use a realy flat plate ,today 1,5mm to 2mm cabon plate is stiff enough. Left an right from the propshaft i mount the plate with long screw and at the bootom of the centerhull i glued and screw it with flex glue. So you can adjust the high of the ski and as is has open side , as ist is not a closed wedge ski, the water can flow free, that helps cornering. Maybee for saw it can adjust with a 3. channel servo to set a better ridding angle and propeller deep.

With re curved bottom i think Andy tought like the crapshooter has , that let the airflow slow down and suck the rear down with a slightly force so the back will jump less. But better with airtraps closing the channel left and right of the ski with rear sponson like the crapshooter had.

http://www.racecar-engineering.com/technology-explained/diffusers-engineering-basics-aerodynamics/

Happy Amps Christian
 
Last edited by a moderator:
Mike Betke said:
Andy Brown said:
The ski will work on all boats to a certain extent. But it's not simply plug and play to have it work well. The ski will have to be adjusted to work on the boat or the boat to work with ski. Or both.

The ski goes way back in r/c boat history. Marty Davis Crapshooters of the late 1970's used a ski.

Back in the day, my wife, Donna raced a K&B powered M.D. Crapshooter .21. It easily pulled a 1455 with an 8" pipe on 40%.

A couple of years later (1987) Donna won the Orlando Winternats with a .21 Mongoose that also used a ski against a field of 35 boats. Most of which were two rear sponson boats.

That Mongoose also used a .150" flex shaft that ran in an "S" bend tube. Jim Fetters and Ed Hugey were using and promoting the S bend Flex shaft system back in the early 1970's. Maybe even before that.

The bottom of the Mongoose tub was also Flat. The fast guys of that era, told me that would not work. They were all using recurved bottoms on the tubs.

I continued with Flat bottoms until 1996. The Eagle SG design used the recurve bottom and continues to present. I think current Crapshooters and Roadrunners are using flat bottoms along with others.

Both bottoms have benefits, but my 40 years of r/c boating experience says the recurve bottom is best for rough water racing conditions.

I forgot to mention. The 1996 Eagle SG was a two rear sponson boat. We put a ski and no rear sponsons on the SG in 1998 to help engines that had launching problems. The single engine SGX boat regained the two rear sponsons along with the ski. That set up set provided the best handling in all conditions. It set many records and won countless major races. The Twin SGX boats used a ski on each shaft and no rear sponsons.

In recent years we have set up the SGX with just two rear sponsons. That set up also works well with the correct power plant.

The red 1986 Mongoose pictured below also used the ski along with two rear sponsons.
Click to expand...
Thats some good info there Andy. I have found the same results playing with the recurve bottom in regards handling in race conditions.I'm finally starting to play around with a combination ski and rear sponson on the back. First test went very well.
Back in the 80's when we had hard shaft boats, Dad and I were putting a ski on, but we didn't know what we were doing in regards to helping the boat pull prop. We were just trying to keep the hard shaft tube from coming loose due to the vibration. Now we know why we were pulling big props back then.
Click to expand...
. A lot of the reason you were pulling a lot of prop with the hard shaft is the shaft angle you had with that setup.
 
Jeff Lutz said:
Mike Betke said:
Andy Brown said:
The ski will work on all boats to a certain extent. But it's not simply plug and play to have it work well. The ski will have to be adjusted to work on the boat or the boat to work with ski. Or both.

The ski goes way back in r/c boat history. Marty Davis Crapshooters of the late 1970's used a ski.

Back in the day, my wife, Donna raced a K&B powered M.D. Crapshooter .21. It easily pulled a 1455 with an 8" pipe on 40%.

A couple of years later (1987) Donna won the Orlando Winternats with a .21 Mongoose that also used a ski against a field of 35 boats. Most of which were two rear sponson boats.

That Mongoose also used a .150" flex shaft that ran in an "S" bend tube. Jim Fetters and Ed Hugey were using and promoting the S bend Flex shaft system back in the early 1970's. Maybe even before that.

The bottom of the Mongoose tub was also Flat. The fast guys of that era, told me that would not work. They were all using recurved bottoms on the tubs.

I continued with Flat bottoms until 1996. The Eagle SG design used the recurve bottom and continues to present. I think current Crapshooters and Roadrunners are using flat bottoms along with others.

Both bottoms have benefits, but my 40 years of r/c boating experience says the recurve bottom is best for rough water racing conditions.

I forgot to mention. The 1996 Eagle SG was a two rear sponson boat. We put a ski and no rear sponsons on the SG in 1998 to help engines that had launching problems. The single engine SGX boat regained the two rear sponsons along with the ski. That set up set provided the best handling in all conditions. It set many records and won countless major races. The Twin SGX boats used a ski on each shaft and no rear sponsons.

In recent years we have set up the SGX with just two rear sponsons. That set up also works well with the correct power plant.

The red 1986 Mongoose pictured below also used the ski along with two rear sponsons.
Click to expand...
Thats some good info there Andy. I have found the same results playing with the recurve bottom in regards handling in race conditions.I'm finally starting to play around with a combination ski and rear sponson on the back. First test went very well.
Back in the 80's when we had hard shaft boats, Dad and I were putting a ski on, but we didn't know what we were doing in regards to helping the boat pull prop. We were just trying to keep the hard shaft tube from coming loose due to the vibration. Now we know why we were pulling big props back then.
Click to expand...
. A lot of the reason you were pulling a lot of prop with the hard shaft is the shaft angle you had with that setup.
Click to expand...
That is correct Jeff. Donna's solid shaft .21 Crapshooter probably had 6 degrees of shaft angle which coupled with high front sponson AOA makes pulling big 1455 props easy. Donna's Mongoose .21 had about 2 degrees of shaft angle, lower AOA on the front sponsons and ran a 1450 prop.
 
Andy Brown said:
The ski will work on all boats to a certain extent. But it's not simply plug and play to have it work well. The ski will have to be adjusted to work on the boat or the boat to work with ski. Or both.

The ski goes way back in r/c boat history. Marty Davis Crapshooters of the late 1970's used a ski.

Back in the day, my wife, Donna raced a K&B powered M.D. Crapshooter .21. It easily pulled a 1455 with an 8" pipe on 40%.

A couple of years later (1987) Donna won the Orlando Winternats with a .21 Mongoose that also used a ski against a field of 35 boats. Most of which were two rear sponson boats.

That Mongoose also used a .150" flex shaft that ran in an "S" bend tube. Jim Fetters and Ed Hugey were using and promoting the S bend Flex shaft system back in the early 1970's. Maybe even before that.

The bottom of the Mongoose tub was also Flat. The fast guys of that era, told me that would not work. They were all using recurved bottoms on the tubs.

I continued with Flat bottoms until 1996. The Eagle SG design used the recurve bottom and continues to present. I think current Crapshooters and Roadrunners are using flat bottoms along with others.

Both bottoms have benefits, but my 40 years of r/c boating experience says the recurve bottom is best for rough water racing conditions.

I forgot to mention. The 1996 Eagle SG was a two rear sponson boat. We put a ski and no rear sponsons on the SG in 1998 to help engines that had launching problems. The single engine SGX boat regained the two rear sponsons along with the ski. That set up set provided the best handling in all conditions. It set many records and won countless major races. The Twin SGX boats used a ski on each shaft and no rear sponsons.

In recent years we have set up the SGX with just two rear sponsons. That set up also works well with the correct power plant.

The red 1986 Mongoose pictured below also used the ski along with two rear sponsons.
Click to expand...
Thanks for all that info, Andy...sure helped this 'catch up' guy!
default_smile.png
 

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