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rear sponsons


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#1 jamie anderson

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Posted 08 August 2018 - 11:22 PM

I would like to know why some riggers have rear sponsons and some don't .

what are the benefits to having them or not having them.





#2 gil sonsino

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Posted 09 August 2018 - 01:55 PM

There are pros and cons in both types of riggers.Rear sponsons contribute to stabilize the rear of the boat in some water conditions but also produce some drag too. I have tested  from the early SG's with rear sponsons  then they changed to the rear central one then to three rear sponsons and now to only two and all boats were great runners.The Jae serie has just the central rear called "ski" and since they enlogated tubs and raise the witdh between sponsons they became tremendous contenders.There so many factors like afterplane,COG,flat or dihedral sponson's bottoms,aerodinamics,type of propellor, etc that its quite difficult to answer your question with few assertives.Lets the experts chime in. Gill





#3 Mike Hughes

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Posted 09 August 2018 - 07:03 PM

Well most of your modern day rigger are running some kind of lifting device for the rear end. IE sponson, ski, wing, or any combination of all of them. There were some older style riggers in the early 90s that did not run them. The all do the same thing. Lift the rear end of the boat and keep it planning. Makes for a more consistant ride. You can now flatten out the strut so that you are thrusting only to push the boat forward. In the past we used to run the prop at an agle to lift the rear end. 

Just a few reasons. 

Mike 



#4 jamie anderson

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Posted 10 August 2018 - 01:54 AM

thanks very much for your input. does having rear sponsons make the boat corner better? 



#5 Carl Van Houten

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Posted 10 August 2018 - 06:03 PM

Try racing an outboard hydro without them...the first time that rear end drops in a hole she pops off the water with no warning what so ever.  



#6 Michael Costanzo

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Posted 11 August 2018 - 07:55 AM

thanks very much for your input. does having rear sponsons make the boat corner better? 

it makes the boat have something to ride on in the corners and make the hull more stable in rougher water.



#7 BobBonahoom

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Posted 14 August 2018 - 07:14 PM

Here is something that might be of interest in this topic.  I have a 45 Roadrunner that always hopped at the strut and lost speed in the straights because of the hopping.  I tried all kinds of strut angles, props, strut depths and front sponson angles and could not get it to ride flat without the hop-hop-hop.  This version or Roadrunner does not have a flat bottom.  Instead the bottom begins to rise a bit from just behind the engine to the transom. 

 

I was looking at my JAE boats hanging in the garage and decided to try something.  I removed the Roadrunner's rear sponsons and made a 2" wide ski with a depth equal to the specified strut depth for the Roadrunner.  I painted the ski area black and went to the pond.  The boat ran very well with no hop! The other thing that I found was that I could launch much bigger props than I had ever launched before.  The bigger props were not always faster, but they launched and ran allowing me to optimize for the best prop.  I am running a CMB 45 VAC in this boat with a Bouchie pipe.  I am not sure what this means in general, but for my particular 45 Roadrunner the wide ski seems to have transformed it into a better boat.  We have a Crapshooter 45 that runs great with rear sponsons...so who knows?  Just thought you might be interested in this experiment.

 

 

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#8 David Murany

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Posted 14 August 2018 - 07:58 PM

Here is something that might be of interest in this topic.  I have a 45 Roadrunner that always hopped at the strut and lost speed in the straights because of the hopping.  I tried all kinds of strut angles, props, strut depths and front sponson angles and could not get it to ride flat without the hop-hop-hop.  This version or Roadrunner does not have a flat bottom.  Instead the bottom begins to rise a bit from just behind the engine to the transom. 
 
I was looking at my JAE boats hanging in the garage and decided to try something.  I removed the Roadrunner's rear sponsons and made a 2" wide ski with a depth equal to the specified strut depth for the Roadrunner.  I painted the ski area black and went to the pond.  The boat ran very well with no hop! The other thing that I found was that I could launch much bigger props than I had ever launched before.  The bigger props were not always faster, but they launched and ran allowing me to optimize for the best prop.  I am running a CMB 45 VAC in this boat with a Bouchie pipe.  I am not sure what this means in general, but for my particular 45 Roadrunner the wide ski seems to have transformed it into a better boat.  We have a Crapshooter 45 that runs great with rear sponsons...so who knows?  Just thought you might be interested in this experiment.
 
 


Bob,

It sounds like you had too much AOA on the rears of that boat. They should be 1.7 to 2 degrees on the bottom. If you ever go back to them make a jig out of 1/8" plywood with a small piece of 1/8" plywood on each end 3" apart and use that to put the sponsons on.

If you have any Roadrunner setup questions let me know. We have 6 of them.

Dave

#9 BobBonahoom

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Posted 15 August 2018 - 03:19 PM

Dave,

 

I forgot to mention it, but early on I removed the sponsons and re-applied them using the gauge you are describing but I still had the hop problem.  Interestingly I told Ralph about it and he mentioned that another guy had the same issue and they finally traced it to a bad flex shaft.  By the time I heard that, I had already put the ski on the boat which seems to have solved the problem.