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riggerman

Ride pad shape ?

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Hi all  every ride pad side profile i have seen has a gentle  curve from the rear of the pad that gently curves into the bottom of the tunnel.  Has anyone  tried a wedge shaped profile  for a ride pad ? Regards Andris Golts.

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The wedge shaped sponson doesn't provide the support needed to the front of the hull and will allow the forks to go under the water and turn your boat into a submarine when you slow down or turn. A sponson can have a series of wedges (shingles) from front to rear and that kind of works but that arrangement gets complicated and tends to be very hooky and unpredictable in the turns due to a variety of hydrodynamic downfalls. I tried all that years ago and it produced nothing positive. The best arrangement for an outboard tunnel (to this point at least) has been the smooth radial bottom design.  It's a trade off just like everything else on a tunnel boat but is works well. That flat plane technology that is the rave these days works great on a hydro but it is not the direction to go for a tunnel boat in my opinion.

There are some saying that if done right it will work and all but nobody has produced a shingled bottom outboard tunnel boat that has impressed me yet. If you are truly thinking of designing something that will be competitive with today's designs, don't get far off the path of what is working now and try to make improvements from there. I will tell you that improvements will be small but they are there to find.  I have just released one of my newest designs " the Taboo" and it does not have wedges, steps or shingles on the sponsons and it has very nice characteristics at more than acceptable speeds.

For example, the newest production design in my shop (the boat that will one day replace the recently released Taboo) does not have stepped sponsons on it either. When I release a model to production I already have the next design ready to go but someone will have to build something to outperform the Taboo before that design leaves here.

My point is, wedges or steps on your sponsons are probably not going to produce a truly competitive round track outboard tunnel boat.

-Carl

 

 

Edited by Carl Van Houten

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I have done some testing on this years ago.. the short answer is well. kind of. You want the boat to stay put on the water BUT.. not get drug under.

having a "break" in the riding surface (not a vent or a step). CAN work but its not a great solution. When turning you have to maintain limited contact. (its about that maintain deal!)

Grim

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Grim,

Limited contact is always a good thing. The old Twister Craft was the closest thing to a stepped bottom outboard tunnel boat working that I have ever seen. They were built super lite weight and would jump off the corners like it was shot out of a freaking cannon and was probably the fastest outboard tunnel "that used steps" that I have ever seen ( for the time period anyway ) but it got around the turns by a series of quazi controlled hooks.  It took someone like Karl Strum and Dusty Tranum that could drive the prop off of anything to actually make that crazy thing get around the track without running over everything in its path. Even as good of a driver as these guys were it was still a hand full driving one.  

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On 1/28/2019 at 6:40 PM, riggerman said:

Hi all  every ride pad side profile i have seen has a gentle  curve from the rear of the pad that gently curves into the bottom of the tunnel.  Has anyone  tried a wedge shaped profile  for a ride pad ? Regards Andris Golts.

Andris,

Can you clarify your question?

Thanks,

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Andris,

Another consideration is the tunnel roof to the ride pad. The tunnel must run positive or act positive to the flat section of the sponson.. more or less regardless of how long the flat section is.

Forward of that point the critical part is stability in cornering. If you have a sponson design that does not "set" or balance the drag, the boat will hook or drift. Carls designs are top of the mark here and so he is best to chime in.

 

Grim

 

 

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Thanks for the compliment Grim. As much time as I spend screwing around with tunnel boats they should run a lot better than they do :D I just  try to make my tunnels boats do want I want them to but it's a lot like trying to teach the worst kid you can think of to behave at the dinner table. It can take a while and make you want to go out in the back yard and beat on a tree...LOL 

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Hi Carl thanks for your input to clarify my original  ?i  am asking about the ride pads side profile the one's that  are installed on both port and starboard inside  sponsons  approaching the bow area. As i mentioned in my original post  that all ride pads i have ever installed on the tunnels i have built looking from the side the rear of the ride pad sits about a 1/8'' of an inch bellow the sponson bottom and gently curves into the tunnel bottom. I was just asking if anyone has just tried a wedge shape side profile instead of the standard curved side profile . Sorry for the confusion. Regards Andris Golts.

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Okay, now I see. Well those are called many different names and that has caused a lot of confusion in the past. I have just recently seen a boat that had wedges. I am not sure how well that hull actually works. I personally do not use wedges on any of my models. I like the curved type as they produce the best results for my type hulls.  I call them A.S.P's (Anti Spin Pads) but others call them different names depending on who you talk to. They were first used on the XT years ago and they made that boat unbeatable at that time. They are still used on the modern style tunnel boats and serve to add additional displacement and stop the hull from taking too much "bite" in the turns once the boat has reached its full set.  They have to be tuned to each hull depending on its particular needs. You only want them large enough to do the job. Any more would just add unnecessary drag. 

Hope this helps,

-Carl

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The Nemesis had just such a stumble block. (two flat planes) One at 3deg or so positive from the tunnel and the forward one making up the depth of the pad to the length.. (I can not remember the length).

Grim

 

 

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Somebody... mike z.. lol... or maybe dunny at the time... had given me a percentage measurement etc... that  the stumble blocks needed to be installed vs the OAL hull length and whatnot.... it really is... a test game...I did better on curved also though...    the XTR when it came out rocked.... and.. maybe somebody can pic the turn spoon from the back.... as... it has built in designed "splash kick"  for lack of an engineers terms that imo stops the water from climbing the sponson dihedral angle and sucking the sponson down in the turn...(hook)  added flotation....maybe...  .. now... I applied... this same theory to a dunlap 30 hull ( modified boat)… that quirked on maiden....a lot... hook... spin... and a simple 1/4 x1/4 triangle stock glued to the turn spoon ( see XTR boat)… solved it instantly... it prevented the water from climbing the sponson angle and pulling it down once I set for the turn...  anyway...im out of the tunnel loop, I do own a newer style what im calling a wedge style hull...  and the rowing after them will continue.... keep the learning alive here... thx.... mike

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