Air Trap Sponsons

[SayMikey]

Mark and I have had the shingles on my sport 21, Crapshooter 101 hydro and on SGX60 and my SST twin 90's. There was marked inprovement in the launch and getting up on step and the acceleration is greastly improved. The boats also seem to handle the rough water better.I will atest to Mark's statement on the fact that he did not borrowed the idea. His account is correct because I was at the same Nats, running partner, and we discussed the concept at length.

The tunnel spnsons have been around for a long time. The first that I saw was years ago at a race in New Orleans and the O'Donnell's had a baby blue hydro with the tunnels and many other innovative concepts in the boat. They ran a Picco that was air cooled.

Another amazing boat at that race was a black guy who came all the way from California and he had a bueatiful black twin that he would "rope" start.

I wonder how many folks have seen motors started with a free hand ROPE?

Gary:

His name was Gene Adams, and yes his boats were awesome!

Marty Davis

Those were the good ole days. It is amazing the improvements since that era in radios, servos, hull and material technologies. When we traveled we had to be SOOOOOO careful not to bump the rudder because it would strip the gears in the servo. Gary

I did see Scott Jones flip the flywheel on a 21 tunnel and start it, i got one to start one time but bet in a heat race situation id be 3 heats late...Mike

 

[Ray Sametz]

Well I have roped a boat or two. Not many and only when the belt had broke. I once started a motor with the broken belt. It is a lot like propping a airplane motor. I started flying airplanes before they had starters and never bought a starter until I got into boats in the early 80's.

Mark, I never even use a "Chicken stick". Remember the old springs, hook the prop, wind it backward and let her fly. Mike, D-1 director Randall Thomas starts his O/B by spinning the flywheel by hand. B) B)

 

[Mark Bullard]

Well I have roped a boat or two. Not many and only when the belt had broke. I once started a motor with the broken belt. It is a lot like propping a airplane motor. I started flying airplanes before they had starters and never bought a starter until I got into boats in the early 80's.

Mark, I never even use a "Chicken stick". Remember the old springs, hook the prop, wind it backward and let her fly. Mike, D-1 director Randall Thomas starts his O/B by spinning the flywheel by hand. B) B)

I never used a chicken stick either. Still have scars on my finger from cold weather backfires. Sixty size motors hurt the worst. On the little 049 the spring was about the only way of cranking them. They were very hard to get enough fuel in the cyclinder. On the bigger motors just put your finger over the carb and pull the prop thru a few times. Then connect the glow battery and slowly turn the prop thru holding the prop until you feel the motor bump. Then pull the motor thru and the motor would come to life every time.

 

[Niklas Edlund]

I think this guy from Poland roped his rigger at the recent NAVIGA worlds in Italy... Its no belt in the rigger anywho and he's just about to go out to the pontoon... The rigger was not too bad as you might think... LOL

 

[TomMoorehouse]

is the rudder being held on with a rubber band?

 

[Ray Sametz]

Maybe a twist tie from a loaf of bread.

 

[bzubee]

It looks like it is set up with the band to allow kick back if it hits anything. I like the kinks in the water lines and the radio box lid !

 

[Niklas Edlund]

is the rudder being held on with a rubber band?

Yes. But that is instead of the brass screw we use as a break-off pin.

Its lots of small details to make you feel all warm inside of that rigger...

But as earlier mentioned - dont laugh too high though - at least I was surprised about the performance... I have seen worse! LOL

 

[Ray Sametz]

is the rudder being held on with a rubber band?

Yes. But that is instead of the brass screw we use as a break-off pin.

Its lots of small details to make you feel all warm inside of that rigger...

But as earlier mentioned - dont laugh too high though - at least I was surprised about the performance... I have seen worse! LOL

Niklas, I've had my butt whiped by worse looking boats. Just pulling your leg.

 

[Niklas Edlund]

Ray: LOL

Leave room for the air trap sponson talkers now...

 

[Ray Sametz]

Tossing out a idea. Very rough sketch of sponson. Lighten and maybe add some downforce with less drag???? B)

 

[GiantScale13]

Take a look at this one.

http://www.shrani.si/f/2c/9e/FpIfdPF/sponsonbott2.jpg

 

[Andy Greene]

Tossing out a idea. Very rough sketch of sponson. Lighten and maybe add some downforce with less drag???? B)

I don't know how that would work but it would have to have some sort of step on the top side to produce the aerodynamic flow inside- simular to what's used on a F-1 car. There is an aerodynamic term for it that eludes me right now..... Long day at work.

Build it Ray, you never know-

Andy

 

[jetpack]

Laminar air flow tunnels?

NACA ducts perform well but not sure if this is the idea.

Picture the F1 car upside down for the sponson.

 

[Mark Bullard]

Tossing out a idea. Very rough sketch of sponson. Lighten and maybe add some downforce with less drag???? B)

Would be very easy to try. You never know what it might do. I don't think it would would cause downforce. But there again I don't know. A wind tunnel would help. I do know the pointed noses on the tips of sponsons are not good. You want a shape of roundness. Another thing is when designing a boat you want the bottom of the sponsons very close to where it will run and the top as flat as it can be. If you have the top flat and have to lower the AOA it will angle the top of the sponsons down at the nose. This will cause downforce. And if you have to go the other way when your top is flat and have to increase the AOA it will raise the nose of the sponsons and cause lift. So the top of the front sponsons needs to be kept as flat as possible. This will help the boat fly right.

 

[Ray Sametz]

Mark, Thanks for the reply, I should had emphasized very, very, rough sketch. The main point was the elliptical hole thru the sponson. Not even sure of the angle. B) B)

 

[Charles Perdue]

Hello Ray, at the least, you are thinking out of the box. Keep it up.

As for the wedge shaped sponson, SOS......Same Old Stuff......The wedge is one of the most unstable aerodynamic shapes there is. A brick has a more stable shape. A long round cylinder radiused on the end ....Hot dog shaped is a much more stable aerodynamic design....look at the design of most aircraft.

One of the few times that a wedge shape is used in aircraft is the design of the F 117 Stealth Fighter. It cannot maintain stable flight more than about 5 seconds without very serious computer assistance.

Charles

 

[John Finch]

Marty,

My 67 eagle has tunnels in the front sponsons. The boat rides very smooth, but not any faster than stock setup for heat racing. Record trials might be a different story as the ground effects and riding on air is faster as you know. My oval record boats don't have the tunnels, but the sponsons are wider than normal to trap air and float at speed while also giving more lift at slower speeds to get the boat up on the water with large props. I am using a bit of ground effects on my straightaway rigger for next spring using the narrower sponsons, so I can let you know how that works latter down the road.

On the other subject...............I was one of those start rope guys in the 60s. Funny how things come back around. I'm using the rope start again in 2008, only on a gas engine!!!!!!

 

[SayMikey]

Tossing out a idea. Very rough sketch of sponson. Lighten and maybe add some downforce with less drag???? B)

Ray all i can think about is taking gas out of a car,once you start a siphon<water sucking up the hole will it stop?

 

[John Finch]

OK

Charles,

Do the shingles need to be one right after the other to work on breaking up the water or can they be spaced far apart like the aeromarine cat hulls if your not looking for the air trap, just breaking the suction?