rear sponsons on an outrigger- where & why

[Don Ferrette]

Since the sponson deadrise thread turned out to be a great topic of info I'd like to generate another hopefully as strong. Rear sponsons on an outrigger where & why. There are many variations - on the sides of the tub, under the tub, flush with the transom, extended past the transom, running them even with the strut or raised up. I'd like to start by asking about people's preference on rear sponson depth, pros & cons of raised vs. even with the strut. Let's hear some thoughts on this ....... B)

 

[ek kustomz]

Don I have absolutely no idea. But I would like to know as well and I found the other thread very informative. You think they could archive that??

 

[Ray Sametz]

Old school and my way, rear sponsons set at center line of prop shaft on flat bottom strut @ 0 degrees. MHO better launchablity with bigger wheels. Round bottom strut, flush with bottom @ 0 degrees. Hop and ride can be adjusted now with tuning prop. I'm talking riggers only. h34r: h34r: B)

 

[Preston_Hall]

This question comes from a "World Racer"?

 

[John Finch]

That's MR. World Racer to you buddy.

 

[John Finch]

If they have too much angle of attack: the back of the boat will hop. Marty told me that one at the 97 nats.

If they are not on the boat the boat goes faster, but the boat doesn't handle well.

If they are painted by Don: they look better.

If there is no non trip on the left outside sponson the boat can roll over in the corners.

They help to float the boat while it is waiting on the retrieve boat.

 

[Don Ferrette]

This question comes from a "World Racer"?

LMAO! A question to generate a good topic of discussion, just like we had in the deadrise thread. Everyone has their own preferences so let's hear why. Be a part of it or be a smart azz, I don't care either way.

 

[Ray Sametz]

From a club racer to the boater, John I wish I knew what you forgot. Helps boat float while taking walk of shame. :lol: :lol: :lol: :lol:

 

[Preston_Hall]

If they have too much angle of attack: the back of the boat will hop. Marty told me that one at the 97 nats.If they are not on the boat the boat goes faster, but the boat doesn't handle well.

If they are painted by Don: they look better.

If there is no non trip on the left outside sponson the boat can roll over in the corners.

They help to float the boat while it is waiting on the retrieve boat.

You forgot that they are also right and left handed launch handles.

 

[Marty Davis]

Since the sponson deadrise thread turned out to be a great topic of info I'd like to generate another hopefully as strong. Rear sponsons on an outrigger where & why. There are many variations - on the sides of the tub, under the tub, flush with the transom, extended past the transom, running them even with the strut or raised up. I'd like to start by asking about people's preference on rear sponson depth, pros & cons of raised vs. even with the strut. Let's hear some thoughts on this ....... B)

Don:

My knowlege of rear sponson systems is somewhat simple. I have had a lot of success with a specific type and setup of rears and do not know a lot about the other approaches.

My system involves rear sponsons which ONLY act to stabilize the boat in the turns, at launch and at mill speeds. The rears MUST be at an attack angle that is less than the fronts in order for the rear of the boat to not overwhelm the front. If you have an attack angle on the rears which is much more than 1.5 degrees you will get a "high frequency hop". You will have to look at your boat VERY carefully to see it. It steals a ton of speed if it is present. I run 1.5 degrees on my 20 boat and a little less on 40 boats and a little less on larger (1 degree +/-). As john Finch stated the chine must be gradual enough that it does not catch the water in the turn, but allows the boat to easily turn the rear end without digging.

As for depth of rears, I like to use the approach where the bottom of the rears are even with the bottom of the strut. Both the strut and rears are 1/8" shallower than the front sponsons with the belly of the center section level.

As you know, I used to own Crapshooter Boats back in the 70's and 80's and we ran a solid shaft with a wide strut log (1/2" - 5/8" wide). That also was responsible for keeping the boat up in the rear, but we still had to run rear sponsons.

I would also direct this discussion to Stu Barr and Andy Brown as both have a system that is different than mine. I know that Stu uses rears that are substantially shallower than the bottom of the strut. I ran one of his 67 boats for a season and loved the way it handled. There must be some setting that he uses that also works super well. Andy had used MANY different setups in the rear including using air instead of mechanical contact, one center shoe, contact rears, etc.

Marty Davis

 

[John Finch]

I experimented with Andy's design a lot the past few years. The center shoe keeps the boat up in the corners but gives no side to side flutter stability. The center shoe deeper than the two outside ones lets the boat run a bit loose (lets the front sponsons free up a bit). The outside deeper than the center shoe gives a more planted feel to the boat. All three same depth.....didn't see much difference than with deeper outside sponsons. I did take out the center shoe and the boat did not launch as easily. I then added material to the bottom of the hull at the rear 1/3rd of the hull to pack more air under the boat. I did this both with and without the center shoe. There came a point almost flat with the whole bottom of the hull that the boat was extremely fast and smooth. Faster than all the other setups using the mod bottom and two outside sponsons. Then I experimented too far on getting the tub almost entirely flat on the bottom and the boat stuffed one time on me. I then rolled the back 5 inches back up like the original crapshooter and the boat hoped like a bunny rabbit at full speed. Don remembers that experiment. I laugh every time I think about it. I then went back to the original 3 sponsons but moved the outside sponsons out to the sides of the boat using a 1/8 inch piece of plywood glued to the bottom of the hull extending past the sides and glued the sponsons to that board. Won the 67 class with it at the last race, but the boat fluttered down the front straight one time and crashed. I now have rears mounted to the side of the boat like a roadrunner style setup and the rears go all the way back to the prop. Gonna try that setup Saturday.

 

[Chris Wood]

My system involves rear sponsons which ONLY act to stabilize the boat in the turns, at launch and at mill speeds. The rears MUST be at an attack angle that is less than the fronts in order for the rear of the boat to not overwhelm the front. If you have an attack angle on the rears which is much more than 1.5 degrees you will get a "high frequency hop". You will have to look at your boat VERY carefully to see it. It steals a ton of speed if it is present. I run 1.5 degrees on my 20 boat and a little less on 40 boats and a little less on larger (1 degree +/-). As john Finch stated the chine must be gradual enough that it does not catch the water in the turn, but allows the boat to easily turn the rear end without digging

marty,

funny you mention the 1.5 degrees.. my boats are slightly more but i don't see the HOP.. i also set the rears close to what you do.

chris

 

[Don Ferrette]

As for depth of rears, I like to use the approach where the bottom of the rears are even with the bottom of the strut. Both the strut and rears are 1/8" shallower than the front sponsons with the belly of the center section level.

So with this setup are your rear sponsons flush with the transom or do they extend past like say a Roadrunner? B)

 

[Marty Davis]

As for depth of rears, I like to use the approach where the bottom of the rears are even with the bottom of the strut. Both the strut and rears are 1/8" shallower than the front sponsons with the belly of the center section level.

So with this setup are your rear sponsons flush with the transom or do they extend past like say a Roadrunner? B)

Me rears extend well past the transom. That makes a long lever arm which helps in effectiveness.

Marty Davis

 

[Tofastformellow]

just a question from right field here ..more to challange the theory , nothing more

just a little like trim tabs on a strait bottom mono, if a rigger was built right would it be better to not have them at all ...??

i notice they dont do much if you keep the throttle nailed .. but they do help if you back off over rough water. But if your on a flying lap , and shooting for sub 1 min heat times ?? shouldnt you have it nailed all the way . hence the rear sponsons are just extra weight??

im noticeing on some aussie heat boats now , the rear sponsons have a traditional bottom shape , but the top shape similar to the top of the wing angle on a sgx..

have any people noticed this trend ?

when the rear sponsons rip/fall off my rigger , i really dont notice much difference at all?

but my boats are set up with a front bias , not setup as a tail draggers

arnt rear sponsons a little like having training wheels ?

Jase

 

[Don Ferrette]

arnt rear sponsons a little like having training wheels ?Jase

Actually think of them more as wheeliebars on a drag car. Without the rears if the boat gets loose in the front there is nothing to settle it back down. When we do record trials there are no rears (except generally for a center shoe) because you're by yourself & typically on glass smooth water. But if the boat gets out of shape at all then usually you are toast. :blink:

 

[John Finch]

So far everyone talks about using the rears only for cornering. They do keep you in the race in the straightaway too. For expample, if the front left sponson hits a wave and pops up in the air, the right rear sponson keeps the boat from getting out of shape. Just the right wheely bar in use for that scenario. I have found this to be true in heat racing conditions. I have found that just a 1/16th piece of plastic taped to the right rear shoe of a 1/8 scale boat was enough to push the left front sponson down onto the water in the straightaway, even though the rear shoes don't touch the water in the straightaway. Aerodynamics plays a big part too, and under a boat the air packs between the hull and the water. That's why some birds coast just a foot off the water for long distances. They are packing air between their wings and the water. The width of the boat hull is also a player for this reason. Note how a large sport gas hydro rides great without rear sponsons. They have wide hulls and pack air under the hull. The cg location is also a player there. Look at the outboard riggers with the engine mounted on the transom. They have large rear sponsons to support the weight at the transom and they work quite well. There are so many variables that the possibilites are endless.

 

[Tofastformellow]

wheelie bars on a boat .. Check .. ok :unsure:

so if you want to get rid of rear sponsons then you need a wider tub ??

what is faster in design and in the records around an oval .??

a three point hydro or a four point hydro ?

will it work to fit bigger winglets on the rear of the boat and smaller rear sponsons..

and how would a boat that looks like the rear of the team jags saw boat preform if it was reprofiled for heat racing ..

ie a little thicker(higher profile) in the tail.

the shape looks very fast , and its proven to be very fast in a strait line.. but if the rear was set to lift at the correct rate , wouldnt that do the job without rear sponsons... or i suppose at a compramise some really really thin rear sponsons. like 1/16th

what will riggers look like in 50 yrs time..?? will they still use rear sponsons or wil aero dynamics be more important than hydro dynamics for the future , and i suppose the end goal of running faster ...

i am asking all these dumb questions as i am busy building some electric test riggers ..

thankyou

for eg



Jason

 

[Mike Larson]

All my hulls have the even with the bottom of the strut theory goin on, relating to basic set up rules/instructions..... this post has already helped solve a quirk in one of my scratch built '40s and will go to test...... now, i've run offset rears on my ninja since day one.. ( scratchin my head on how to not allow the rudder to hit the rear on right) and, sustaining the question: does this allow the air to trap/escape at a parallelogram tangent vs straight out the rear, thus, going with the criss cross hull theory, relieve pressure unevenly on the left front? Reason and questioning behind my dumbly asking Gary P one day at a race where he lost his rgt rear sponson! ( fast boat, smart man) If, the rgt rear is as almost useless, needing possibly only the left to help turns, and at launch.... possibly a specialized built hull, didnt look so......

with the AOA of the rears important, the stated theory to be gained so far, then, is that "hop" is the indicator that the fronts and rears are working against each other aerodynamically, and a possible change is in order? do you, and can you without changing the depth "tune" as in shimming booms, the rears to what maximum angle before the effects are negative? generally said around 1.5,being normal, but, what, of larger angles, and the resulting effects at speed

How, then do men with the eagle style hulls, and non removable sticky sponsons adjust their ride?

A few more from left field, bear with me:

Has anyone tried offsetting depths right to left on the rears?

Why would not just a small airfoil design work for the rears on a saw boat, if just speed, and one launch were all that are needed? didnt hope to stomp on your post Don, the questions kinda pertain, my knowledge is small, just thinkin big..... mike

 

[John Finch]

Training wheels slow you down, but they keep you safe. How fast do you realllllly need to be to win?

Not very.