i was thinking

[Kelly Miller]

I would think that the width of the sponson and the deadrise would all have to take into account of course the weight of the boat and how much lift from air and resistance from wet surface, of course a deadrise would have a progressive amount of resistance in 2 ways, side and forward versus a 0 deadrise sponson being foward. I hope I made sense......there is only one thing that kept me out of college and that was High School...... fasinating information about all of the different results....what I see is it seems to be finding that perfect balance between all out speed for SAW and stability and handeling for heat racing. I seem to remember being told that my RoadRunner was not a SAW boat before I bought it......which told me some speed was taken out to enhance handeling. just my thoughts.

I got my boat straightened out , pulling to the inside, by sparpening fin, rudder and propeller and I dropped my left front a 1/16" at 6". putting the boat on a setup table often is critical. 1\16 makes all the difference in the world.

Saw some other things talked about here that certainly make me want to try some other things......great input.

Thanks keep it coming

 

[Jeff Lutz]

Marty, I'm glad to see you give some reasoning behind running high dihedral sponsons for straightline, I know what aggravated Don- Flat sponsons run on top of the water cleaner... You would have been better off taking all your trip chine out the side and keeping your dihedral low as possible on the bottom for straightline. This would have done 2 things- keep water from trailing up the side of the sponson resulting in a cleaner "get away" from the water while going straight, and then when you turn, the sponson would have dug slightly allowing you to turn better. For heat racing- dihedral with your 2 front sponsons pushed together forms a "deep vee" which helps it settle and absorb rough water conditions better. Some people think dihedral lets air under the sponson in rough water, making them run looser- they are in left field. Don Pinckert always said "air is cheaper than water" boy is he right, the reaction of the sponson angle on the water is everything compared to the air under the sponson. Of course dihedral, planing surface, and angle of attack all have to work together. I do agree in having more dihedral in the left then in the right, but as far as the sponson settling- a little bit of dihedral allows water to break under the sponson, the reaction of the water on the angle lifts the sponson, too much dihedral could possibly make it go the other way, but it would take a bunch. On the original roadrunners people were snap rolling them, (until they oversized the turn fins tremendously) and if they would have put a little dihedral in the left sponson they could have keep the smaller turn fin and not snap rolled. Don Ferrette -for your information- the tow in on front sponsons was not originally for countering prop walk, it was to keep average builders from towing the back of the sponsons in which would build water and cause drag. Jeff Lutz

 

[John Finch]

Good input Jeff. Have you tried ride pads under the sponsons like Andy uses. Any comments on those?

 

[Don Ferrette]

Don Ferrette -for your information- the tow in on front sponsons was not originally for countering prop walk, it was to keep average builders from towing the back of the sponsons in which would build water and cause drag. Jeff Lutz

Jeff Lutz- for your information- I didn't say that, John did, see post #73 & #75 again. And BTW- equal toe in on both front sponsons was done by at least one well known builder to make the boats track better with less of a tendency to "hunt" in the straights, this came right from the source.

 

[John Finch]

Toe in on the right sponson was used by SOMEONE to counter propwalk. Still being used. Problem is the boat crabs down the straights because the turn fin moves the front of the boat to the left and the prop drags the transom to the left, so if you exit buoy 6 in lane one you end up in lane 6 at buoy 1. Make sense?

 

[Jeff Lutz]

Good input Jeff. Have you tried ride pads under the sponsons like Andy uses. Any comments on those?

John, Yes, I'm running them now. The first time I seen them was on a picture of Ben Beard's F hydro from about 30 years ago. I asked my Dad about them on the boat in the picture about 21 years ago, his take on them then was the same as mine now. In good water with light sponson touches, you have less planing surface for less drag and reaction off the water, and in some cases you can get away with less dihedral using the pad in rough water. Although we are not talking about anything significant. Don, no offense I was just telling you the original reason for tow in. When everything is right, everything should be straight squared and centered. J Lutz

 

[Don Ferrette]

Don, no offense I was just telling you the original reason for tow in. When everything is right, everything should be straight squared and centered. J Lutz

None taken my friend. Let's keep this puppy rollin'.

 

[John Finch]

Jeff,

I am presently running a boat that has two ride pads where one is forward of the other. The outside pad is actually the one that touches the table. The inside pad is 1/16th off the table and more forward on the sponson. In the calm water it's a lot of drag. My 80 engine is ok with it but my 67 doesn't like it. At slow speed it is a lot of drag for the 67. In rough water I feel like there is more stability as there are two ponts of contact a little forward and back from each other and side to side they are separated as well. When we race, the water is always rough, so that's why I'm playing with trying to get more stability to handle the speeds we are running. I have a set of regular 3 degree diehedral sponsons I pop off and on the boat as well to compare. The 67 likes the normal sponsons better, but in the rough water the boat does get looser than I like. I also tried moving the ride surfaces forward and back to put more weight on the sponsons or take it off. I even spaced one sponson to ride at a different distance from the cg than the other, just because someone said that it was a no no. Guess what.......It works fine.

 

[Marty Davis]

Marty, I'm glad to see you give some reasoning behind running high dihedral sponsons for straightline, I know what aggravated Don- Flat sponsons run on top of the water cleaner... You would have been better off taking all your trip chine out the side and keeping your dihedral low as possible on the bottom for straightline. This would have done 2 things- keep water from trailing up the side of the sponson resulting in a cleaner "get away" from the water while going straight, and then when you turn, the sponson would have dug slightly allowing you to turn better. For heat racing- dihedral with your 2 front sponsons pushed together forms a "deep vee" which helps it settle and absorb rough water conditions better. Some people think dihedral lets air under the sponson in rough water, making them run looser- they are in left field. Don Pinckert always said "air is cheaper than water" boy is he right, the reaction of the sponson angle on the water is everything compared to the air under the sponson. Of course dihedral, planing surface, and angle of attack all have to work together. I do agree in having more dihedral in the left then in the right, but as far as the sponson settling- a little bit of dihedral allows water to break under the sponson, the reaction of the water on the angle lifts the sponson, too much dihedral could possibly make it go the other way, but it would take a bunch. On the original roadrunners people were snap rolling them, (until they oversized the turn fins tremendously) and if they would have put a little dihedral in the left sponson they could have keep the smaller turn fin and not snap rolled. Don Ferrette -for your information- the tow in on front sponsons was not originally for countering prop walk, it was to keep average builders from towing the back of the sponsons in which would build water and cause drag. Jeff Lutz

Jeff:

I agree with you analysis. I indicated that MANY years ago we ran high dihedral sponsons for SAW. I can see that SAW has evolved much since that time and people are running amazing speeds. I don't do SAW and haven't for many years. The only way that I have run SAW is as part of the Internats Trophy Trials. I did participate in a SAW at the Nats after the day was over and set a record for Sport 40 during that impromptu record trial. SO, my modern day experience with SAW is much limited.

I also agree with you about a very hard chine helping you turn. If you get the shine to high on a heat race boat, it will dart. Stu and I found that on the 67 boat that I ran for him several years ago. We softened the chine a little and the dart went away.

I also agree with you about running flat sponsons and fine tuning the attack angle. That has been my approach for many years. I do run 1 degree dihedral on the left sponson.

little toe-in on the right front sponson had been the norm for a lot of boats for the past many years. On my own boats I never run any toe in on the left sponson and less than 1/32" on the right. I just want there to be the SLIGHTEST amount of toe-in because I found that a boat that had any toe-out handled terrible and ran much slower.

Looks like I agree with all your points.....

There was a reply in this thread talking about the Boss Boat that Steve and Jack O'Donnell ran in Indy many years ago. It was an awesome boat and had some interesting characteristics in it. One thing was 2 strips on the bottom of the front sponsons with a gap between the strips as an air trap. What do you think of that approach? The guy that I sold Crapshooter to (Gregg Huey) started building sponsons with that approach shortly after I sold the company to him. I can see that using this approach would tend to allow the sponson to reduce the surface area in contact with the water while also making it vent the air immediatly if the sponson lifted at all. Seems like a good approach. An approach that I never experimented much with. Maybe I will revisit that.

Marty Davis

 

[impba3548]

This topic has made for some interesting reading thats for sure!! I dont really qualify to add something to this post, however I have a gas rigger that pulls badly to the right. I tried the tow in on the right sponson with limited success, also turn fin tow in. I had as much as 8 degrees of left in the strut to make it run straight! Since then I have offset the sponsons an inch to the left (right one in 1/2" left out 1/2") straightened the strut to Zero, and the boat runs relatively straight with zero left trim in the rudder. My theory is that this offset produces little if any extra drag. I also offset the drive 5/16" to the right with little effect as well.

The gassers turn lower rpm, bigger diameter, higher pitch props etc. all of which makes the right pull problem worse. Does anyone have any input on this sponson offset as to whether it produces more drag, as some of the other solutions can?

The props are sharp but not to the point of bloodletting!

thanks

mike sr

 

[ek kustomz]

This topic has made for some interesting reading thats for sure!! I dont really qualify to add something to this post, however I have a gas rigger that pulls badly to the right. I tried the tow in on the right sponson with limited success, also turn fin tow in. I had as much as 8 degrees of left in the strut to make it run straight! Since then I have offset the sponsons an inch to the left (right one in 1/2" left out 1/2") straightened the strut to Zero, and the boat runs relatively straight with zero left trim in the rudder. My theory is that this offset produces little if any extra drag. I also offset the drive 5/16" to the right with little effect as well.The gassers turn lower rpm, bigger diameter, higher pitch props etc. all of which makes the right pull problem worse. Does anyone have any input on this sponson offset as to whether it produces more drag, as some of the other solutions can?

The props are sharp but not to the point of bloodletting!

thanks

mike sr

I could be wrong but from what I have been studying and reading its not that the off-set creats more drag but it increases the leverage on the left sponson therefore it tends to pull the boat left. Just like if you were to move a cg front to back. It changes the pivot point of the boat and makes it pull left. It may take a few times to adjust it to compensate for prop-walk due to having to find what works for a certain prop.

Hope this Helps,

Zach

 

[impba3548]

My hopes were to get the left leverage without adding drag, I guess it worked as yesterday the boat ran straight and just a touch over 80 on a 91 degree day, so I guess it works!! The boat looks kind of funny though, but the numbers are what counts.......

mike sr

 

[ek kustomz]

My hopes were to get the left leverage without adding drag, I guess it worked as yesterday the boat ran straight and just a touch over 80 on a 91 degree day, so I guess it works!! The boat looks kind of funny though, but the numbers are what counts.......
mike sr

Numbers are what counts. I think I have only one boat with no offset in it. I'm glad it worked for you. No extra drag just a longer lever.

Zach

 

[Joe Warren]

This topic has made for some interesting reading thats for sure!! I dont really qualify to add something to this post, however I have a gas rigger that pulls badly to the right. I tried the tow in on the right sponson with limited success, also turn fin tow in. I had as much as 8 degrees of left in the strut to make it run straight! Since then I have offset the sponsons an inch to the left (right one in 1/2" left out 1/2") straightened the strut to Zero, and the boat runs relatively straight with zero left trim in the rudder. My theory is that this offset produces little if any extra drag. I also offset the drive 5/16" to the right with little effect as well.The gassers turn lower rpm, bigger diameter, higher pitch props etc. all of which makes the right pull problem worse. Does anyone have any input on this sponson offset as to whether it produces more drag, as some of the other solutions can?

The props are sharp but not to the point of bloodletting!

thanks

mike sr

Mike todays tuning tips are to decrease the angle of attack on the left front sponson if the boat is pulling to the right. You can do this by adding shims to the rear boom tube area. I have always ran the right front sponson attack angle higher than the left front. AS for Sponson Off set, Some boats have engine off set, Some Sponson & engine offset, But you are playing with the turn fin weight, & this effects the boat the most as for turning performance. NOW for my question, Some riggers have flat bottoms, Some 1/16 blow out Some 1/4 blow out, How does this effect the boat & If the boat has more or less blow out Does it work best with a netural running tub or a Negative angle tub. I have built & tuned many Riggers & have not seen any Rigger guru`s answer that question yet?

 

[John Finch]

What do you mean by blowout , Joe. The bottom having a small vee like on a mono or the curve upward towads the transom.

 

[Joe Warren]

What do you mean by blowout , Joe. The bottom having a small vee like on a mono or the curve upward towads the transom.

John The taper on the bottom of the tub from the front of the radio box to the transom. Allowing the air to vent out front under the boat.

 

[John Finch]

Joe, I played with that a lot three years ago. Seems like 1/4 inch works well. Less than that and you get either really fast or really stupid results and it is super crittical. I had a hull that every race weekend I took out some of the curve. The boat stayed the same till I got to somewhere about 1/8th of an inch or less. I can't remember exactly how far I went. I would have to look up my notes. The boat went really fast as air packed the transom and floated the boat. I went about a sixteehth less angle and the boat stuffed. Don Pinckert's ground effects boat works off the principal of controlling the air at the transom for a low drag air cushion ride. I was shooting for that type of arrangement. What I found was that the amount of air trapped at the transom is very crittical. Hair line between really fast and submarine. The only boats I have seen as of yet in my experience that work consistently well with a flat bottom are the heavy gas sport boats.

 

[Ray Sametz]

John, Thanks for sharing your ideas on " blow out ". Whats your thoughts on the nose of the tub, ie sharp wedge, rounded wedge or some type of bullet shape. Ray B) B)

 

[John Finch]

Sharp leading edges tend to hunt. More blunt is better. The curve on the bottom of the boat from the very nose to the engine is opposite what you might think. I once thought that having the centerline of the nose higher on the tub would cause blow off because more air would hit the bottom half of the boat than the top half. Just the opposite. More curve at the bottom half of the hull helps to suck the bow down because of the negative air pressure caused by the curve.

 

[Ray Sametz]

It's funny John, my best heat racing boat is a 90 Mongoose. Very reliable, drives were you put it, very predictable. What are it's features, nose point above centerline of tub, flattened angle back. No toe in on sponsons. Turn fin very flexable, it takes a set an corners great, also parallel to tub. Offset drive line, it tracks straight, no negative left rudder. Rear sponsons under the tub. To bad back in those days the 90 motors didn't make the power they do today, maybe they would not have dissappeared so quick. I will point out I also owned a 20 & 40 size and they were a handful to heat race. Ray B) B)