Monos built strickly for SAW?

[bzubee]

Same here terry you can sure pick up some good speed tips for heat racing and even play boating. Just by attending, watching and asking question at a records trial.

 

[John Finch]

You guys got me thinking now about a flat bottom mono like they use in the full size drag racing. If I cut the sides of my sport gas hydro, add some vee to the bottom, Remove the sponsons, cut the bow in at the sides, add a bit more vee up front. HUM <_< Yup, still having fun!

 

[Andy Brown]

You guys got me thinking now about a flat bottom mono like they use in the full size drag racing. If I cut the sides of my sport gas hydro, add some vee to the bottom, Remove the sponsons, cut the bow in at the sides, add a bit more vee up front. HUM <_< Yup, still having fun!

No John. You can't do that. That would be a "modified hydro". Remember my sport 45 hydro, got disquailfied from the SAW record it set at the 1990 IMPBA Internats because it had a Mongoose cowl on it! LOL :lol: Oh!...and the beautiful Circus Circus paint job didn't help convince the CD one bit! B)

 

[crfabbro1]

You guys got me thinking now about a flat bottom mono like they use in the full size drag racing. If I cut the sides of my sport gas hydro, add some vee to the bottom, Remove the sponsons, cut the bow in at the sides, add a bit more vee up front. HUM <_< Yup, still having fun!

Dang it you're on to me!

 

[John Finch]

You guys got me thinking now about a flat bottom mono like they use in the full size drag racing. If I cut the sides of my sport gas hydro, add some vee to the bottom, Remove the sponsons, cut the bow in at the sides, add a bit more vee up front. HUM <_< Yup, still having fun!

No John. You can't do that. That would be a "modified hydro". Remember my sport 45 hydro, got disquailfied from the SAW record it set at the 1990 IMPBA Internats because it had a Mongoose cowl on it! LOL :lol: Oh!...and the beautiful Circus Circus paint job didn't help convince the CD one bit! B)

I like that! modified hydro! All you need is a new cowl and your sport 45 is good to go, right? Can't run a rigger cowl on a sport boat! I didn't know we classed boats by the cowl we use.

I already ran the sides of my gas sport hydro through the band saw thus removing the sponson and then ran boom tubes through the hull and re-attached the sponsons to the boom tubes making it a rigger for the next SAW event. Oh No!

 

[Terry Keeley]

I already ran the sides of my gas sport hydro through the band saw thus removing the sponson and then ran boom tubes through the hull and re-attached the sponsons to the boom tubes making it a rigger for the next SAW event. Oh No!

:lol: :lol: :lol:

Pushing the envelope as always, love it!

http://www.youtube.com/watch?v=ad1Umj6hxMw&feature=related

 

[lohring]

Two examples of offshore racing monos. Both were/are winners in their day.

Everything that's illegal in our monos.

1973 old school, but IMPBA legal.

Lohring Miller

 

[hugh hargett]

They both look like too much boat for saw. "1973" funny I was thinking the rules sure promote this 30 plus year OLD stuff. Its been said by many the way to go is to "fly" the boat.Thats cool but that has me wondering why so many newer boats have remove most of their "lifting strakes" which would help promote "flying". WHY?

John I read your post about square struts. I do think they help stabilize a mono thats "flying" coz it would minimize that high speed wobble. Ya ? The flat area that being showed on the keel definately makes for stable "flying" if you will. It seems a square bottom strut is most suitable for a SAW mono. We run them on hydros but it seems that squared corner would trip in the turns alot and have the butt bouncing around.A round bottom seems like it may handle the corners better and make a better heat boat setup.

JAT

Hugh

 

[John Finch]

Round is better for saw and heat racing. Flat struts will slap the water and cause the boat to dive or hop. It upsets the ride of the hull. Tried it many times and always went back to a round strut. Even on the twins. Strakes, while good at slow speeds can cause hull imbalance at speed. Like ailerons on a plane you would think they would add stability but they do just the opposite as when the boat rocks to one side or the other the strakes become more involved in becoming the reaction to the action so to speak. That is why we started removing them towards the transom, to stop chine walk. They do provide grip in a sharp cornering situation and if you have a warped right rear strake that goes all the way to the transom it can even make the boat stand up straight rather than bank hard in a corner. As far as high speed wobble.............our mono hulls don't wobble. That is a thing of the past. Before we understood all the dymanics. One of the worse fixes ever was to bend the strut to the left to stop the boat from steering right. Some people still do that, and at one time we thought that was the right thing to do. It made things worse because after directing the strut to the left it positioned the prop to left of centerline which made chine walk absolutely wicked.

 

[hugh hargett]

Thanks John, Ill be sure to jot this knowledge down in my notes.

Hugh

 

[Andy Greene]

John, I would be interested to know what you guys did to overcome the right hand walk without shimming the strut left ?

Andy

 

[dwilfong]

:huh:

This is how my 39" Cal craft flies with a .80 in it heat racing.

Every thing that should not work but dose.

the strut angle picks up the bow and the lift of the prop picks up the stern.

Break line after the strakes and on a knife sharp perfectly flat V.

Run on the tips of the prop no prop walk.

It works for me.

David

 

[John Finch]

:huh:

This is how my 39" Cal craft flies with a .80 in it heat racing.

Every thing that should not work but dose.

the strut angle picks up the bow and the lift of the prop picks up the stern.

Break line after the strakes and on a knife sharp perfectly flat V.

Run on the tips of the prop no prop walk.

It works for me.

David

david,

I can see where that would work with the trim tabs set like they are so close to the keel. For SAW though if you can make the boat work without the tabs the boat will go faster. There are all kinds of heat racing setups that work if the tabs and rudder and hull each complement each other. Looks like you found a good setup for your boat.

Andy,

What we do now is exit the prop shaft to the right of centerline for heat racing because the prop lifts the boat as well as pushes it forward. If the prop is to the left of the keel it lifts the left side of the boat and makes the torque problem worse. If the boat leans to the right it turns right. If you put the prop to the right of centerline it lifts the right side of the boat and counters the torque that is pushing the right side of the boat down into the water. If the boat leans a little left or neutral the boat will go straight with just the rudder thickness of left rudder. That is heat racing. Dave uses tabs to counter torque, and that works too. We are talking SAW in this thread and that changes everything. For SAW the prop needs to be in the center of the boat because the boat will basically be flying over the water. At that running design there is no hull or tabs to control the attitude so weight distribution, the prop distance to the transom, and the rudder placement are used to trim the boat. Rudders cause lift, so the closer to the keel the rudder is mounted the less it lifts the right side of the boat. The further from the keel the rudder is mounted the more it lifts the right side of the boat. On a heat racing boat rudder location is a lot less of a contributor to trimming the hull as when running SAW. There are things you learn in SAW that you would never learn in heat racing. The day I set the 70 mph 40 mono record my hull leaned to the left at full speed because the rudder was too far the the right side of the transom. Can you picture a record mono racing down the pond leaning to the left instead of the right! After that experience I spent the next 10 years experimenting with rudder location, size, shape etc. Like Terry says........it aint as easy as it looks.

 

[dwilfong]

John I knew you would pick up on the trim tab placement. that is why I showed the pic from the back.

The tabs set this way may work for saw as that will be the only thing in the water at speed.

Also this placement will help with the water flow to the prop.

Kinda think of it as a separate very small boat attached to the back of the boat.

 

[John Finch]

John I knew you would pick up on the trim tab placement. that is why I showed the pic from the back.

The tabs set this way may work for saw as that will be the only thing in the water at speed.

Also this placement will help with the water flow to the prop.

Kinda think of it as a separate very small boat attached to the back of the boat.

Yup! You got it going on. Good to see someone thinking outside the box.

 

[dwilfong]

Put the tabs even closer and use the flat bottom strut as the ride pad.

All legal eagle and the end result is what every one is trying to achieve.

David

 

[Rickard Andersson]

Hey there you saw people , I have a question for you. From the propeller shaft (prop) counted, at which angle of attack relative to the water is the propeller most efficient?

As an example, the bottom of the boat and the transom is at a 90 degree angle. The propeller shaft with the prop is mounted in line with the bottom of the boat. The boat ride with an angle of attack of 3 degrees, when the water brake behind the transom it will deflect upwardly, maby with about X degrees, which means that prop will have an angle of attack relative to the oncoming water by X +/- 3 degrees.

What is better regarding efficency, pos or neg angle, 0 deg or other? If I know this I could build the boat around the prop, prop at a fixed position/angle, to get the most out from the prop!

Rille

 

[dwilfong]

You have to imagine the water coming off the back of the boat.

The way I set the trim tabs makes a channel for the water to come up into. kinda like a hose effect. the prop is then at a strait angle to the water flow at the angle it is set.

take two fingers and run them thew the water and you can see what I mean.

Like the tunnel in my 17' McKee Craft lets it ride in 6" of water at 50mph on the flats. that is where I got the idea.

The eng is mounted high on the transom because the tunnel channels the water to the prop.

Did you run your Cal Craft yet?

 

[Rickard Andersson]

Thanks Dave, yes I have run and race it! That "old design" CalCraft is a very impressive hull. You know, In the real rough water you do "fly" and how I did fly past the other (up to 43") boats. And with "No bad habbits" what's so ever. I will get back to you about It all. I'm very happy with your Engines and the Calcraft hull.

Last year I have bin talking to the people at PropShop in GB, and they did not know anything about my quiss regarding mosts efficient angle of attack for the prop!

Rille

 

[dwilfong]

Thanks Dave, yes I have run and race it! That "old design" CalCraft is a very impressive hull. You know, In the real rough water you do "fly" and how I did fly past the other (up to 43") boats. And with "No bad habbits" what's so ever. I will get back to you about It all. I'm very happy with your Engines and the Calcraft hull.

Last year I have bin talking to the people at PropShop in GB, and they did not know anything about my quiss regarding mosts efficient angle of attack for the prop!

Rille

Great to here it is flying nice.

Funny you never here any one talking about a Cal Craft, just winning with them.

Now you know why thy call some one that drives a boat a pilot.