Another Roundnose Question

[Ray Barnes]

I'm in the proccess for the second time redoing the bottom of my 68 Bardahl to try to improve the attitude of the boat. It will run fine wide open but when I have to slow to a mill speed and try to bringing it back up on plan... forget it. The sponsons have been stepped and are currently 1 1/4" deep at the sponson transom. I put the step in to add a 3 degree attack angle and a 2 degree dihedral. I have some pics in my gallery of the first go around. This time add a more pad to bring it up. The sponson depth in the gallery is at 1". Is the sponson depth to deep by bringing it up to 1 1/4"? I aslo have a belly pan that is a 5/8" deep would that cause any issues?

 

[FloridaScaleBoater]

Ray, what is the width of the ride pad.

That I feel is the key, you would need a wide enough pad tp support the hull weight

I would think 1" sponson depth would work just fine

If you lower your sponson depth, you are going to reduce the width of you pad even more

I am running right at 1" to 1-1/16" depth

Again, just my opinion

Rick

 

[SayMikey]

Ray, what is the width of the ride pad.
That I feel is the key, you would need a wide enough pad tp support the hull weight

I would think 1" sponson depth would work just fine

If you lower your sponson depth, you are going to reduce the width of you pad even more

I am running right at 1" to 1-1/16" depth

Again, just my opinion

Rick

What motor,pipe strut width and prop are you using? You may be chasing the wrong end

 

[Ray Barnes]

If I remember correctly the pad width at the rear is 2 1/4"

I did have the pads at 1 1/16" deep and the she wouldn't come up unless it was thrown real hard and thier was now way you could slow down without the nose going under.

ENGINE: CMB Greenhead, stock carb, CMB Needle, no engine mods

PIPE: Steve Muck pulled out to 11 3/4"

PROP: Octura x457 2 blade.

STRUT: Speedmaster round bottom dropped to 1 1/2" at bottom at the prop

SKID FIN: I made it . Looks like a Tyndall but is straight down with curve at the bottom edge. Less agressive than a Tyndall. I have tried a Tyndall but would loop out at the end of the turn.

I'm also thinking that maybe the skid fin might have something to do with it. The boat tends to have the right sponson drop deeper on low speeds and plows water. I made a straight fin that was tilted in 15 degress it still did the right sponson drop but wouldn't hold very well in the corners.

 

[SayMikey]

If I remember correctly the pad width at the rear is 2 1/4"I did have the pads at 1 1/16" deep and the she wouldn't come up unless it was thrown real hard and thier was now way you could slow down without the nose going under.

ENGINE: CMB Greenhead, stock carb, CMB Needle, no engine mods

PIPE: Steve Muck pulled out to 11 3/4"

PROP: Octura x457 2 blade.

STRUT: Speedmaster round bottom dropped to 1 1/2" at bottom at the prop

SKID FIN: I made it . Looks like a Tyndall but is straight down with curve at the bottom edge. Less agressive than a Tyndall. I have tried a Tyndall but would loop out at the end of the turn.

I'm also thinking that maybe the skid fin might have something to do with it. The boat tends to have the right sponson drop deeper on low speeds and plows water. I made a straight fin that was tilted in 15 degress it still did the right sponson drop but wouldn't hold very well in the corners.

Turn the boat upside down and put a straight edge across the sponson rear,how much distance to the belly pan? Where does the boat cg at?

 

[Ray Barnes]

I did that last night, it sits at a little less than 3/4" (.72") from the sponson bottom to the bottom of the belly pan.

The balance point is at the center of the skid fin. I will get an exact dimension from the rear transom forward.

 

[SayMikey]

I did that last night, it sits at a little less than 3/4" (.72") from the sponson bottom to the bottom of the belly pan. The balance point is at the center of the skid fin. I will get an exact dimension from the rear transom forward.

Send me a pic of the boat bottom, and put a straight edge on the strut and snap a pic...send to [email protected]. Im going to Indy the 8-9 any chance your coming? Mike

 

[Ray Barnes]

I can't make that race. I hit a bouy last night testing, she cartwheeled a couple of times and did some damage to the the top of the deck plus the whole bottom is in filler and primer. I tried racing awhile back but had these same problems I'm trying to fix. I will try to get those pictures this weekend. My home computer isn't working very well I'll send them from work. I do appreciate your time and help on this.

 

[SayMikey]

I can't make that race. I hit a bouy last night testing, she cartwheeled a couple of times and did some damage to the the top of the deck plus the whole bottom is in filler and primer. I tried racing awhile back but had these same problems I'm trying to fix. I will try to get those pictures this weekend. My home computer isn't working very well I'll send them from work. I do appreciate your time and help on this.

Another thing be sure to knock the shine off the sponson bottom.

 

[FloridaScaleBoater]

Hey Ray;

Just today had a chance to measure what I have for sponson width on my boats.

I thought 2-1/4" sounded narrow, on my 3 hulls the sponson width's range from 2-7/8" to 3-1/16"

I don't think you have enough surface area to support the hull at slow speeds, them there is not enough available power to get the hull back up out of the water.

Again, I don't think changing the sponson depth is the direction you need to be going, because as you lower the sponson, your ride pads are going to get narrower, and make the problem worse.

Just my thoughts on the situation

Rick Bellinger

 

[Ray Barnes]

I did that last night, it sits at a little less than 3/4" (.72") from the sponson bottom to the bottom of the belly pan. The balance point is at the center of the skid fin. I will get an exact dimension from the rear transom forward.

Send me a pic of the boat bottom, and put a straight edge on the strut and snap a pic...send to [email protected]. Im going to Indy the 8-9 any chance your coming? Mike

Sorry it took so long to get back, I was on vacation over the weekend. I have some pictures in my gallery showing some of the dimensions if you need more let me know. Thanks again.

https://www.intlwaters.com/gallery/displayimage...m=898&pos=4