Better water flow reshaping

[Nomad Willy]

WOW ......
Ya did it.
Looks good and no doubt even better w some paint. When will you know if it did any good re vibration or efficiency? I'm kinda thrilled that you did it.

It's a bit of work but not that hard on a steel boat. Went through some rod I'll bet.
Is that prop a Michigan MP series. Looks like you've got plenty of pitch and I like to see that.

 

[funangler]

Started with stick and had to switch to a flux core mig welder. Burn through was pushing my mental limits. The boat should go in about mid March. The prop is original from 1984 it 24 diameter with 22 pitch. Transmission is hurth 2:1. I will report back when she floating.

 

[what_barnacles]

Nice work. I like the horizontal stiffeners.

 

[sdowney717]

Like this....

View attachment 46558

This looks better to me, so why are people not opening up the clearance from prop to keel using the curve design versus just tapering the keel end straight?

If you go to all that work anyway then why not. they think it is too hard?
Maybe if you make a pattern form, then a metal shop could fab the pieces. Then you cut out the keel and weld in the new metal. Looks like a flat cut plate into which is pressed the concave surface. So I am thinking you need 4 pieces of steel shaped.

 

[stubones99]

If it was done at a sheet metal / machine shop, then the filler sections could be rolled slightly, then trimmed where they meet and provide Tad's nice prop clearance.

What he did was boatyard metalworking. Better than before but not as sexy as Tad's design. With the top end being rather slow, it should still perform properly. It would have been better / quieter had he cut back a bit of the metal near the leading edge of the props.

 

[funangler]

Without a metal fab shop onsite it becomes very trick and expensive to get it right. I would be surprised if I could get those part for less then a grand and the fit up would be tough. I will look into to reshaping them into more of a radius. I have to use a sawall to cut it that will be no fun! On second thought the boat only goes 8 knots I'm done. If I have still have the boat in 15 years and need to redo the keel I will do it then.

 

[Nomad Willy]

sdowney717,
Not that simple unless you've got all the right stuff like the machine of rollers that can bend sheet or plate in a curve. I thought funangler could have used a pipe cut just so for the prop shaft part but then after thinking about it decided cutting it even as a straight taper would add significantly to the time building.

No ... I think funangler did good. There will be slight turbulence along the top and bottom of the taper and in the center. A little turbulence around the prop hub is fly stuff. But the working part of the prop is above and below that level so probably no loss in efficiency will result ... not worth talking about anyway. The important thing is getting it done and FA got it done. I'd like to do it to but haven't. FA got it done.

 

[Ski in NC]

A rosebud and hammers can shape that plate. Heat and beat!!!

But given the tools at hand, I think Funangler did a pretty good job. As posted before, I think the boundary layer developed along the many feet of keel ahead of the prop is likely causing more turbulence than the shape of the keel bitter end. But certainly good to fair it as much as you can.

 

[Martin J]

Why not install a drive saver in the connecting flange? It would move the prop back an 1 inch plus and see if there is any improvement before radical surgery?

Seems a quick and easy check and you could do it in the water.

 

[funangler]

I installed an aqua drive a few years back it's impossible to put Drivesaver in I made sure that the prop clearances is adequate now. I'm hoping she'll behave a little better in reverse. Just finished putting the first coat of Epoxy paint on it.

 

[funangler]

I think I will obtain a reduction in vibrations just because that area is super strong now.

 

[Nomad Willy]

It looked quite flat in the pics ...

Perhaps there was "oil canning" on the sides of the old keel?

 

[funangler]

The reshaping of the area ahead of the prop has been tested. I will say it exceeded my expectations. The boat is quieter with hardly any vibrations at cruising speed. The bonus I was hoping for was a boat that could back nicely. I can now back up with the rudder straight and continue to go back straight. Before this project I was always avoiding backing up the boat was horrible at it. Thanks for everyone's words of encouragement.

 

[Panope]

Funangler, Thanks for the follow-up and congratulations on a successful modification. Those are the best kind.

Steve