thinned hub?

[76BARRON]

Ron Hill , saw you had a prop on ebay 3-19-05 it was rh,10 7/8-16 w/ thinned hub (inboard/flatbottom)and it got me thinking about what kind of
performance gains a thin hub might offer over a standard(thick) hub? and also if an existing prop can be thinned out or must it be mfg that way?
Is it worth the time and money? or just a race only thing?

[Ron Hill]

In the OLD DAYS we always tested with a Keller Speedometer and we believed that the pick up tube (pitot), which was less than an 1/8 of an inch wide and three and half inches deep, would slow your 70 mph boat a mile an hour...A hundred mile an hour boat has been known to blow over backwards when the pitot was pulled after testing was done...because of the speed gain. The speedo tube effects performance that much.

The strut is dragging through the water at all times in an inboard....Lance Hazelrig's GN is one of the few GN's with a 1 inch shaft....and Lance wins many GN races...Everyone else runs an inch and an eighth.

I'm not sure who started it, and I'm against it, but the Super Stock top runners have all gone to 7/8 shafts...The strut is 1.330. Now what I found was, that my hubs on my good Super Stock wheels measured 1.550. So, I milled the sides off about .120 per side...

At 110 mph an eighth on an inch is a lot of drag...

Outboarders, for years, have filed on their gearcases....because they knew there was speed to be gained with less drag. This is why outboard have very strick rules on their gearcases. (Even Formula One)...

When you spend $35,000 for a Super Stock engine, everything is important...For river racing.....it won't hurt to have a shaved hub.

Yes, we set the prop up in the mill and milled flat spots on the side. So, I could thin your hub, too. I also, made a new mold with a small hub....This props was a 7/8 prop, but I think my new casting will be fine with a 1" hole...

I've just milled my four blades, as they were faster, but slowed quickly in chop (A sign the hub is too large)....and slowed too fast when backing out of it...another sign the hub is too big.....

Ask yourslef this..would you rather shave with a sharp blade or a dull one? Thinner strut/hub cuts through the water easier, resulting in a speed gain.

Hey, thanks for asking...Hope I answered your question...

[76BARRON]

On a 90ish mph v-drive would it be fair to expect 1-2 mph with hub thinned?
and what would the cost of machine work be? This would be on one of your
ss 2 blade props.

Anouther question I have is ...Your stainless steel, 2-blade,v-drive prop is it a cast prop or is it forged or billet of some type?
I am just trying to compare to a carbon steel or welded ear prop in the strength area.

[Ron Hill]

Go measure the width of your strut. A seven eighths shaft has a strut of 1.330...My props were like 1.550. A one inch shaft strut will be, about 1.500. So, thinning the hub on a one inch, or thinning my hub won't help you.

Everytime I've considered changing materials or using something else, the question always comes back to what is wrong with what you are using? My first inboard casting were made in 1977. Doug Lightfoot won the GN Championships in 2004 with one of those 1977 props...in fact, looking at it, I'd forgotten one of my old speed secrets..and that was the relieved hub...

[76BARRON]

You are correct,my strut is more like 1.610 so I won't worry about the hub.
However as Grasshopper learns from the Master.......I see a 1.500 dia
rudder bushing sticking thru the hull about .270 ..look's to grass hopper like there is room for improvment? Does Master Agree? :D

[Ron Hill]

Same with fins, water pick ups....stick your head under SS 80.....She's pretty on top, but she is streamlined in eveyway on the bottom....

Every lit bit counts said the old women as she spit in the ocean... Big THINGS don't win races...many little things do...

Just think a 7/8 strut is 1.330....your strut is .280 thicker (Wider).....250 is a quarter inch...holly cow, no wonder a 7/8 shaft is faster....probably 4 mph at 100!!!