Barrelback-20 Louisville Kentucky

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CarlM
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Re: Barrelback-20 Louisville Kentucky

Post by CarlM » Wed Jul 31, 2019 4:32 pm

Kens,
Ideally speaking what would be the best setup for a 351? That is what I am planning on obtaining for my Gentry build.

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kens
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Re: Barrelback-20 Louisville Kentucky

Post by kens » Wed Jul 31, 2019 6:08 pm

For a Gentry or any of the mahoganys, with a V8, a 1:1 gear
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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Mr Hot Rod
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Re: Barrelback-20 Louisville Kentucky

Post by Mr Hot Rod » Wed Jul 31, 2019 6:24 pm

I agree with Ken that most Glen-L designs are light enough that a reduction gear is not required.

The first step to select the engine, gearing and propeller for your boat is to determine optimum propeller diameter. The following Excel spreadsheet uses the Diameter-HP-RPM Formula from Dave Gerr's Propeller Handbook to find optimum propeller diameter from HP and RPM.
Download the spreadsheet and input your specs to see what is recommended :
More light reading from our website :
Hope this helps !
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Bill Edmundson
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Re: Barrelback-20 Louisville Kentucky

Post by Bill Edmundson » Wed Jul 31, 2019 6:25 pm

Usually, set this up with a 12x12 prop.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
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CarlM
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Re: Barrelback-20 Louisville Kentucky

Post by CarlM » Wed Jul 31, 2019 7:34 pm

I appreciate the information. Thank you gentlemen!!

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kens
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Re: Barrelback-20 Louisville Kentucky

Post by kens » Thu Aug 01, 2019 4:37 am

Those charts are not telling enough input to arrive at an answer.
You must know the size of the boat to determine prop diameter and gear ratio from a chart like that
Without entering size of boat those charts dont do much.
The problem Monitor has, is he wants to prove or disprove about his 1.5:1.
The above chart doesn't input his Barrelback information to relate it to a reduction gear, or not.

In simplest of terms the formula is something like:
size of boat + HP = gear ratio,
then, size of boat for a given HP relates to a expected speed
then, expected speed relates to a gear ratio
then, expected gear ratio relates to prop diameter

Hense, a small boat with big HP has no gear ratio or common 1:1 (go fast with small prop)
Larger boat with same HP has reduction gear (go medium speed with medium size prop)
Larger boat yet same HP gets deeper gear ratio (go slower with larger prop)
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

monitor
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Re: Barrelback-20 Louisville Kentucky

Post by monitor » Thu Aug 01, 2019 5:58 am

Do you guys know if the bell housing and shaft coupling on the Ford 351 work with the Velvet Drive from the Chevy 454 engine? (I'm not sure of the terminology). Or will I need other parts?
Jim Kinsella

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Jimbob
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Re: Barrelback-20 Louisville Kentucky

Post by Jimbob » Thu Aug 01, 2019 10:38 am

michigan motorz did a conversion on my engine from an i/o to the velvet drive transmission.
It required a different bell housing. You might give them a call, and get you the proper bell housing if you need one. I'm guessing that you probably will need a different bell housing.

On this other prop stuff. I would try the prop you have with the existing setup. The main thing to remember is that the top speed on our barrelback design is about 40mph. You will probably be cruising between 20 - 30 mph. High speed is something we don't have to worry about. I have been in tournament ski boats an their top speed was about 45mph. (they are designed for pulling) You can always change props later after you try the boat out. If I remember correctly on my 5.7L runabout, the rule was that if you had the proper prop you should be able to attain 4800rpm at wide open throttle. Some times you need to try different props to find the "sweet spot".
I had two props. One was a 19 pitch (a stump puller for pulling up skiers) and a 21 pitch for crusing and high speed. The pitch relates forward motion of the boat with each revolution. i.e. 19 pitch meant that you went forward 19" for each revolution. (acts like a lower gear). The 21 pitch meant that you went 21" forward with each revolution. Some retailers allow you to try out different props.

Jim
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Building a Barrelback in Sacramento, CA
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Mr Hot Rod
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Re: Barrelback-20 Louisville Kentucky

Post by Mr Hot Rod » Thu Aug 01, 2019 10:40 am

kens wrote:The above chart doesn't input his Barrelback information to relate it to a reduction gear, or not.
  • The first step to select the engine, gearing and propeller for your boat is to determine optimum propeller diameter. Gerr doesn't need boat length or weight to do this. The diameter check ensures that the propeller diameter falls within an acceptable range. In the sample output provided, we've specified a ratio of 1.25:1 and compare it to a 1:1 ratio. You might have missed it, but we encouraged the OP to download the spreadsheet from our website and input his own data.
  • The second step in the process is to determine gearing and propeller size to attain a desired speed. This will require more input such as length, displacement, Crouch's Constant and desired maximum speed etc.
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Bill Edmundson
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Re: Barrelback-20 Louisville Kentucky

Post by Bill Edmundson » Thu Aug 01, 2019 11:31 am

The Tahoe displacement is right at 2000 pounds. I have a 115 hp diesel that turns 3800 rpm with 1.23 reduction, srpm is 3170. My prop is a13x16. I get almost exactly 10 mph for each 100 rpm of engine rpm.

The BB20 should be very similar numbers. Because of configuration 13" was as large as I could go.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
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kens
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Re: Barrelback-20 Louisville Kentucky

Post by kens » Thu Aug 01, 2019 11:38 am

monitor wrote:
Thu Aug 01, 2019 5:58 am
Do you guys know if the bell housing and shaft coupling on the Ford 351 work with the Velvet Drive from the Chevy 454 engine? (I'm not sure of the terminology). Or will I need other parts?
The bellhousing and drive damper will stay on engine. The drive damper for Velvet drive is all the same, as is bellhousing bolt pattern.
Whatever drive damper you use will stay on the flywheel, and the drive splines are standard velvet drive.
transmission mounts are all the same bolt pattern
Shaft coupling flange you will have to measure, but, I think you can swap out
please post a pic of each data plate on each transmission and we can sort it out.
Correct me if I am wrong but a 72c 1:1 used a 5" flange
71c 1: used a 4" flange
71c reduction gear 5" flange

post a pic of data plates, we can tell you what you need
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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kens
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Re: Barrelback-20 Louisville Kentucky

Post by kens » Thu Aug 01, 2019 11:50 am

Paul wrote
"The first step to select the engine, gearing and propeller for your boat is to determine optimum propeller diameter. Gerr doesn't need boat length or weight to do this."

yes he does, the size of boat is how you arrive at gear ratio.
if you do not figure the size of boat, 'which you need to get the ratio', then you are blindly throwing darts at the wall.

.......read his book again,,,and again if you have to.
Gerr wrote that book with a sharp pencil.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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Mr Hot Rod
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Re: Barrelback-20 Louisville Kentucky

Post by Mr Hot Rod » Thu Aug 01, 2019 5:40 pm

Good call, Ken !

Tricky little spreadsheet estimates SHP as BHP * .097. This is why I said that Gerr doesn't need boat length or weight to do this. Good enough if all you want is an estimate. True SHP requires Desired Speed (knots), Crouch's Constant and Weight.
  • SHP = BHP * 0.97

    SHP required for given speed = ( Kts / C )^2 * LB

    Optimum Diameter = 632.7 * SHP^0.2 / SRPM^0.6

    Kts = C / ( LB / SHP )^0.5

    Where :
    • SHP = Shaft HP
      LB = Weight (Pounds)
      BHP = Brake HP
      Kts = Desired Speed (Knots)
      SRPM = Shaft RPM
      C = Crouch's Hull Constant
Taking a shortcut will bite you every time !

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Paul Kane
Kane Custom Boats Ltd.
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kens
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Re: Barrelback-20 Louisville Kentucky

Post by kens » Thu Aug 01, 2019 6:30 pm

Paul wrote:

SHP = Shaft HP
LB = Weight (Pounds)
BHP = Brake HP
Kts = Desired Speed (Knots)
SRPM = Shaft RPM
C = Crouch's Hull Constant

you say Kts = desired speed (Knots)

So, umm, how do you get THAT number????
where did you get that? what is it? 20kts, 30kts, 40kts, 50kts???
show me just how to arrive at that number.............
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

monitor
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Re: Barrelback-20 Louisville Kentucky

Post by monitor » Thu Aug 01, 2019 6:44 pm

Looks like that 1to1 tranny is coming out of the Supra! It has a nice prop shaft, strut and flange on it also. Shaft may not be the correct length of course. Glad I purchased the Supra now!
Let me get it out and I will get back to you guys...thanks again.
Jim Kinsella

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