[alberg30] Prop size for Atomic 4

[Forhan, Thomas]

From: "Forhan, Thomas" <Thomas.Forhan at mail.house.gov>

I too have a 13x7. At about 1500 rpms, we are going hull speed. Any more
throttle and 
the stern just starts to squat. From the hp charts for the atomic 4, it
seems like anything more
than about 18 hp and it just wasted away digging holes in the water.

> -----Original Message-----
> From:	Robert Kirk [SMTP:kirk at neptune.gsfc.nasa.gov]
> Sent:	Tuesday, November 16, 1999 12:37 AM
> To:	alberg30 at onelist.com
> Subject:	Re: [alberg30] Prop size for Atomic 4
> 
> From: Robert Kirk <kirk at neptune.gsfc.nasa.gov>
> 
>  Jim Davis wrote:
> 
> >13x7 two blade is the stock prop.  While a smaller prop will give you
> more 
> >RPM's and more horsepower, you will loose the push from the larger
> diameter.  
> >Quite a few of us have tried different props to get the RPM's up, but it 
> >seems most have returned to the 13x7.  I tried a couple combinations on
> Isa 
> >Lei and for flat water the smaller size worked well.  However when I had
> to 
> >power into any sea, the smaller diameter just lacked the push.  This
> isn't 
> >scientific, just observations.
> 
> 
> Jim... That doesn't sound right.  If you pour more power into the water it
> should push the boat harder/faster.  Unless you generate more cavitation
> or
> turbulence than thrust?  Of course, what I don't know about props is vast.
> I too, have the 13 X 7 which chugs along nicely behind an Atomic 4.
> 
> Bob Kirk
> Isobar #181
> 
> 
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