[Alberg30] At4 propulsion and the A30

[George Dinwiddie]

Scott,

You've got a 10x6?  You know that the original prop on an Alberg30
with an Atimic 4 was a 13x7 two-blade.  That's what I have and it
seems to work sufficiently well, cruising at 1700 to 1800 rpm.

I know the prop experts say this is too much prop, and a smaller 
prop will let the engine get further up its power curve.  And I 
know they say there's too little tip clearance in the aperture
and it will cause cavitation.  But in spite of that, it seems to
work pretty well.

I'd try a bigger prop before moving the engine.

 - George

> Scott said:
> 
> 	Hey- want to throw this out there and hopefully have a response. I, like
> many others are unsatisfied with the at4 performance in the A30. However the
> 10k investment with a diesel exchange is not feasible for many. I have
> recently rebuilt my at4 engine. It purrs, easily serviced and love the
> simplicity. My present prop is a 10x6-3 blade. Works great at 2000rpm, no
> sea conditions, clean prop and bottom.  =5KTs. any sea and its back to 4Kts.
> The 10" wheel really has minimal blade exposure behind the keel. My thought
> this haul-out was possibly sliding the engine forward some 3" and installing
> the reduction gear. The question to diesel owners is then.... What  wheel
> size (prop and pitch) do you have and what shaft RPM do you estimate at
> cruising engine RPM.   This is to assume that diesel engines have a 2:1
> ratio. My figure would be a at4 engine running at say 2500 rpm at more up
> with its 80% efficiency curve, larger blade with more surface for bite. an
> engine on motor mounts?   any thoughts   Scott   Thanks

-- 
 ----------------------------------------------------------------------
  George Dinwiddie                             gdinwiddie at alberg30.org
  The gods do not deduct from man's allotted span those hours spent in
  sailing.                                    http://www.Alberg30.org/
 ----------------------------------------------------------------------


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