Re: sailing upwind?

["P. O. Johnson" <pojhome@FLASH.NET>]

John, you made my point. To be sure, turning the fan around to blow aft
creates a forward reaction force on the fan which accelerates the fan, the
deck, and the entire boat forward. Likewise, aiming the fan forward so it
blows into the sail creates an aft reaction force on the fan which
accelerates the fan, the deck, and the entire boat aft.

poj

----- Original Message -----
From: "John Mallinckrodt" <ajmallinckro@CSUPOMONA.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Thursday, December 30, 1999 1:20 PM
Subject: Re: sailing upwind?


> Not at all; you just have to have a sail that manages not merely to
> *stop* the air blown at it by the fan, but to "turn it around and send off
> in the other direction.  One that should do this quite nicely might look
> like this:
>
>             -
>               \
>                |
> air   -->     /
> from  -->  --      <- sail
> fan   -->     \
>                |
>               /
>             -
>
> The same effect *can* be accomplished by simply turning the fan around and
> losing the sail, but doing it this way is perhaps a better illustration of
> the power of momentum conservation as an analysis tool.