Holes in the hull and Logs

[tom52]

Fed up with having to take out my log to remove the clog of weed and creatures from the impellor every week I wondered why it has to fitted through a hole in the hull.
Why can't it be clipped on to the transom and just raised out of the water when not in use ?

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[Talbot]

you can get some like that, but they are not so accurate, you can also get a solid state version that replaces the impellor, but it only works with some logs, and it is expensive.

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[boatmike]

There iso a very novel way of chucking a knotted rope over the transom and counting the knots as they go out...... That works OK!

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[mirabriani]

Sometimes forumites ask a question that, on first glance, may be dismissed as frivolous. Not that I am suggesting this is the case mind. However I was thinking.....Why not? OK it will probably not be accurate in the position you suggest
but are they not adjustable? Even if not, you might choose to live with it. In fact I know my log is under-reading by about 30% I just mentaly adjust for it, or use the GPS
With a bit of thought it could work well. Fit it mounted on a flat plate like a trim tab. detachable if you wish, you could be on to something
Regards Briani



<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by mirabriani on 31/08/2004 19:25 (server time).</FONT></P>

 

[qsiv]

Surely it would be out of the water as often as in it?

And, (to abuse the languge) you would need one for each tack, as modern waterplanes will rasie the transom out of the wwater when heeled, so now we need a mercury switch to effect the change over. Now we're in fun territory as we need two set of calibration data, one for each tack. B&G can do it, but no others that I am aware of - and having struggled for two days to get the calibration of a dual sensor B&G to be accurate before Cowes Week, I wouldnt wish it on anyone!

If you dont want the hassle of cleaning paddlewheels, bite the bullet and go ultrasonic!

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[Vara]

Stowe used to do one that involved throwing an impeller over the side attached to wire,the electrical version of the Walker log.Used a 9 volt battery which lasted for 18 months,occasionally in very heavy weed it used to foul;you just pulled it in and shook the weed off.No holes in the hull, no calibration;it just worked.
Disadvantages; couldn't be interfaced with anything other than the brain,and you had to remember to take it in before engaging reverse.
I believe that most of the Yachting mags used to use them on boat tests to verify speeds.
Progress?If I could get one now I would snap it up.

<hr width=100% size=1>If it can't be fixed with a lump hammer dont fit it!

 

[simonfraser]

i tow mine fitted through a bit of black guttering with an apropriate bend in it, i know it's not very boaty, but it works well and matches with the GPS, so why do we bother ???????



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[tom52]

I am kind of thinking out loud now but.....
It need not be close to the surface it could be on shaft that was a couple of feet long and and mounted centrally to minimise the heeling effects?
Why would it be less accurate ?
If prop wash was a source of inaccuracy could it not be on slide on the stem?
Are trailing electronic logs no longer available other than for sophisticated testing equipment ?

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[MainlySteam]

You may have to experiment until you found a transducer that would be accurate on the end of a pole. As far as I know, most (if not all) name brand ones are designed to work in the laminar flow against the hull.

I would have thought it would have been easier removing a transducer from the thru' hull each week before the boat sits, than it was to muck around with having and removing a pole and cable at the stern.

John

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[tom52]

Yes, you are probably right, but all that water rushing in through the hole !
Maybe I am just a pessismist but one week I am going to crossthread it, or strip the thread and then........

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