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Re: electronic stud finder to detect roof joists?



    Just some thoughts from someone who has never see plywood shingles used
as a roof cladding material (though I have heard you do things like that in
the USA).

    I assume you have joists which are similar to those used to support a
tile roof or a sheet metal roof. If the joists are straight, (I assume you
would put plywood shingles on in a way similar to terra cotta roof tiles)
why not place a small mark (using a felt tipped pen) on top of the bottom
shingle when it is first put on (when you can see it) to indicate where the
centre of the joist is and then again mark the top shingle indicating the
centre of the joist before the ridge cap is put on while you can still see
the joist. You could then located the position of the joist by pulling a
string between the marks. If you mark the joist locations in this way in all
the likely locations you would mount your antennas it should be quite easy
to bolt into the joists.

Regards,
Murray Peterson
VK2KGM
Sydney NSW,
Australia

----- Original Message -----
From: "Estes Wayne-W10191" <W10191@motorola.com>
To: <amsat-bb@AMSAT.Org>
Sent: Thursday, January 25, 2001 4:04 AM
Subject: [amsat-bb] electronic stud finder to detect roof joists?


> This spring I will take down all my roof antennas in order to get a new
roof installed.  When I put the roof tripods back up, I want to ensure that
the lag bolts engage the roof joists whenever possible, not just the plywood
roof sheathing.  One tripod will be in an area where there is no attic
underneath because of a cathedral ceiling.  Consequently, I don't have the
option to add any reinforcement from underneath the roof.
>
> Electronic stud finders detect a change in dielectric constant when you
move the stud finder to an area that has a wooden stud behind the wall.  I'm
curious if anybody on this list has successfully used an electronic stud
finder to locate the joists under a roof.  I think the change in dielectric
constant would be much more subtle when you have to sense through the
thickness of the shingles and a layer of 1/2 inch plywood (composition
shingles, not wood shingles).
>
> I suppose I could just buy an electronic stud finder and return it if it
doesn't work.  But it would be nice to know in advance if it's likely to
work.
>
> Wayne Estes W9AE
> Mundelein, IL, USA
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