Homemade hygrometer

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Homemade hygrometer

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bugeyed

Posts: 56
Joined: Aug. 24 2009
From: Conroe, Texas

Homemade hygrometer

I looked at a thread started by Per Hallgren detailing his homemade hygrometer & all of the pictures have been removed. Does anyone know where I can find these? If anyone dnloaded them, can you post them again?
Thanks,
kev

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REPORT THIS POST AS INAPPROPRIATE | Date Jan. 4 2010 16:26:26

kovachian

Posts: 506
Joined: Jan. 30 2008
From: Americanistan

RE: Homemade hygrometer (in reply to bugeyed)

Did it happen to use a few strands of hair and look anything like this? I made something similar for my 6th grade science fair, and it actually worked, much to my surprise.

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REPORT THIS POST AS INAPPROPRIATE | Date Jan. 4 2010 20:51:27

r0bbie

Posts: 160
Joined: Feb. 11 2007
From: Holland

RE: Homemade hygrometer (in reply to bugeyed)

Hi,

Unfortunaly I did not download them but maybe you could ask him to put some pictures on this forum?

I remember he made one and I asked how he did it. It seemed quite "simple" one thin stick of spruce with the grain length wise and glued on to that a thicker piece of spruce with the grain perpendicular to the length.

If I remember corectly, he used super glue to prevent water from a water based glue entering the wood and offset the hygrometer.

Cheers,
Rob.

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REPORT THIS POST AS INAPPROPRIATE | Date Jan. 5 2010 13:38:50

bugeyed

Posts: 56
Joined: Aug. 24 2009
From: Conroe, Texas

RE: Homemade hygrometer (in reply to bugeyed)

I have PM'd Per. FYI here are his instructions sans photos.

Cheers,
kev

"However it is quite easy to make a wooden hygrometer so why don't you? You need some spruce as wide and long as you want the wooden stick to be long. 15 cm x 15 cm is fine. Glue two pieces together with the grain crossed 90 degrees using polyurethane glue. Thin one of the layers almost to the glueline but be sure to leave ca 0.3-0.5 mm. Thin the other layer to ca 2-3 mm. Cut strips ca 5 mm wide so that the thin side spruce is long grain along the length of the stick and thus the thick side is cross grain. Finish sand gently without breaking the stick. Glue one end of the stick on a surface but be sure that the rest of it is free to bend. Refer to the pictures below.

Now that you have understood the principle behind it you can use other dimensions on the spruce. You don't need to use two similar sized pieces as long as the cross grained side is the thick one and the long grained is the thin one. If the stick is made only ca 5 mm wide it will react faster than if it is made wider. What is important is the the wood shall have reached equilibrium moisture content for the relative humidity that you want the stick to be straight in, i.e. that the wood is not gives or takes moisture from the air in the room where it is and will be the reference. This will take some time, hours, days or months depending on dimensions of the wood and how dry it is from the beginning."

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REPORT THIS POST AS INAPPROPRIATE | Date Jan. 5 2010 15:52:53

Per Hallgren

Posts: 241
Joined: Jul. 1 2006
From: Sweden

RE: Homemade hygrometer (in reply to bugeyed)

Here are the photos of the hygrometer. I think they are self explaining.

I removed the photos in a moment of irritation over getting a lot of emails from people wanting me to explain details in guitarmaking. It wasn't you guys at Foro Flamenco but people from some swedish guitar forums. The internet sometimes seem to give people the belief that everything is free to take or demand, but my life is too short to serve everyone who wants to build a guitar. It's not about money but time. However, most of the photos can be seen at my website now. http://www.hallgrenguitars.com/Per_Hallgren,_Guitarmaker/The_workshop.html

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REPORT THIS POST AS INAPPROPRIATE | Date Jan. 5 2010 23:37:31

Exitao

Posts: 907
Joined: Mar. 13 2006
From: Vancouver, Canada

RE: Homemade hygrometer (in reply to bugeyed)

So essentially this is like the bi-metallic piece in a thermostat, except the differing grains force the curvature of the wood.

The swelling or contracting of the thicker horizontal grain side forces the curvature.

It seems that having access to an hygrometer for the initial setup is prerequisite...

And I don't think this design would fit in my guitar case. :-P

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REPORT THIS POST AS INAPPROPRIATE | Date Jan. 6 2010 0:15:25