Planimeters

[seanconnett]

Here is another newbie question.
Having learned a little about planimeters and trying to decide which one to buy, A question comes to mind.
Lasico has the 10, 20 and 30 models. The 10 and 20 do not come with an adjustable pole arm but they are available as an option. Is an adjustable pole arm a big plus when it comes to using the planimeter? Is it worth the extra cost?
Your opinions are appreciated
v/r
Sean

[mmd]

In twenty years of design work I have never needed that feature on my planimeter. Just one person's opinion...

[SailDesign]

Sean,
Anything that CAN be adjusted will NEED to be adjusted. Constantly.
20-plus years of using an adjustable have taught me to glue the arm in one place and use fiddle factors. ;-)
Steve

[Paul Browne]

Weston Farmer describes a knife blade planimeter in his book "From My Old Boatshop". He says it can be built for 50 cents. I suppose that might be a buck these days. Have you seen it? I've sent a photo to my member's gallery, and it should be posted shortly, presuming it's approved.

Paul Browne

http://www.boatdesign.net/gallery/showphoto.php?photo=1124

[Guest]

Paul -
Yes, I have seen the Knife Blade Planimeter by Westy Farmer. It was his own. Westy was a dear friend and teacher of mine until his death. The planimeter works but is not as smooth in operation as a production model. It was inspired by Sam Rabl ingenuity who Westy admired mightily. It is accurate enough to build a small boat but I would not count on it for an 82 footer. Try it. you'll like it.

David Robb
non-member

[Paul Browne]

David,

You are fortunate indeed. Most of us have to be content with Weston Farmer's designs and writings. You've got memories of him much richer than that.

Cheers,

Paul

[edneu]

I wouldn't bother with the adjustable arm. I have a Lasico mechanical planimeter and it is a good insturment but a little hard to read late at night with bleary eyes. The adjustment on the pole arm makes it mind boggling in my opinion.

I also have a PLANIX electronic roller planimeter which I got on eBAY for $100. It is great, it averages measurements for you and is really easy to read, it also does the scale conversions. I think they are very expensive new, but I was lucky to get one very cheaply and reccomend it highly.