Protractor fin alignment

illini

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Here's a fin alignment guide that's so obvious I'm sure its been posted here 3,286 times before. However, since it was an epiphany to me, I'm posting it for the 3,287th time. Requires a protractor and a Black & Decker Workmate or equivalent. Here it is: GENTLY squeeze the tube between the two surfaces of the workmate and use the protractor to line up with the fin mount point. Glue on the fin so that it runs through the origin and 90 degree points on the protractor. Make sure it stays there. Foolproof, although this fool only figured it out today. Here's a pic.
 

KarlD

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Cool Idea!

I always use my Trusty "Stanley" Carpenter Square with my fin alignments, but it is a slow process. Your idea sounds quicker.
 

dr wogz

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Cool, thanks, still trying to find a method that works for me..

Wearing glasses (coke bottles) don't help, as all straight lines look curved to me!

How about glueing an expended motor to teh protractor.. think Im gonna try that tonight..
 

Mad Rocketeer

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Originally posted by illini
Here's a fin alignment guide that's so obvious I'm sure its been posted here 3,286 times before. However, since it was an epiphany to me, I'm posting it for the 3,287th time. Requires a protractor and a Black & Decker Workmate or equivalent. Here it is: GENTLY squeeze the tube between the two surfaces of the workmate and use the protractor to line up with the fin mount point. Glue on the fin so that it runs through the origin and 90 degree points on the protractor. Make sure it stays there. Foolproof, although this fool only figured it out today. Here's a pic.
You want to make sure the protractor is centered too. I.e., the line through the origin and 90 degree marks should intersect the center of the tube's circle, forming a diameter rather than some other chord. That's easily enough accomplished by measuring the distance from the origin to the edge of the slot the tube is sitting in (formed by the jaws of the work bench in this case) on each side, making sure the distance is the same for each side. If this is accomplished, it doesn't matter (for this use) if the flat edge of the protractor makes a line through the center of the circle or not.

The tube wouldn't have to be clamped either. It could just rest in a slot of some width smaller than that of the tube, with some means provided to keep it from rotating.

The same protractor could be used to measure 90 degrees or 120 degrees, etc., to see where to put the next fin, but for this use, the line of the protractor's flat edge does need to go through the center, i.e. the tube needs to be supported with the plane of the workbench's deck exactly bisecting the cross-section circle of the tube (if the protractor rests directly on the table).

Clear as mud? ;) :D
 
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