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Plans shrink? Plans building & Tools questions?

Posted By:
Daniel Findling
Vintage Aircraft Association MemberHomebuilder or Craftsman
55
Posts
21
#1 Posted: 9/15/2010 09:57:19

A few questions for seasoned builders.

I am studying plans/preparing to build ribs for a Hatz Classic Biplane and copied the full scale rib outline to glue to my rib building template.  The ribs are a Clark Y airfoil with a 50" chord.  I measured the full scale rib outline from the tip of the leading edge to the trailing edge and it measures approximately 14 3/4".  The plans do not have coordinates for the airfoil except for the spar width etc.  The spar is .75 inches.  I have Tony Bingeles books (sp?) and could not find the answer.

Question group #1:  Is it acceptable to build the wing a 1/4" short as long as the spar width etc. is held to plans or do I cut the plans by the trailing edge and extend the template 1/4"?  Is there another solution?

Question group #2:  I have limited wood working tools.  The truss in the ribs are 1/4" spruce.  Should I invest in a small model table saw or small band saw? (9")  Cut by hand?  (I think my current table saw, miter saw etc. are too large)  What about a small belt/disk sander?

Question group #3:  In cutting gussets and nose block, can I save time by having the pieces laser cut?  or is it easy enough to mill them at home?

Thanks in advance.

Daniel Findling









Daniel Findling
Vintage Aircraft Association MemberHomebuilder or Craftsman
55
Posts
21
#2 Posted: 9/15/2010 11:23:32

Oops.  The full scale ribs measure 49 3/4" not 14 3/4" - I assume from plan shrinkage.




Craig Cantwell
43
Posts
8
#3 Posted: 9/16/2010 09:06:30

Daniel: Paper is notorious for moving around in size due to changes in humidity and moisture content. When I did prints for things where there was a chance that someone would scale off the print, I put a measurement line on the print itself for reference. That way, any copy could be correctly scaled....ie my measurement line was marked off with very exact dimensions for a couple of set lengths...like the scale bars on a map.

In the production world, master templates are either produced  on Mylar or acetate, or also on sheet metal. Mylar doesn't change size like paper does, so when used as a template or master, it's exact for most working conditions. You could get some .020" or thinner Al sheet, or if you can find some big sections of printing plates,and make you a nice master that way.  Or, if you have or know someone that has some type of CAD routing, you could make a drawing with the correct dims and have it plotted on Mylar. As to the coordinates, there are a number of websites that have the ordinate set for the Clark Y airfoil on them. You would just have to multiply the numbers by the correct chord length to be able to create a new plot. I don't have a clue on current cost to plot a drawing to Mylar at some place like Kinko's, as I have my own plotter.

 

As to tools, if you are not comfortable with what you have, there are a number of possibilities. You could change the blade out for a higher tooth count blade on your miter saw and that would be usable for quite a lot of the small cuts. If you want to go human powered, look to a Japanese backsaw to cut the smaller pieces and things like capstrip. Cutting big sections of plywood are going to be either table saw or Skill saw type work, proper blades of course, and spar stock could be done either way.

I've got thousands of cuts on capstrip for one of my projects and I'm going to use my radial arm saw like a chop saw and do all the final cuts with a Lion type mite trimmer. I already have the radial arm saw from ancient project and will simply upgrade the blade as necessary. The next big shop tool for me is a small CNC lathe, as I have about 800 bushings that need to be manufactured for this restoration I'm starting. It's actually going to be cheaper for me to buy the lathe and run it vs having someone run all the bushings.

 

I'm sure that there are people around here that will chime in with other and possibly better suggestions, but over all, keep at it and make the building happen.

 

Craig C.



Joanne Palmer
Young Eagles Pilot or VolunteerHomebuilder or Craftsman
276
Posts
68
#4 Posted: 9/16/2010 11:10:13

One of these saws will do all of this type of work.  http://www.amazon.com/Factory-Reconditioned-Ryobi-ZRSC164VS-16-Inch-Variable/dp/B001HTPSVE  They're  small enough that you can have it right by your side while you build the trusses.

 

Using table saws and band saws is OK but IMO cutting the small pieces on these tools can be dangerous due to the size.  you could use your existing table saw to cut strips of plywood for gussets and small strips of truss member blanks in an assortment of sizes then finsh the needed cuts on the scroll saw.