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  #1  
Old 08-23-2012, 12:00 PM
goldbar goldbar is offline
 
Join Date: Apr 2010
Location: slc, UT
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Default Longeron template (F-718 template and F-721 don't match)

So the answer must already be hidden in here somewhere, but it is not jumping out at me..
So the template for bending the longerons labeled "F-718-l and F-718-r bending template" and the curve of the F-721B-L (and R) do not match ? Huh ? Not the solid line or the dashed line, what am I missing here ? I have the bend nearly complete to the template but in looking ahead at the next step I pulled out the canopy decks (F-712L & R) and lo and behold, they differ by about 1/4" or more (eyeing it).
This has to be some misunderstanding on my part ?
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Old 08-23-2012, 12:06 PM
Flying Scotsman Flying Scotsman is offline
 
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Just a question...did you use the original drawing, or did you make a copy of it to cut up? I did the latter, using a large-scale scanner at Kinko's, *but* I held the two up together to make sure the scanner/printer did a perfect 1:1 copy.

If you made a copy and it wasn't exactly 1:1, might that be the cause?
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  #3  
Old 08-23-2012, 12:22 PM
goldbar goldbar is offline
 
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I cut the original off of DWG-17, the length matchs perfectly ?
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Old 08-23-2012, 12:32 PM
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N9331v N9331v is offline
 
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I did the same as goldbar
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  #5  
Old 08-23-2012, 01:00 PM
krw5927 krw5927 is offline
 
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Make sure you're reading the drawing carefully. I almost had the same problem on my 9A (longerons are the same) until I realized I was not aligning the canopy decks with the longerons correctly. Once I realized my mistake it turned out the longeron template made a perfect part.
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  #6  
Old 08-23-2012, 02:50 PM
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From what others have said, the older kits had a "Not to scale drawing". You will need to match the F-721-B not the drawing.
I have a newer kit and mine was scaled perfect. I got so wrapped up in what others had said that I goofed and drilled my F-721-B in assembly in the wrong place. I had to by another longeron.
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  #7  
Old 08-23-2012, 03:42 PM
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swisseagle swisseagle is offline
 
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Default Do not take the plan as guide!

Hello,

As Ken Krueger told me once, do not take the plan as a guide to bent the longeron! The plan is printet on paper and the paper grow or shrinks depending on humidity, temperature and age.

Take the aft canopy deck F-721B as template, those two parts have to fit together. Maybe start with the paper template, but finish it with the aft canopy deck.

You can also check with the aft canopy deck, if the plane is accurate or streched.

Regards, Dominik
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  #8  
Old 08-23-2012, 07:56 PM
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RV7AJeremy RV7AJeremy is offline
 
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Default check the start of bend locations

Just bent mine last weekend, its a perfect match. Double check where you are placing the fwd/beginning of F-721B. It starts at 28-1/4 but the bend doesn't start till 38-7/16.
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  #9  
Old 08-23-2012, 10:08 PM
goldbar goldbar is offline
 
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Thank you all for your posts.. It makes perfect sense to match the bend to the F-721, it jast had me concerned that the 721 and template were not the same, I'll finish my bends with the 721.. I appreciate all of your comments and help.
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  #10  
Old 08-24-2012, 11:04 AM
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rzbill rzbill is offline
 
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Sorry but I'm not convinced that real comprehension has occured yet, Goldbar.
No insult intended. I remember looking at it incorrectly in the beginning too.

The curve shown on the plans only PARTIALLY resides within the 721 deck as Jeremy and another said. See dwg 18

Certainly, you can use 721 as the final arbiter of shape, but make SURE you have it located on the longeron in the correct spot before "correcting" the curve.

My template on dwg 17 and and the 721 placed per dwg 18 matched spot on.
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Last edited by rzbill : 08-24-2012 at 02:10 PM.
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