What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

help with trimming J-Stiffeners

Jwputnam

Well Known Member
Well....I was so proud of myself for finishing the longerons (thank you Larry Buller for fantastic dies!), but then I went to trim the F-786 A,B,C stiffeners and I am lost. The directions are less than intelligible as I know many of you have discovered before me, but in searching the forum I have found very little in the way of explanation that this dummy can follow.

I realize that each of the three sets has a left and a right and I get that, but when it comes to trimming the opposite ends, the angle will not come out parallel to the those ends if I follow the pattern on DWG18 exactly. I ASSUME that the angle is there to meet the bulkheads flush and exists because the stiffeners are angling back from wider bulkheads to narrower bulkheads. For that reason, the angles at both ends should be parallel to each other (one would think).....correct? BUT, if I cut them so that they are parallel, they wont match the drawing schematic.

Soo....either I am misinterpreting the necessity to cut exactly to the drawing or I am screwing up the whole exercise.

My guess is that some of you are laughing. I deserve it, but I sure wish that the plans were written for pre-teens!

Thanks!
 
The note on Dwg 18 (D10) says, "Note: Trim to fit all F-786 stringers. Fore and aft end conditions vary depending on the bulkhead. For best fit, note the angle between stringer and bulkhead and trim accordingly."

In basic terms, trim to fit. The "x" dimensions on the drawing are a rough guide, that's all. Ensure good edge distance for the fasteners on the ends and you're all set.
 
Thank you. I guess that I will cut the angles parallel then, but I am thinking that I will until I get the fuselage all clecoed together and then draw the cuts out. Maybe just cut the forward ends ahead of time.

I have learned to be afraid of cutting and drilling, so I am now very tentative!
 
Stiffeners

John
I detailed the cut in my blog. Fuse page.
They are confusing but once you put one in place, the end shape will make sense.
The7 stiffeners should be very similar to the 9.
I do recommend cutting them a 1" too long first. Then cut them to fit the forward end. The extra gives you some margin for error in case you get and end cut or shape wrong.
Finally, when you insert them into place, mark and cut the aft end to fit.
Here's a post that may help.
http://www.vansairforce.com/community/showpost.php?p=968518&postcount=32
 
Last edited:
I'll check out your site for sure, but I am afraid that I already cut the six stiffeners to the prescribed length. I think that trimming the forward ends makes sense and then trimming the aft ends when I pre-install them.
 
Larry,

Thanks so much. I was making some false assumptions. Now that I see your photos, I realize how they fit in. The angle that I was referring to does not need to be flush with bulkhead, it only needs to be clear of contacting it.

I have trimmed the aft ends of the short upper pieces and I will trim the aft ends of the other 2 longer sets tomorrow before I prime them all and begin to set up the fuselage. I will then wait to trim the forward ends when I begin staging the construction. I hope that they will be long enough. As I said, I cut them to the prescribed length already.

Thank you for the clarification........and I agree that Vans could be more clear and make the build considerably "easier" and maybe sell more kits that way, but over all, they have done a superb job. I built a Factory Five Cobra and a small wooden boat from blueprints and I have experienced even worse by far! Still, I would love to have been building during all of the many hours that I have spent trying to interpret these plans or remaking "gotcha" parts at great expense.

YOU ARE THE BEST!!!!!
 
Back
Top