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Empennage Front Spar Bends

Mort04

Member
Hey Guys,

Im diving into the front spar of my Empennage. Attached is a link to some pictures of the HS-702 spar channels with the relief holes. Is the edge distance sufficient? The measurement is in the inch setting, so as you can see in the picture its shy of .25in or 1/4 of an in. It also seems like the actual bends on HS-710 and HS-714 don't completely match up with the bend in the doublers. So in short, everything appears to be bent at 6 degrees, just a bit off from one another.

https://www.flickr.com/gp/158887686@N05/5Q5qi6
 
Looks good to me, min edge distance on the milspec looks like .219 from center of rivet. Therefore if you add the radius of the rivet here to your .208 you are well within spec at .2705. Someone else will probably chime in to verify my interpretation of the mil spec.

https://www.vansaircraft.com/public/Specs.htm
 
Mil spec

Jereme is correct on his read of Mil Spec. The rule of thumb is 2X Diameter of the fastener, measured from the center of the hole to the edge.

I see this come up often and Vans really should mention it in the manual.
When the hole is drilled for the relief notch, start with a punch mark at the vertex of the bend. Not sure if that's where you started. The hole should be drilled in the bend, 45 degrees from the web and flange. Then drill in increments but not to the full 1/4". You can always remove more.

It's hard to tell in the photo if the bends of the parts are in the correct place and degree. Pretty minor fit issue. The F714 and F710 bars need to match as far as the location and degree of the bends.

Also, don't make the relief cuts at the ends of the two F710 and F714 angles until after the holes have been drilled. That way you control the edge distance with the relief cuts and rounding of the ends.
 
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It's hard to tell in the photo if the bends of the parts are in the correct place and degree. Pretty minor fit issue. The F714 and F710 bars need to match as far as the location and degree of the bends.

Also, don't make the relief cuts at the ends of the two F710 and F714 angles until after the holes have been drilled. That way you control the edge distance with the relief cuts and rounding of the ends.

Thanks for the input! I might be misunderstanding what you mean by relief cuts. Are you talking about the tapering and rounding of the ends on the 710 and 714 as releif cuts? Or do I need to drill a relief hole at the bend line on 710 like the 714 angle has on it? I?ve already tapered and rounded the ends and just ran out to the garage to measure the edge distance. It should be good on all the holes.
 
Relief cuts

Thanks for the input! I might be misunderstanding what you mean by relief cuts. Are you talking about the tapering and rounding of the ends on the 710 and 714 as releif cuts? Or do I need to drill a relief hole at the bend line on 710 like the 714 angle has on it? I?ve already tapered and rounded the ends and just ran out to the garage to measure the edge distance. It should be good on all the holes.

Yes, the ends of F710 and F714 and many other parts moving forward are cut to a taper and rounded. I messed more than one up by cutting then rounding before the hole was drilled and ended up making new. Much easier to drill first then draw an edge distance circle and cut. You're good. Sorry if I scared you. Build on.
 
Yes, the ends of F710 and F714 and many other parts moving forward are cut to a taper and rounded. I messed more than one up by cutting then rounding before the hole was drilled and ended up making new. Much easier to drill first then draw an edge distance circle and cut. You're good. Sorry if I scared you. Build on.

Thanks! I think I have a handle on everything now. Couple more days off from work so I am hoping to make some good progress.

On a side note, nice blog! Yours as well as a couple others I studied up on before I ordered my Kit. I clicked on it today, not knowing it was you who replied. :)

Again thanks for clearing up my questions.
 
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