Yet another HS-405/404 drilling question.

[tegwilym]

I've been studying this builder page from "Flyin' Bryan" who seems to have a really nice way of lining up the holes for drilling the 405/404 ribs and spar.
http://bryansrv8project.blogspot.com...1_archive.html

He shows them clamped together so you can get the right amount of edge distance on the tab for the HS-404.
My question about all this....
Would it be safe to simply clamp these together (maybe even straighten the tabs to 90 degrees first) and drill directly through both at the same time? Maybe use the 12" drill bit and go in from the HS-404 front side of the tab? It seems that would be a quick easy way to line up the holes perfectly. If not, drill the holes in one part, separately, then line them up and use the first holes as a guide to drill the next one?

Thanks,

Tom
http://www.mykitlog.com/tomtraci

[KMinor]

I measured/drilled pilot holes on the 404, then used the 12 inch bit to drill front to aft. Just make sure and use a drill stop on the long drill bit, because you'll have a little bend in the bit and when it punches through, the bend might wallow out the hole.

[DaAV8R]

It's been a long time since I've done this. From memory I'm thinking the final hole is a #30. If this is correct, I might suggest you start with #40 pilot holes and then drill up to #30 in assembly. You tend to end up with a cleaner hole and if you should happen to make a small alignment mistake you might be able to move a hole a bit.

[Nihon_Ni]

Originally Posted by tegwilym

My question about all this....
Would it be safe to simply clamp these together (maybe even straighten the tabs to 90 degrees first) and drill directly through both at the same time? http://www.mykitlog.com/tomtraci

No, don't drill through the HS-404 and 405 at this stage. At this step you should just locate the pilot holes in HS-405. Once you have the horizontal stab clecoed together, you'll use those pilot holes in HS-405 to drill through the forward spar, HS702, stiffeners HS810/814 and into the forward rib HS404.

[KMinor]

Originally Posted by Nihon_Ni

No, don't drill through the HS-404 and 405 at this stage. At this step you should just locate the pilot holes in HS-405. Once you have the horizontal stab clecoed together, you'll use those pilot holes in HS-405 to drill through the forward spar, HS702, stiffeners HS810/814 and into the forward rib HS404.

Agreed. I clecoed all parts together, but had my pilot holes in the HS404 and drilled backwards. You get a little better angle for drilling that way because of the angle of the HS and ensure that the edge distance on the 404 is proper. Plus I didn't have one of those cool little skinny drills!

[wirejock]

+1
I did it that way too but used a long #40.

[tweiss]

Tom,

You've got some solid advise on your question from these guys. Prior to building I studied lot's of builder sites myself and was concerned about this area.
When I started laying up parts and pieces prior to cutting and drilling, it started to all make sense in my world.
I think all the above posts really cover the drilling portion to your question.
You mentioned edge distance, so I'll show you what I did to obtain maximum ED on the 404 tabs.

I measured and lightly marked the 404 rear flange tabs for cut out as the plans call for. Then I just set that rib up to the front spar in it's proper location and remarked it so it would just barely fit in between the HS 810 and HS 814.

The photo above doesn't show the light marks that were called out by the plans, but the blue marks which I eyeballed while holding the rib up to the spar gives you much more material (top to bottom) to drill through, and keeps your rivet hole that much farther from the top and bottom edges.

After the rear flange is rough cut to the eyeballed marks, I filed it to size until it fit between the HS 810 & 814.


Once it fits up against the spar, edge finishing deburring.......


Then it's in from the back side


And out through the front side

I would have liked the holes through the HS 810 & 814 to be a little farther from the edges.


But as you can see, it's a give and take between the HS 405 on the back side of the spar, and the HS 810/814 on the front.

Good luck. It wasn't as bad as I made it out to be in my mind when reading all the sites. It just kind of all comes together when you actually have the parts in your hands and begin assembling.

Tom

[tegwilym]

Ah! Thanks for the tips! I like Tom's idea where he just clekoed the ribs and spars together then drilled them all at once. That looks like a good way to do it, then there is no question about if all the holes line up, and if there is the proper amount of material around each hole on the tabs. I've just seen a LOT of people messing up that hole drilling on the 405 flange and having to get a new one.
I think a combination of the clekoing them together, then using a #40 first, then going to the #30 bit to finish the holes. Nice thing is, there isn't a real right/wrong way to do this as long as you get a result that meets the specs!

Thanks, I'll post my results on our build log when I have that part done. :-)

Tom