HS-404 Mounting

[Flying C]

Have been assembling the tail section of my RV-7A and I have a question that I can't seem to find the answer to on the drawings. How does HS-404 mount to the rear spar? There is a notch detail that requires you to trim the piece, but there does not appear to be any detail for drilling mounting holes to attach it to the spar. Does it simply float and only is attached to the skin or am I missing something?

One other question, is there a jig detail for holding the tail section while installing the clecos and riveting?

Thanks,
John

 

[Transporter]

HS-404

HS-404 are nose ribs in the center (both sides of the fuselage opening) of the HS.

The aft end of each HS-404 rib is riveted through the HS-702 front spar and the fwd end of the HS-405 main rib. Should be shown on the left side of the HS drawing (on the RV8 DWG 3 this is shown as "SEC D-D").

The following directions are for the RV8 but should be similar to yours:

"Be sure that the front flange of HS-405, HS-702, HS-810-1,HS-814-1, and the aft flange of HS-404 are pulled up tight. Re-clamp the upper and lower flanges of HS-404 to HS-801PP [skin]. Drill the HS-405 to HS-702 [front spar] to HS-810-1 [reinf angle] or HS-814-1 [splice angle] to HS-404 inboard rib attach holes. Use the holes previously pilot drilled to #40 in the forward flange of HS-405 as a drill guide (see SEC D-D). It is best to use an angle drill for this step but a long drill bit will also work."

I didn't use/feel the need for a jig, just a flat workbench. If you watch the Orndorf DVD he uses a horizontal jig with the HS held upright in the jig...this looked much more difficult that the method in the plans so I went with the plans. YMMV...

Mike

 

[Flying C]

HS-404

I think the mounting for HS-404 is different between the RV-7's and RV-8's. As part of the 7's plans there is a trim detail where HS-404 is actually trimmed so that the face the mounts against HS-702 actually sits inside of HS-710 and HS-714. When I look at detail D-D there are two holes for mounting HS-405 but those holes do not seem to line up with HS-404 due to the trimming that has taken place. Still scratching my head on this one.
Thanks,
John

 

[designerX]

that's a tricky area in my opinion

Sounds awful familiar to the RV-8 plans to me. Were the 405 forward flange holes pre-drilled? Or did you drill them? On the -8 trimming too much off the flange or not drilling the hole in "just the right" spot causes edge distance problems. This area caused me a "do-over" and replacement parts.

Stan

 

[Transporter]

HS-404

The RV8 and RV7 HS are almost identical and use most of the same parts. The only RV8-unique part numbers on the plans are for the reinf. angle and splice angle and skin since the fuselage attach is a bit different for the 8. All of the ribs and spars are the same.

For both aircraft, the HS-404 needs to be trimmed...I followed the full size pattern on the bottom of the plan and had no edge distance issues when drilling the flange holes.

Take another look at SEC D-D. This shows the HS-405 on the left and the HS-404 on the right, with an end view of the forward spar, reinf. angle and splice angles sandwiched in between.

The directions for marking and drilling these parts is in the "Drilling the Horizontal Stabilizer" section:

"Using the dimensions given in SEC D-D, mark the hole locations on the forward side of the forward flange of HS-405. These holes attach HS-405 to the forward spar assembly and HS-404. Make a light mark with a center punch to keep the drill bit from wandering then pilot drill the holes to #40. Note that the upper most attach hole is not centered on HS-810 [RV7 equivalent should be HS-710]. Position this hole as shown to ensure proper edge distance on HS-405."

On my plans the upper hole is 1/4" down from the top of the HS-405 forward flange. The hole will be drilled through the HS-405, the HS702 front spar, and the reinf. angle.

The next hole down is measured 1/4" down from the bottom edge of the reinf. angle and will end up going through the HS-405, the HS 702, and the HS-404.

The third hole down is measured 1/4" up from the upper edge of the splice angle and will also end up going through the HS-405, the HS702, and the HS-404.

The fourth (bottom) hole is measured 1/2" down from the upper edge of the splice angle and will end up going through the HS-405, the HS-702, and the splice angle.

In other words, you should end up with four holes in the HS-405 forward flange. You'll only have two holes in the HS-404 rear flange since the outer portions are cut away.

Hope this helps,
Mike

 

[jmartinez443]

Have been assembling the tail section of my RV-7A and I have a question that I can't seem to find the answer to on the drawings. How does HS-404 mount to the rear spar? There is a notch detail that requires you to trim the piece, but there does not appear to be any detail for drilling mounting holes to attach it to the spar. Does it simply float and only is attached to the skin or am I missing something?

One other question, is there a jig detail for holding the tail section while installing the clecos and riveting?

Thanks,
John

This is on an 8 but I believe the parts are the same:
http://www.rv8alog.com/empennage/hstab/hs4.htm
http://www.rv8alog.com/empennage/hstab/hs7.htm
http://www.rv8alog.com/empennage/hstab/hs9.htm

Be very careful when you drill the holes for the 404's and 405's which have to be match drilled thru the spar. This little hole cost me having to redo my entire HS

 

[Flying C]

HS-404

All,
I want to thank everyone for their help. After reading all the feedback ( and the prints more carefully) I was able to figure things out. Thanks everyone for your help. I am sure more questions will follow.
John

 

[Shockwave]

Confused

I'm on this step, and I just don't see how to accurately transfer the measurements.

Can I mulligan and go 1/4" inch in from the flange edges on HS-405 and HS-404, and then match drill from the nose rib to the main rib once everything is aligned with the skin?