SB 14-01-31; RV-6, 7, 8

[Ironflight]

Originally Posted by David-aviator

So far there are no reports of a crack where the slot is absent, at least not that I have read.

I know of at least one that was reported - not sure if it is on this thread though.

That's the problem with a long thread like this - it's very hard to capture it all.

[SilverEagle2]

Now that I have caught up on all the posts and info, perhaps I can offer some reasoning for the notches being or not being present between the models.

The -7 and -8 share many of the same parts but the fuselage at the HS is not the same shape. The 7 is obviously wider and the skins are of a different profile at the HS root. These differences can be accounted for in either stamping different spars or having the builder modify them to suit. Van's clearly chose the latter.



As you can see in the DWG 3 snippet, you must modify the part formed for the -8 to meet the needs of the -7. At the same time, the notches are called out to remove the radius portion of the spar after the flange is removed.

I looked at my HS and I did a decent job of radiusing the notches, but I will be complying with the SB as it is WAY easier to do it off the plane and be worry free. I don't like the idea of undoing work...but who does.

I presume that the -6 may not have notches because that part was made to match the plans.

If I am up in the night, let me know. However, I think that is why many do not have the notches in the -8s and -6s.

[Mark Burns]

For those that might be wondering the kit is $15
I knew they would be fair but this is just plain nice.

Mark

[BillL]

Originally Posted by DanH

Doesn't work well with sheet aluminum. The result is a warped sheet.

re: -shot peening (glass bead blast)

I was thinking just the edge of the sheet, not the flat sides, so yes it could warp but some compressive is better than none. The affected depth is only along the order of the sheet thickness anyway. It could work well for the stress concentrated area.

It might delay the crack initiation, but granted that even if it worked, it would be a super pain to keep beads from the spaces in the structure.

[Hum]

Just spoke to Bruce at Vans, at present SB parts will take around a week to ship..

[JonJay]

Originally Posted by Sheldon

Inspected mine yesterday.. Dye Penetrate test..No cracks!
707 hrs RV6A 180 hp no acro no grass strips.
Smooth edge dressing to keep from having stress risers probably is the key. Even samples with relief notches, (done correctly or otherwise) have cracks..

I'll keep inspecting.. But there has to be an easier fix...??

I will probably get flamed for this, but....
If the crack did not progress under the flange, some I have seen here have not, I would wedge some backing material under the sheet, stop drill, and dress the hole as best I could. I would then re-inspect on some reasonable interval to see if the crack propagates beyond the stop drill. It takes ten minutes to pull that fairing and check. If the crack did not propagate, it becomes an annual inspection per the SB.
I do not feel the is an emergency as Paul and others noted, no tail planes are flying off....
That is just me. I would not recommend this to anyone else!

[HSANTIBANEZ]

I think i will inspect and if no crack i will also build a forward horizontal completle new with the reinforcements, what could be the cost of that? in time and money? i think the work is too much risky than the crack is in a future crack in a bad re-riveting.

if all the empenage was about USD 1.800 the half without elevators could be USD800?

[catmandu]

1995 RV6A
309 Hours
O-320
FP Sensenich
Occasional Rolls
Mostly Hard Surface
Very small notches
No Cracks

[Andy Hill]

RV-8 DWG 3 7/20/01

HS-702 distance to bend is 4 7/16". From above the RV-7 is 5 3/16" and asking for the flanges to be trimmed to the "Bend Line" and notches added.

Given the 6deg sweep at the Bend Line:

1. I would think "built in stress" is related to the exact distance from the end of the bend to the flange start
2. The plans/manual are not clear that this could be critical
3. Whilst the plans call for a min radius of 1/8", the Build Manual technique advocates "blocks of wood / hand seamer / hit with a mallet" which is somewhat imprecise
4. HS-810/814 angles also have to be similarly (crudely) bent

My guess (and more than happy to be corrected) is that vulnerability to cracking is down to how the bend line relates to the flange starting point, and how well the HS-810/814 bends match the HS-702 bend. These parts are after all, now firmly riveted together.

Maybe it ought also be borne in mind that these instruction are at the end of the 1st page of building - new builders are still feeling their way at this stage

The SB is not clear as to the implications of the crack, my instinct says it will be fairly self limiting, running into a hole, or losing the stress to further crack. I cannot think much load is on the thin spar part at this point, given the substantial angles riveted to HS-702 top and bottom for some distance each way. Those people who choose to do the full SB, it would be interesting to photograph how far the cracks progress?

The SB is a "belt and braces" solution to cope with the cracks. Even for those without cracks, incorporating the SB might not do anything to prevent cracks, it just means you can fly on with them.

I would think longer term Vans will supply a new HS design, or at least improved instructions, to prevent the cracks. For those looking to a long term / new HS solution, I think waiting a while might be better than rushing to order / build a new one incorporating the SB.

Just my 2cs worth

[PerfTech]

.... We inspected 3 airplanes on our field, 1-8 & 2 7s. We found cracks on two of them. The 8 was the most obvious and easiest to spot. As another member stated a few posts back, I am curious about the nine and why it seems excluded from this issue. Thanks, Allan..