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JG3

Elevator Hinge Reinforcement

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To be fair, I think he is really building it, not assembling a 701 kit.

M...well, I can see where that might cause one's mind to sideslip occasionally???

 

 

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Nope, my filthy mind predated my scratch building. (Although I do agree, it tends to add to the insanity.)

 

Be fair though, you can't come out with a quote like that and expect people not to snigger a little.

 

 

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Nope, my filthy mind predated my scratch building. (Although I do agree, it tends to add to the insanity.)

Be fair though, you can't come out with a quote like that and expect people not to snigger a little.

M....there's certainly no telling what will get a rise out of some people?

 

 

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Always checked mine on a pre-flight. Only recently discovered 1 rivet head missing. There were no signs of any fretting or movement.

 

The Early savannas like mine, used countersunk rivets and domed them with the riveter. This probably weakens the head of the rivet.

 

I Replaced them ALL with domed avex rivets, and just keep an eye on them.

 

 

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Always checked mine on a pre-flight. Only recently discovered 1 rivet head missing. There were no signs of any fretting or movement.The Early savannas like mine, used countersunk rivets and domed them with the riveter. This probably weakens the head of the rivet.

 

I Replaced them ALL with domed avex rivets, and just keep an eye on them.

The Zenith 601xlb/650 supplied kits, all the rivets are countersunk [avex] and the supplied nose die is ground so you end up with a shallow domed finished head. This work hardens the rivet head to give it extra strength and to date I'm not aware of any issues with this method of construction. Cheers

 

 

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The Zenith 601xlb/650 supplied kits, all the rivets are countersunk [avex] and the supplied nose die is ground so you end up with a shallow domed finished head. This work hardens the rivet head to give it extra strength and to date I'm not aware of any issues with this method of construction. Cheers

That's the method I use too. Actually sent my riveter dies off to Zenith and they ground them for me. The literature on their site also states that it makes the rivet hold tighter than would a standard domed head.

 

 

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Any final solution to this topic?

 

Mirroring part 025 seams a good idea.

 

On the other handside, if all other parts around are fine, then this would be just to much and a simple M4 ore M5 bolt instead of the outermost rivet would do as well.

 

So, what to do?

 

 

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Awhile ago Bill Grieve mentioned that someone had noticed a missing rivet head on the Elevator Hinge Reinforcement, part # SD025, and a couple of other aircraft were found with the black stains around the rivet heads that indicates movement.... I checked my aircraft and found all three rivet heads missing altogether, allowing the elevator to wobble sideways about 20mm! The purpose of that bracket is precisely to stop sideways movement of the elevator. The movement didn't show up in pre-flights because I just worked the elevator up and down for free movement but didn't push-pull sideways....

[ATTACH=full]43704[/ATTACH]

 

You can see those rivets by peering upward from under the right side of the elevator. There are three rivets in a horizontal row. It wasn't difficult to replace the rivets. Just needed to cut away a small tab of the skin on the underside of the elevator, and needed a close fit right-angle drill to drill out the old rivet cores. Then could just reach in with a slim model riveter. I used 3/16" stainless rivets time, and will be keeping a close watch on them and their supporting structure.

 

Can't figure how those rivets could have felt the stress needed to break them..... But also checked a Zenith 701, which is identical construction, and found one rivet sheared, so it's a common issue. Everyone with Savannah and 701 aircraft need to keep a close eye on those rivets..... I don't know if anyone has informed ICP yet, but there should be an AD in that regard.

 

JG

Hi JG

 

I have always been under the understanding of not using stainless steel rivets for attaching aluminium due to the noble metals scale, electrolysis and its effect that the aluminium will waste away. I am not an expert in this area and have not built a Savannah and don't know what the material structure components are where you have used the s/s rivets to replace broken rivets. My comment is meant to assist and I'm keen to kow if my comment is correct or wrong. Maybe Reg B or a Tech person on this forum could advise about my comment. Best regards Mike

 

 

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Hi JG

I have always been under the understanding of not using stainless steel rivets for attaching aluminium due to the noble metals scale, electrolysis and its effect that the aluminium will waste away.

Can't argue with the science, but in the real world within reasonable time periods it just doesn't happen.

 

Homebuilt race cars I have pulled apart from the 60's and 70's sometimes have a large amount of powdery oxidation between the aluminium panels, but no problems that I have seen around the rivet holes. Better prepared ones, eg; fully painted panels, seem to have no problem at all.

 

 

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Hey BlueAdv..

 

Sonex airframes are built primarilly with 6061 alloy, held together with 10000+ stainless pulled rivets in close formation.

 

The factory say 6061 doesn't corrode and don't recommend any corrosion treatments, which is crap. Mine is primed internally with etch primer along all mating surfaces.

 

Some guys go the alodine + primer route, I valued my life expectancy over airframe lifetime.

 

On the exterior of my polished example it exibits corrosion around surface rivet heads on/under wings, under the fuse, around the tail, primarily where dust, exhaust residue and moisture have accumulated.

 

Keeping dust and moisture at bay is key to controlling the galvanic process.

 

I keep it under control with regular cleaning and polishing to remove fine dust and the white cancer.

 

Enduring winters in a carpeted hangar is the worst environment for it.

 

I'm also paranoid about getting it wet in rain as there are all those open rivets and seamed panel pathways into the airframe!

 

 

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Hi Tony, I etch primed all mated surfaces and of course the plane is painted and lives in the hangar. Will be interesting to see how it goes given the salt environment down here

 

Peter

 

 

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Still don't now what to do.

 

1. copying SD 025

 

2. use stronger rivets or bolts

 

3. do nothing

 

 

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Hi JG

I have always been under the understanding of not using stainless steel rivets for attaching aluminium due to the noble metals scale, electrolysis and its effect that the aluminium will waste away. Best regards Mike

Yeah I'm well aware of that issue and certainly wouldn't use s/s with Al in a marine environment. But I've seen the results of s/s rivets in aluminium aircraft for many years with no problem, that I decided to use them here where they are easily inspected daily.

 

JG

 

 

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Still don't now what to do.1. copying SD 025

 

2. use stronger rivets or bolts

 

3. do nothing

If you can access to put a couple of bolts in there, that would be a good solution.

 

JG

 

 

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To shear rivets like that you must have end float and some shudder type sideways force being applied. Landing on a sealed surface maybe? Nev

 

 

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Some interesting pieces of advice in here!

 

 

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Still don't now what to do.1. copying SD 025

 

2. use stronger rivets or bolts

 

3. do nothing

Did number 4. and installed two extra rivets at the end of SD 025 where the stress is supposed to be greatest.

 

 

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Thank you, JG. I will make that mod before assembly.

Are there any other bushes I should be looking at while I'm doing that?

 

Aileron bushes in particular. For those I made the bush with an outswide diameter of 10mm and drilled out the holes in the ailerons to 10mm, then bolted the bush tight to the support bracket. So that the aileron bracket rotates on the outside of the bush, giving a much larger bearing surface of aluminium on teflon, rather than the small area of brass on steel. Haven't shown any wear in many hundreds of hours.

Do you have any pictures to illustrate this, JG?

 

 

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Do you have any pictures to illustrate this, JG?

I don't have any photos but will try to do some on Sunday....

 

 

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541164B4-4A07-4B02-9A17-607232C751C6.jpeg.c376970a4266d47e8bb249951056e842.jpeg I was looking at my elevator hinges and noticed that looks to be slightly smaller in diameter where they have drilled the hole for that split pin. Should I be concerned with this, to me it looks like a potential failure point on a critical flight control?

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The point where the splitpin hole is drilled has no load, the load is inboard of that point, the nut is only a retainer for the bush. The highest shear load is where the pin is welded to the flange, if there is no sign of cracking or bending there then the fitting is safe.

 

 

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Three hinges on a door is always a problem, as the door warps the centre hinge always becomes loose, the elevator hinges on the Sav probably suffer misalignment under load. ICP should offer a repair method if this is a problem on high hour aircraft.

 

 

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Posted (edited)

Did number 4. and installed two extra rivets at the end of SD 025 where the stress is supposed to be greatest.

 

I have had an operation and while recovering I decided to read through anything to do with the horizontal stabiliser (which is nearly complete) and the elevator. I had quite a think about this issue and decided to do No 5 which is a small bracket which braces the centre in the opposite direction. The idea is for this bracket to be a "helper" to the bracket on the other side supplied by ICP. I was able to keep this bracket to just 6 grams.

 

Unfortunately I am too weak (at present) to do any more than about an hour's work in my shed: just enough time to make the bracket and rivet it in place. When I next get back to it, I may also do Major Tom's No 4. :-)

 

162761849_ElevatorHingeextrabracketC.thumb.jpg.26aa00f0a9bab72955c42f47098380f6.jpg

1853818103_ElevatorHingeextrabracketA.thumb.jpg.2611c166d025612de431f777e5bf809b.jpg

1824853768_ElevatorHingeextrabracketB.thumb.jpg.3c02c8845b1b79fd726322a310e7ac7b.jpg

Edited by Guest

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