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Skybolt Fasteners - Installation

Phil

Phil

Well Known Member
Anyone have a site that profiles the installation of Skybolt's fasteners on the cowling? The documentation doesn't really talk about the 10 installation which is completely different from the installation they have documented for the two place model.

There's some tricks with regards to layout that I'm not fully grasping.

Any help would be appreciated.

Thanks,
Phil
 
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Phil,
I tried to do the installation and actually riveted them to the firewall. Unfortunately they would not work without modifying the cowling. I believe it is due to the grey cowling that came with my kit. The honeycomb portion of the cowling extends too far to,the aft edge of the cowl, which would not allow the sky bolt triangular brackets to lay flat on the inside surface of the cowl. I spoke with someone who spoke with the designer of the bracket, who suggested I grind down the entire rear edge of the cowl to remove the honeycomb. This would allow the brackets to lay flat on the inside of the cowl. I chose not to do that and returned the items to skybolt and went with the factory hinges.
Having said all of that, now that the hinges are installed, I can see it would be a lot easier to remove the cowl with the skybolt fasteners. So before you rivet them on, you might want to take a look at your cowl fabrication.
 
fasteners

You can bend the skybolt fastener tabs somewhat to match the cowl angle. Working on a -6, that was necessary and ended up working well.
 
Thanks Bill.

I have the same gray cowl and I never thought about the interference between the honeycomb and the tabs. That's good to watch for.

Good tip.
Phil
 
Phil,
Here's the link to the instructions for installing the MILSPEC Camloc kit on RV's: http://www.milspecproducts.com/instructionsindex.htm
I know they're not Skybolt, but you might find it helpful nonetheless. Besides having to adjust the width of your mounting tabs (or relieving the honeycomb) to eliminate interference, don't forget that you might need to shim between the tabs and the firewall flange to get the right depth so the that the cowl will sit flush to to the fuse skins. I'm planning on .020 shims just like the plans call for when using hinges.
 
I'm planning on shimming to .032 and then adding a couple of layers of 9oz cloth to the inside of the cowling as required to bring it back flush to the deck of the upper fuselage. That will accomplish a perfect fit because I can sand down into the added layers as (if) needed.

But it should net out around .020. It'll just be stronger around the attach points and also less likely to balloon out in flight.

Phil
 
Phil said:
It'll just be stronger around the attach points and also less likely to balloon out in flight.
Click to expand...

Good plan Phil. Bowing between fasteners is the one gotcha with 1/4 turns, so added glass thickness is a plus. Next time I'll probably run a two-ply carbon strip on the inside and outside for stiffness.

No joke....pressures ballooning the cowl can be over 100 lbs per sq ft.

BTW, if I had to choose between hinges and reworking the edge of the core for flange clearance w 1/4 turns, bring on the grinder!
 
Good to know Dan. Thanks.

I was thinking of a 3" carbon strip too that runs parallel to the scallops. Most likely it would be laying on top of the honeycomb, but that's fine. I think a couple of strips of carbon fiber would eliminate any chances of ballooning.

They have some at the local West Marine, but it would require removing half the money from my son's college fund. So I'm probably going to add some on to my next order from Spruce.

Phil
 
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Holes

Make sure you drill 15/32 holes. Not 1/2"
Like the instructions say " if you don't have a 15/32 step drill. "
If you don't have a 15/32 step drill, drill a smaller diameter with
Your step drill and finish off with a 15/32 twist drill. 1/2" allows
To much play in the 1/4 turn screw. Only an issue with
The non floating fasteners.
 
I've considered converting my piano hinge to skybolt.
I'm just finishing up my 7A to 7 conversion and unfortunately, I have to trim my cowling back about 1/2".
This is my final task. It would probably be easier to trim and attach the skybolt fasteners versus relocating the hinge back and realigning.
 
I made the first cut on the aft edge of the top tonight and can confirm that I'll be into the honeycomb by ~1 inch. So it will require a modification of the core.

Once I get the fit a bit closer, I'll be able to tell you exactly how far and I'll share how I went through the modifications.

For those following along from home, I'm still on Vans plans and currently completing Step 5 on page 47-5. (That kinda reminds me of the old Captain Kangaroo. If you've got the papers, follow along at home! :))
 
DanH said:
Good plan Phil. Bowing between fasteners is the one gotcha with 1/4 turns, so added glass thickness is a plus. Next time I'll probably run a two-ply carbon strip on the inside and outside for stiffness.

No joke....pressures ballooning the cowl can be over 100 lbs per sq ft.

BTW, if I had to choose between hinges and reworking the edge of the core for flange clearance w 1/4 turns, bring on the grinder!
Click to expand...

Which is 0.69psi

I am using the Milspec fasteners. I have just riveted on the flanges. Now you've got me worried. I have the grey cowl. I won't know if it all fits until mount the engine and start trimming the cowl.
 
You can get a strip of carbon fiber tape and run it parallel to the tabs. That'll keep it from bowing out.

I picked up 12' of this today, but I think I'm going to need another 12' to do all the edges of the cowling.

http://www.aircraftspruce.com/catalog/cmpages/unidirectiontapes.php
  • Right and Left sides of the upper cowl.
  • Aft edge of the upper cowl.
  • Right and Left sides of the lower cowl.
  • Right and Left Aft Edge of lower cowl.
I'm pretty sure that's more than 12'. But I'll wait and see before I buy another roll. $$$

Unidirectional glass would be fine too, but I just like the rigidity of carbon here because it for sure won't bow.



Phil
 
Phil said:
You can get a strip of carbon fiber tape and run it parallel to the tabs. That'll keep it from bowing out.
Click to expand...

...if you run a strip on both the inside and the outside of the cowl, with the existing glass as a core. Adding carbon to just the inside would be a poor utilization of material property.

Unidirectional glass would be fine too, but I just like the rigidity of carbon here because it for sure won't bow.
Click to expand...

Roughly 3, maybe 4 times more rigid.
 
DanH said:
...if you run a strip on both the inside and the outside of the cowl, with the existing glass as a core. Adding carbon to just the inside would be a poor utilization of material property.
Click to expand...

Hmm. I was thinking of running it on the inside only. I'm not sure I could run in externally and get it to blend in. I might be able to remove the honeycomb core and that's probably overkill and a lot of extra work for little return when I could just lay down a couple of extra layers of 9oz cloth as shim.

Phil
 
Running strips on the inside will make the task of cutting into the honeycomb less intrusive, as the brackets will sit lower inside the cowl..
 
Interference.....

I got the top trimmed today. Here is the interference Bill warned us of. Looks like 1/4" approximately. I'll likely remove .75-1.0" assuming the rest of the cowling measures out the same.

More to follow. I'll keep you posted.

545152_3717467709187_1650597149_2990567_1825101484_n.jpg
 
Phil,

I used milspec fasteners on the firewall edge of the upper cowl of my -10, but did not add any layers of fiberglass or carbon fiber. In flight I do get about 1/8" of bulging right at the midline of the cowl; none elsewhere. If I was doing it again I would add another fastener closer to the centerline. I don't think you will need much reinforcement to eliminate the bulging.

Jim Berry
Rv-10
 
After looking at the photo closer, I think I might change my plans with regards to removing a 1" band of core material on the aft end of the cowling. Instead I think I'm going to only remove the areas of interference. It will be less intrusive and create a small recess around the tabs.

The idea is that those recesses will guide the cowling into the perfect position around the tabs. It would essentially lock in the perfect position for the fasteners to be aligned.

Might be a crazy idea, but it doesn't sound that unreasonable. It's probably less work than removing a 1" band and then repairing it all the way around the cowl.

Does that sound more user friendly from an on-and-off perspective? Or could I be setting myself up for a frustrating experience getting it on and off?

Phil
 
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Phil said:
Instead I think I'm going to only remove the areas of interference.
The idea is that those recesses will guide the cowling into the perfect position around the tabs. It would essentially lock in the perfect position for the fasteners to be aligned.


Phil
Click to expand...

Phil,

I think your idea is a good one. Remove only what is necessary. As far as alignment, you will find that the milspecs will do a very nice job of pulling the cowl into alignment.

I had the green cowl, A real pos to start with, but with enough beer and sweat it submitted to my will. In your photo it looks like the flange projects further forward than mine. I will measure mine when I am at the hangar tomorrow. It may be just an optical delusion.

Jim Berry
RV-10
 
Phil,
Would it not work to just shorten the flange by a 1/4" or so? That would have been my first inclination.


Shannon
 
You really don't want to shorten the firewall side of the bracket. That was my first inclination when I installed them. The issue is, it removes the flat surface edge that contacts and supports the cowling around the entire aft edge.

Here are my photos of the install before I removed it....

IMG_2289.jpg

IMG_2290.jpg

IMG_2287.jpg


I would not use the fasteners along the side or the bottom. The hinge works great, looks good and is a ton easier to install on the sides. I did not install the hinge on the bottom, I fabricated a small strip of 060. and used nutplates and #8 screws.
 
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Phil said:
For the record, the tabs with the Skybolt kit are 1 7/8" wide.

Phil
Click to expand...

Wow! Judging from the pictures above and how close the spacing is, I can't believe that bowing in flight would be an issue, even without the addition of FG or CF reinforcing strips. Phil, are you trying to use less of them (bolt points) across the edge? Is that why you're wanting to strengthen the edge?
 
ppilotmike said:
Wow! Judging from the pictures above and how close the spacing is, I can't believe that bowing in flight would be an issue, even without the addition of FG or CF reinforcing strips. Phil, are you trying to use less of them (bolt points) across the edge? Is that why you're wanting to strengthen the edge?
Click to expand...

1 7/8" is the depth from the firewall to the forward end of the tab.

The spacing of the fasteners is 3.5". But even at that, the cowling will balloon out between the fasteners at 200mph. Hinges are continuous fasteners, so they don't balloon nearly as much. The fasteners focus all the forces at the attach points.

The reinforcement makes the cowling more ridged so you get less bowing.
 
Phil said:
1 7/8" is the depth from the firewall to the forward end of the tab.

The spacing of the fasteners is 3.5". But even at that, the cowling will balloon out between the fasteners at 200mph. Hinges are continuous fasteners, so they don't balloon nearly as much. The fasteners focus all the forces at the attach points.

The reinforcement makes the cowling more ridged so you get less bowing.
Click to expand...

Phil,

My mounting flange is 2" at its widest and the milspec fasteners are centered 1 3/8" forward of the firewall, on 5" centers. As I mentioned before, the only place I have any ballooning (@170k cruise) is the upper cowl midline. The green cowl honeycomb stops 2.5" forward of the firewall. I did not add any extra layers to the aft edge of the upper cowl.

I would be very surprised if you get any ballooning using 3.5" centers. It is probably overkill, but since the mounting flange is already riveted in place, I would just go with it.

Jim Berry
RV-10
 
I think you're right. Especially with the close proximity of the honeycomb core.
 
What is the conclusion?

So, Phil....what was the conclusion to your story? I am considering installation of the skybolts for the upper firewall area...but see your dilemma. Can you give us some thoughts on how to proceed?

Thanks,
David
 
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