Skybolt installation question

I have the flanges installed and it is now time to rivet the firewall receptacles. I was under the impression that skybolts were adjustable meaning that the inner part of the receptacle could move around a little after riveting until you had them right where you wanted them then lock them in place. I riveted in my first receptacle and the shop head on the rivet holds the inner part of the receptacle tight. There is no adjustment at all. In the instructions they mention a floating receptacle. Is that the kind that moves a little? Should I be concerned or just start riveting away?

skybolt

In the skybolt kit, there are only a couple of floating receptacles. All of the others are FIXED, hence accurate placement and drilling is required.

I used the drill inserts for mine and it worked out great...no need for any floating receptacles.

If you need the floaters, contact skybolt. The floaters move...a little...

Even with the fixed receptacles the cowl will move around a little bit. I would not recommend the floaters.

In my Skybolt kit I received 6 of the floating receptacles and the rest were fixed. The kit was only for the firewall The cowl split line was not included. I installed 2 floaters on each side at the bottom of the top cowl (the curved area). All along the top in between all are fixed. I used the Vans hinge on the bottom cowl sides and 6 fixed Skybolts along the bottom. This makes installing and removing the cowls easy. In the instructions it mentioned that the floaters on the side make it easier to install and remove the cowl. After talking to a few other RV builders I left a 3/8" gap between the spinner and the front of the cowl to make it easier to get the bottom cowl on and off. Seems to work ok for my 7.

Al

I wanted all the fixed that were possible to more rigidly holding the cowl. Lots of forces on that cowl.

Here is a few posts related to how I got the precision. It worked quite well until I had to remove the forward skin and it was a trial of readjustment afterward.

http://www.vansairforce.com/community/showthread.php?p=894620&highlight=skybolt+alignment#post894620

rocketbob said:

Even with the fixed receptacles the cowl will move around a little bit. I would not recommend the floaters.

Click to expand...

+1

Spacing

I used this thread for spacing and used three "floating" receptacles at the curved section of the cowling.

http://www.vansairforce.com/community/showthread.php?t=74619&highlight=skybolt+installation

Floaters

I recommend floating skybolts all way around. What you have is -162 fasteners. You want the -161. One riveted you?ll have a small amount of adjustment which is required. Same price and they?ll swap them out no problems

I've got them installed on the lower cowl and now powder coating the upper cowl flanges. Tomorrow will hopefully get the upper ones in then can start on the seam fasteners. Pretty happy with how the lower cowl ones look and fit. I've never done this before so not really sure how good it really is. Hoping when I get them in and remove my alignment spacers the cowl still fits well.

dwranda said:

I was under the impression that skybolts were adjustable meaning that the inner part of the receptacle could move around a little after riveting until you had them right where you wanted them then lock them in place.

Click to expand...

With either fixed or floating receptacles, the core screws in and out for depth adjustment. There is no lateral adjustment which can be locked after installation.

I riveted in my first receptacle and the shop head on the rivet holds the inner part of the receptacle tight.

Click to expand...

No reason to be concerned if the location is accurate.

Opinions vary, but I would limit floating receptacles to locations at the corners, where when sliding the cowl on and off, the pin must enter the receptacle at an angle. The floating receptacle allows the pin to slip in easier.

I would also recommend thickening the edge of the cowl. Mine has multiple plies of glass tape there and still bows outward between fasteners when I close down the cowl exit and raise internal pressure. This might be a good place to use a few plies of carbon tape (for high stiffness) under one ply of glass tape (to isolate the carbon from the mount flange). Take a look at the outer surfaces of the cowl and the adjoining sheet metal. Shim the mount flange as needed to make them flush with each other.

Internal air pressure ranges from near zero to around 120 lbs per square foot, and in response, the cowl tries to assume a round shape. We have evenly spaced fasteners all around, except at the outlet. The result is high stress at the last fastener (or the the end of a hinge if you so choose). Save yourself some trouble later; reinforce everything in that area. I found it necessary to add a buttress at each Skybolt. Without them, the rivets were overstressed at the flange attachment.



Cowl edge thickness buildup:



It wasn't quite stiff enough:



Buttress supports for the lower Skybolts. Ignore the foam work. I was building a duct.