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-   -   Skybolt Opaque Cowl Install (https://vansairforce.net/community/showthread.php?t=203195)

mfleming 01-25-2022 05:00 PM

Skybolt Opaque Cowl Install
 
Installing the Skybolt fasteners with a gelcoat cowl and Skybolt pre made flanges has me perplexed.

I get using the magnets or triangulating the center hole...thats working.

What I don't get is upsizing the hole with a step drill. Skybolt tech support says each time a new step is drilled recalculate which direction to go to find center.

Also: I only have 10 cleco inserts, Do I get as many holes drilled as possible to final size and then install the skybolt fastener to hold everything in place to do the rest?

What Im missing is: What to reference to decide if you centered or not? Once you are using the step drill, the cleco centering insert is not there and the existing hole is bigger than the 15/32" hole you're drilling, so it's no help.

Just to save everyone time:
  • My flanges are already riveted to the firewall (I'd like to not make my own)
  • Even with the gelcoat sanded off, the cowling is too opaque to accurately use a light.
  • I can't get to the back side of most of the flanges.
  • I only have two floating receptacles and anyway they only give you a very little bit of leeway.

Mikeyb 01-25-2022 05:41 PM

I agonized over that part as well. I used the magnet inserts. I found the hole location I determined with the magnet was inaccurate, particularly near the steel parts of the motor mount. I found it necessary to drill the holes oversize then put a cleco in the hole and trace the outline of each cleco body on the cowling and use the step drill to “walk” the hole to match the cleco circle then push it up to final size.
I bought extra magnet inserts
Mike

mfleming 01-25-2022 05:55 PM

Quote:

Originally Posted by Mikeyb (Post 1584707)
I agonized over that part as well. I used the magnet inserts. I found the hole location I determined with the magnet was inaccurate, particularly near the steel parts of the motor mount. I found it necessary to drill the holes oversize then put a cleco in the hole and trace the outline of each cleco body on the cowling and use the step drill to “walk” the hole to match the cleco circle then push it up to final size.
I bought extra magnet inserts
Mike

Once you had the cleco body traced on the cowl and you then used the step drill to get to final size....did you go on faith that the hole was now centered or was there someway to check as you were headed to final size?

Mikeyb 01-25-2022 06:23 PM

I did a few at a time first and found that the outside of a sharpie line around the cleco ended up almost 7/16” in diameter and if I made sure the step drill was concentric with the line until it disappeared under the drill I could carefully drill up to 15/32”. Fortunately it worked. I have all fixed receptacles in all the fasteners.

agent4573 01-25-2022 06:26 PM

Quote:

Originally Posted by mfleming (Post 1584698)
Installing the Skybolt fasteners with a gelcoat cowl and Skybolt pre made flanges has me perplexed.

I get using the magnets or triangulating the center hole...thats working.
That's good, this is probably the hardest part.

What I don't get is upsizing the hole with a step drill. Skybolt tech support says each time a new step is drilled recalculate which direction to go to find center.
The instructions are vauge, but it summarizes what you do. You basically just look through the little hole and see which way it has to go. After that, each additional step in was side loaded to correct a little bit of direction. By the time you get 2-3 steps away from full size, it should be very minor corrections. The sam james cowl was semi-transparent though so a bright light would highlight the flange edges. After you drill to 1/2" or 9/16" you should be able to start to see the flange by looking through the hole or using a small mirror. There's still plenty of meat to correct back to center from this point. For a few of them, I also drilled the #40 hole centered, then used that center point and a compass to draw a 15/16 circle on the outside of the cowl. You can then use this circle as a reference if the stepper bit starts to walk. You'll still want to try to look through the hole on the last few steps to line it up with the flange. I missed far enough on 1 that I needed to use the full floating back plate instead of the normal one, but I didn't have to redrill any holes.

Also: I only have 10 cleco inserts, Do I get as many holes drilled as possible to final size and then install the skybolt fastener to hold everything in place to do the rest?
Or leave the cleco insert in every 4th or 5th hole. This will let you drill all but these few to full size. Then install the fasteners and return for the final 5 or so cleco'd holes.

What Im missing is: What to reference to decide if you centered or not? Once you are using the step drill, the cleco centering insert is not there and the existing hole is bigger than the 15/32" hole you're drilling, so it's no help.

You could also try a cheap boroscope camera if you really want to see the hole. Drill up a size, stick the boroscope in and take a picture. Adjust accordingly and drill up the next size.

9GT 01-26-2022 07:49 AM

1 Attachment(s)
I've got Skybolt's that I may or may not use on my cowling. My idea is if I do, I will fabricate a final size drill guide out of 1" x 3" x 1/8" steel, heat/oil harden it, then locate it and attach to the cowling with two way carpet tape and a couple spring clamps. Sneak up on the final hole size and finish it with a final size reamer. After I have that hole done, warm the steel up a little with a heat gun and with a putty knife remove it. Clean off used tape and adhesive, repeat. For curved surfaces, trace out the hole with an ultra fine tip pen, get close to the line with drill and carbide burr in a Dremel, then finish with a reamer if needed.
I used to use a pair of loop glasses I borrowed from a friend who is a dentist for close up work.
I found these magnifier glasses from HF at $4.99 to be far easier to use and worked just as good. I use these quite often for close up work, especially wiring.

rongawer 01-26-2022 09:56 AM

Use an end mill
 
If you put some packing tape on the cowl over the work area, then wipe the steel pin and tape surface with some light oil (I use tool oil), it will allow the dowl pin to find the magnet center more accurately. Works good.

And then, instead of a step drill (unibit) to recenter the hole reference, try a cheap end mill from Amazon. Put it in a variable speed drill and use it to work the hole centered over the skybolt magnet. I have a drawer of these end mills, so I generally start with a 1/8" to find the center, and then finish with a 1/2" end mill.

They give more control for cutting direction and are very good at quick and precise cuts. Just don't use your expensive carbide bits as the fiberglass will quickly dull whichever cutting edge you use.

BTW, I got 19 sets of magnet Hole Finders in my Skybolt FWF kit for the RV-10

wirejock 01-26-2022 10:11 AM

Skybolts
 
Lots if tricks. My method worked except for one or two. I filled those with flox and redrilled with the light.
Tape the cleko grommets to the flanges. Install the top cowl. Use any existing fasteners to lock the cowl into position. Use the Howe jig if you have it. Drill the accurately measured spots #50. Tiny hole. You want to hit the cleko hole. Enlarge to #40. Hit the cleko hole and gently walk the hole to center. Should be pretty close. Enlarge to #31 hitting the dead center of the cleko hole. Cleko and repeat with the other 7. Remove the cowl. Cleko the grommets to the holes. Trace the diameter of the hole inside and out. Enlarge but watch carefully so the hole remains concentric.
The only difference between the floating and the others is the flange is slightly smaller. You can grind th flanges to match a floater and make as many as you want.

aitor11 01-26-2022 12:23 PM

1 Attachment(s)
I just finished doing this. I did get all correctly drilled, but your mileage may vary.

Let me try to explain my method:

- Install the receptacles.
- Put the cleco holder in place (you can tape it or just have someone hold it for you).
- Insert something that is roughly the same size as the cleco hole and use that as a guide to draw lines (I used a awl).
- Draw six lines into the fuselage. Two of them will be parallel between themselves every time. I made the groups roughly 0, -45 and +45 degrees between themselves all moving aft from the awl.
- Did all receptacles this way.
- Installed the cowling.
- Using the six lines for each hole I draw them into the cowling until they all intercepted.
- Made a #30 hole at the intersecting point for each receptacle.
- Enlarged them with the step drill.
- Done.

Weefle 01-26-2022 02:16 PM

Quote:

Originally Posted by aitor11 (Post 1584906)
I just finished doing this. I did get all correctly drilled, but your mileage may vary.

Let me try to explain my method:

- Install the receptacles.
- Put the cleco holder in place (you can tape it or just have someone hold it for you).
- Insert something that is roughly the same size as the cleco hole and use that as a guide to draw lines (I used a awl).
- Draw six lines into the fuselage. Two of them will be parallel between themselves every time. I made the groups roughly 0, -45 and +45 degrees between themselves all moving aft from the awl.
- Did all receptacles this way.
- Installed the cowling.
- Using the six lines for each hole I draw them into the cowling until they all intercepted.
- Made a #30 hole at the intersecting point for each receptacle.
- Enlarged them with the step drill.
- Done.

Thanks for posting this. I think out of all the methods described before you this one I can grasp.

Keith

mfleming 01-27-2022 10:29 PM

How I centered my Skybolts on an opaque cowl
 
Thanks for all the great replies.
So I started installing the Skybolts on the upper cowling.
I'll document the technique for the upper cowl that I finally settled on for the historical record ;)
  1. With the flanges riveted in place, tape a skybolt cleco insert in the flange.
  2. Triangulate the center of the cleco hole with a 6" rule and sharpie. I used a center line and two obtuse angles.
  3. Install the upper cowl and tape in place. Make sure it's what you want.
  4. Extend the triangulation lines from the fuselage to the fiberglass cowl.
  5. Drill a #30 hole where the three lines meet. If the hole is not perfectly centered, use the drill bit to elongate the hole so its centered on the cleco hole.
  6. Cleco the cowl in place and trace a circle around the cleco body. (not really necessary as you guide the hole through observing the receptacle)
  7. Rivet the Skybolt receptacle to the center top flange (I had to remove and then reinstall the receptacle locking device to rivet the holder due to possibly damage from the squeezer.
  8. Enlarge the center top hole in the fiberglass cowl with a step drill a couple of steps (not much) with the cowl off.
  9. Install the top cowling and cleco...make sure it fits the way you want.
  10. Observe the enlarged hole and draw arrows in the direction it needs to move to be centered on the receptacle.
  11. Remove the cowling and use the step drill to guide the hole in the direction indicated by a couple of steps.
  12. Repeat until the hole is final sized and centered on the receptacle.
  13. Install a Skybolt recessed washer and locking lug.
  14. Install the cowl and set the locking lug depth by screwing it in until flush.
  15. Repeat the the process until all Skybolts are installed.

I installed the center skybolt and then did the one on either side at the same time and then the next two on either side after that. The more skybolts that were installed, the more confident I was to do more than one at a time.

Lots of on and off this way but its working well.

RV7Guy 01-28-2022 12:24 PM

Inserts??
 
Did you get the little inserts that go in the flanges? The have a hole in them for silver cleco. Makes alignment a breeze.

mfleming 01-28-2022 02:08 PM

Quote:

Originally Posted by RV7Guy (Post 1585437)
Did you get the little inserts that go in the flanges? The have a hole in them for silver cleco. Makes alignment a breeze.

Yes, I have the little cleco inserts but with an opaque cowling, I wouldn't call it a breeze :cool:

Edit: Congratulations on your Grand Champion RV-7 Darwin!!

AlphaCharlieBravo 02-02-2022 07:48 PM

Skybolt Recievers
 
I received the complete FF Skybolt Kit for my RV-7. It included the SK245A162A receivers as part of the kit. They are brass colored, accept 2 1/8th rivets. It looks as though there is no room for the shop head to expand.

I cant find one picture on anyones site of one of these installed to see what the rivet will look like set. Can anyone of you please either post a picture and if not able to send me a PM and Ill include my email.

Thanks very much.
Arnie

wirejock 02-02-2022 09:42 PM

Rivets
 
Quote:

Originally Posted by AlphaCharlieBravo (Post 1586619)
I received the complete FF Skybolt Kit for my RV-7. It included the SK245A162A receivers as part of the kit. They are brass colored, accept 2 1/8th rivets. It looks as though there is no room for the shop head to expand.

I cant find one picture on anyones site of one of these installed to see what the rivet will look like set. Can anyone of you please either post a picture and if not able to send me a PM and Ill include my email.

Thanks very much.
Arnie

They set right up against the edges of the receivers. If using a squeezer, the thickness of the shop head will stop at the thickness of the receiver metal. If you have any floaters, compare the two. Only differencenis the dimension of the exterior of the receiver. Easy to grind to match if you need a little float.

DanH 02-03-2022 07:56 AM

2 Attachment(s)
Won't help Mike, but if you have not yet installed anything, note the root of the problem...drilling through the cowl so as to match the existing holes in pre-made Skybolt flanges.

The simple answer is don't use premade flanges. Make your own, without the big center hole. Trim and fixate the cowl, drill though into a blank flange.

Use straight flanges along the sides, no scallops. The scallops tend to catch the corners of the cowl when installing the cowl after service...and chip the paint. Didn't think of it at the time, and really wish I had.

8's and A models should get a little filler strip at the lower corners, see below.

Just like the hinges in a standard install, the Skybolt flanges across the flat bottom of the cowl are under a lot to stress due to the unsupported length across the cowl exit. I run high internal cowl pressure, making the problem worse, and I started seeing signs of rivet stress where the flanges are riveted to the firewall. So, the four sockets down there got "flying buttress" braces, like an upside down "Y", riveted to the firewall and the two ears of the Skybolt socket. Bad photo below.
-

AlphaCharlieBravo 02-04-2022 08:09 PM

Thank you Larry for responding so quickly. I now see the difference between the floater and the fixed style. I received floaters in my kit as well.

Also because of an earlier post of yours I ordered extra cleco adaptors.
Looking forward to getting these flanges mounted, engine hung and start working on my James Cowl.

Thanks again.


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