Skybolt Opaque Cowl Install

[mfleming]

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]

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]

Originally Posted by Mikeyb

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]

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]

Originally Posted by mfleming

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]

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]

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]

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]

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]

Originally Posted by aitor11

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