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Drilling tailcone longerons

unitink72

Well Known Member
Page 10-11, Step 2. "Match drill all the common holes of the F-1073 Side Skins into the F-1032 Longerons using a 3/32" drill"

Do they really want me to use a 3/32 drill for these? usually the plans say use a #40 bit.
 
Yes, it makes it a little tighter fit. Prior to this step I thought a 3/32 was synominius with a #40. VAF corrected me... word to the wise make sure when you make those HS brackets that you drill in the right place. I notched them and had to replace my longerons... wasn't fun.
 
Ok, glad I asked and didn't just assume #40.

Appreciate the tip. My longeron bends look mighty nice and would rather not scrap them!
 
Oops. I used a #40. Once the skins are dimpled and the longerons countersunk I doubt that there will be a significant difference but I did email Van's for their opinion.
 
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Step #3 then says to final drill all holes in skins to frame with #40. I THINK they want you to use 3/32" bit on initial drill just to make de-burring easier, but not really sure why you can't just drill #40 to start and deal with larger burrs. In order to dimple or counter-sink, holes will need to be drilled at #40 just for the counter sink bit or dimple die to fit in. That pilot knob on the CS bit and dimple die will force the hole open to #40 even if you don't drill them out to #40.

If I recall, I followed the plans (3/32" match drill step 2, #40 final drill step 3) but felt it was redundant.
 
Step #3 then says to final drill all holes in skins to frame with #40. I THINK they want you to use 3/32" bit on initial drill just to make de-burring easier, but not really sure why you can't just drill #40 to start and deal with larger burrs. In order to dimple or counter-sink, holes will need to be drilled at #40 just for the counter sink bit or dimple die to fit in. That pilot knob on the CS bit and dimple die will force the hole open to #40 even if you don't drill them out to #40.

If I recall, I followed the plans (3/32" match drill step 2, #40 final drill step 3) but felt it was redundant.

I'll have to go back and have a look at step 3 now. Sheesh. I think I know what I'm doing and get into autopilot mode. My autopilot needs an assumption and enthusiasm damper. :D

What you said about the CS bit and dimple die are absolutely correct which is what left me scratching my head yesterday. FWIW I emailed Van's and Sterling said "no big deal". Carry on.
 
RTFM

In order to dimple or counter-sink, holes will need to be drilled at #40 just for the counter sink bit or dimple die to fit in.

Good point I hadn't thought it out that far. This has basically turned into yet another question that begs the usual response, "Read the instructions, stupid!"

FWIW I emailed Van's and Sterling said "no big deal". Carry on.

Cool thanks for the update.
 
I think the reason for the 3/32" first with just the side skin in place, is so that once the top skins are put in place and attached you final drill them with a #40.
 
****. I also read 3/32" Drill and translated it to #40 bit as well. Glad to see I'm in good company.

Also good to hear that the official word is "build on" since the holes needed to be #40 to dimple. (Which I should be starting in the next day or so)

*Edit: Laughing that a word that sounds like a structure that holds water is being edited out :p
 
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Since you're using a hand held drill on a relatively (compared to the skin) thick piece, you'll get a slightly better hole with the 3/32" -#40 procedure than just going #40 from the start. Some carry this one step further and use a reamer for the final finish.
 
Since you're using a hand held drill on a relatively (compared to the skin) thick piece, you'll get a slightly better hole with the 3/32" -#40 procedure than just going #40 from the start. Some carry this one step further and use a reamer for the final finish.

This would have been my preferred method if I had realized as I actually like the results from my reamers.
 
I think the reason for the 3/32" first with just the side skin in place, is so that once the top skins are put in place and attached you final drill them with a #40.

I used a #40 reamer for the final pass with the top skin in place.

One tip that Van's gave that was infinitely valuable to ensure straight holes was to use the reflection of the drill in the aluminium. That was an awesome suggestion.
 
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