Gretz pitot mount

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stevewiz
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Gretz pitot mount

Post by stevewiz »

When installing the Gretz pitot mount on an RV7, what did most of you order (drilled or undrilled) I am having a hard time understanding whats drilled and what not drilled. if I order the undrilled mount, does that mean no holes in anything or is it just no holes for mounting to the spars. Thanks in advance
RV-7 N71SW reserved
Started on 10/8/2013
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bullojm1
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Post by bullojm1 »

Steve,

I am 90% sure the undrilled pitot mount does not have the holes drilled between the pitot mount and the pitot tube. That is what I bought. All of the holes to mount it to the wing/spar were already drilled.

There is also a special shallow countersunk screw used to screw the pitot to the mount. I bought 50 of these screws (min order). If you PM me your address, I will be happy to send you a handful.
Mike Bullock
http://www.rvplane.com
RV-7 | Superior IO-360 | Whirlwind 200RV
Garmin GTN650 | GRT Dual Sport SX EFIS
Status: FLYING!

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bullojm1
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Post by bullojm1 »

I found my writeup on what screws I used and how I drilled my pitot mount to the pitot tube. If anyone would like them, please let me know. Please note you will need a 6-40 tap ($3.99 at Home Depot Online: http://www.homedepot.com/p/Gyros-6-40-T ... /204625850).

Excerpt from: http://www.rvplane.com/?categoryid=7&dayid=901
One item that has been on my list for a LONG time is drilling and tapping the pitot tube for the screws that attach it to the pitot mount. The mount came with holes already in it -- I believe their diameter was about a #18 drill bit. I bought special screws for this task. Because there isn't a lot of "meat" in the pitot mount to tap, it was suggested I go with a 6-40 screws instead of the typical 6-32. The 6-40 will give me an extra one or two threads so theoretically it will be a little more secure. Another issue with this project was I couldn't drill too deep into the pitot tube because there were the wires and pressure tubes coming out of it. I could not nick either of them.

My process for installing these screws was to first mark on the pitot tube where the holes needed to be. I used a #18 drill bit for this, rotated a couple of times to make a mark on the pitot tube. Once the holes were marked. I drilled them to a #40 with a drill stop to keep me from drilling into the wires or tubes in the pitot. I then reassembled the pitot tube with the mount and countersunk the assembly for the 6-40 screw. Once that was done. I enlarged the #40 hole to a #33 and tapped the hole for a 6-40 screw. Turned out excellent.

If anyone would like some of the 6-40 screws, let me know. I needed to buy 50 of them to meet the minimum quantity order.

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Mike Bullock
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RV-7 | Superior IO-360 | Whirlwind 200RV
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Status: FLYING!

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bruceh
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Post by bruceh »

Oh no. I went with button head screws to hold the pitot tube into the mount! I'm probably sacrificing some significant speed.

:P
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TomNativeNewYorker
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Post by TomNativeNewYorker »

bullojm1 wrote:I found my writeup on what screws I used and how I drilled my pitot mount to the pitot tube. If anyone would like them, please let me know. Please note you will need a 6-40 tap ($3.99 at Home Depot Online: http://www.homedepot.com/p/Gyros-6-40-T ... /204625850).

Excerpt from: http://www.rvplane.com/?categoryid=7&dayid=901
One item that has been on my list for a LONG time is drilling and tapping the pitot tube for the screws that attach it to the pitot mount. The mount came with holes already in it -- I believe their diameter was about a #18 drill bit.
#18 would be wayyyyy to big for drilling a hole getting tapped out for a #6 screw.

https://www.carbidedepot.com/formulas-tap-standard.htm

stevewiz
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Post by stevewiz »

Thanks for the info everyone and Mike I sent a PM with my address to get a few of the screws. I will order the un-drilled mount.
RV-7 N71SW reserved
Started on 10/8/2013
Working on Fuselage as of 5/10/15 95%done
started finish kit on 7/1/16
engine on order from Barett.Will be shown at their EAA booth and then delivered to us after show

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bullojm1
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Screwed!

Post by bullojm1 »

I have shipped out screws to everyone who requested them. If anyone else wants them, let me know.
Mike Bullock
http://www.rvplane.com
RV-7 | Superior IO-360 | Whirlwind 200RV
Garmin GTN650 | GRT Dual Sport SX EFIS
Status: FLYING!

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bullojm1
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Post by bullojm1 »

TomNativeNewYorker wrote:#18 would be wayyyyy to big for drilling a hole getting tapped out for a #6 screw.

https://www.carbidedepot.com/formulas-tap-standard.htm
I totally agree - A #33 bit would be the proper pilot hole for a 6-40 tap. I think I just used a #18 drill bit to create a starting spot for the #40 drill bit. I find the large drill bits are easier to spin by hand, and they're typically sharper at the tip, making it easy to create a slight indentation in the material you want to drill. An alternative to using a punch.
Mike Bullock
http://www.rvplane.com
RV-7 | Superior IO-360 | Whirlwind 200RV
Garmin GTN650 | GRT Dual Sport SX EFIS
Status: FLYING!

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