Prop Spinners

[jim miller]

In getting a 200 TT RV3 back flying again I have noted the large fiber-
glass spinner was never drilled for the front bulkhead plate. The rear is
drilled and has #8 nutplates. The front spinner bulkhead has been drilled
and has 4 holes with #8 nutplates but the spinner itself was never drilled.
If it has to be drilled any ideas on how? I am thinking about making
a 4 3/8 inch spacer block to simulate the prop's 4 3/8 " thickness but
small enough to drill around. Any ideas, comments welcomed.

Thanks
Jim Miller

[molson309]

I'm sure others will come up with an even better way to do this, but I would set up a tripod arrangement with a mechanical pointer that could be raised to the height of the backplate. Take the spinner off, remove sparkplugs so the engine can be rotated to any position, then rotate the prop until one of the holes is in line with the mechanical pointer on the tripod. Carefully put the spinner on, mark the spinner using the mechanical pointer, drill, and repeat until all the holes are drilled.

[Andrew M]

Drop a screw in one of the "exixsting" nut plates and another in the "bling" nut plate with the spinner off. Measure with dividers. Install the spinner and put a piece of metal tape about where the blind nutplate is. Scribe and arc. Disassemble and repeat from a different repeatable location (another known nutplate) This second location is to get a "fix" on the first arc. Assemble and repeat. Drill undersize to be sure, open up as required.
This system works well picking up a line of covered holes, with the difference being using an AD rivet to center the dividers in the blind hole, and scribing an arc out in the open on metal tape. Cover the holes with the sheet you want to drill and pick two points off the arc to put a fix on the hole. This is more accurate than hole finders.
Measurement is the enemy of precision. I tell my new guys to leave the ruler put away and get the playdough and dividers out.

[jim miller]

Since posting I bought some 6" - 3/8 all thread bolts to try this procedure.
Everything is off the plane so I placed rear backplate on my 4" extension
and then used four of the six inch bolts with the heads cut off to allow
spacing of the front plate exactly 4 3/8 inches above the rear plate using
jamb nuts and a nut on top. I then put spinner on the drilled back plate
with the front plate held in its proper position and will try to drill thru the
four nutplates on the small front plate from the inside using a #40 12"
drill bit. It is jigged up as described and I will attempt to drill when I
retrieve my long drill bit from hangar. I will let you know if it works.

Thanks
Jim Miller

[N941WR]

Get a small LED flashlight, turn it on, stick it (tape?) in the spinner, and screw the spinner in place. That should allow you to see the holes well enough to drill them.

[jim miller]

Originally Posted by jim miller

Since posting I bought some 6" - 3/8 all thread bolts to try this procedure.
Everything is off the plane so I placed rear backplate on my 4" extension
and then used four of the six inch bolts with the heads cut off to allow
spacing of the front plate exactly 4 3/8 inches above the rear plate using
jamb nuts and a nut on top. I then put spinner on the drilled back plate
with the front plate held in its proper position and will try to drill thru the
four nutplates on the small front plate from the inside using a #40 12"
drill bit. It is jigged up as described and I will attempt to drill when I
retrieve my long drill bit from hangar. I will let you know if it works.

Thanks
Jim Miller

N941
The light idea sounds good if it would work on a painted spinner. I tried the
above procedure and was able to drill backwards thru the #8 nutplates. The
#40 holes will hopefully be accurate enough to fall within the final #19 holes
needed for the #8 screws. I can't check for sure until my prop bolts arrive
next week. Thanks all for the advice.

Jim Miller

[jim miller]

Originally Posted by Andrew M

Drop a screw in one of the "exixsting" nut plates and another in the "bling" nut plate with the spinner off. Measure with dividers. Install the spinner and put a piece of metal tape about where the blind nutplate is. Scribe and arc. Disassemble and repeat from a different repeatable location (another known nutplate) This second location is to get a "fix" on the first arc. Assemble and repeat. Drill undersize to be sure, open up as required.
This system works well picking up a line of covered holes, with the difference being using an AD rivet to center the dividers in the blind hole, and scribing an arc out in the open on metal tape. Cover the holes with the sheet you want to drill and pick two points off the arc to put a fix on the hole. This is more accurate than hole finders.
Measurement is the enemy of precision. I tell my new guys to leave the ruler put away and get the playdough and dividers out.

Andrew
Excellant technique, I would have tried. Will remember for future.

JM

[frazitl]

remove the existing frontplate nutplates and drill new holes thru both the spinner and front plate at approximately 45 degrees from the existing frontplate holes. It is important that these are set up with the spinner pushed hard onto the front and back plates. Don't forget to use nylon washers under the panhead screws to ensure they stay in place and distribute the load more evenly than steel washers...