Spinner screw hole layout help

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Vision_2012

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Shady Cove, OR
I have a RV 13" spinner and base plate. How does one layout the screw holes?

I have determined the spinner circumference and divided by the number of gaps between the screws and was about to transfer this distance into a two hole drilling fixture. I am thinking of drilling the first hole (cleco diameter--1/8") and then clecoing in this fixture to drill the second. Then moving it to the new hole and drilling the next. And so on until it meets the first hole. I expect that the last gap will not be exactly equivalent to all the rest but it should be close. Then I will place the spinner over the base plate and use the spinner as a guide to drill the base plate.

I am not a machinist and only have a drill and hack saw to make this fixture with. I was thinking of a four inch length of 0.063 aluminum folded over the lip of the spinner. This seems to me a wonderful opportunity for some machinist savvy person to make this drilling fixture more robust and accurate and offer it for sale.

(btw, I am not building a metal-riveted a/c so I don't have a lot of hole lay out experience)

Or, tell us another way one can make this happen.
 

Vision_2012

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To do my own investigation, this is what I found on EAA website for builder help:

"I (By Tony Bingelis (originally published in EAA Sport Aviation, February 1987)) think the easiest way to accurately align a spinner is by doing it on the engine. First, remove the upper spark plugs so the propeller hub can be rotated easily. Then, bolt the rear bulkhead to the engine crankshaft, or propeller extension if one is used. The next step is to slip the spinner onto the rear bulkhead and temporarily clamp it along its rim with a few Cleco shoulder clamps.

Check the spinner track by rotating the crankshaft. Since it is difficult to detect a slight runout visually, turning the engine slowly by hand, rig up a dial indicator or pointer. Install the pointer at the nose end of the spinner. Readjust the Cleco clamps at the spinner rim until there is absolutely no bobble at the nose end of the spinner as the engine is turned.
When you have the spinner tracking perfectly, drill the first screw hole through the spinner and into the bulkhead beneath with a number 40 (1/8") drill bit (about 1/2" away from the prop cutout) and insert a Cleco fastener.

Recheck your alignment and then drill another hole 180 degrees opposite the first, and slip in another Cleco fastener. You can then complete drilling the remaining spinner attachment screw holes using the same procedure."


But he doesn't say how one locates "another hole 180 degrees opposite the first" or locate the holes in between these.
 

BJC

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I would cut the spinner for the propeller, then follow Tony's method. You may not end up with equal gaps between the screws that abut the propeller cutout. Do keep each screw 180 degrees from its companion screw.


BJC
 

Daleandee

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"I (By Tony Bingelis (originally published in EAA Sport Aviation, February 1987)) think the easiest way to accurately align a spinner is by doing it on the engine. First, remove the upper spark plugs so the propeller hub can be rotated easily. Then, bolt the rear bulkhead to the engine crankshaft, or propeller extension if one is used. The next step is to slip the spinner onto the rear bulkhead and temporarily clamp it along its rim with a few Cleco shoulder clamps.
This is the method I used:

ExperCraft Simple Log: Sonex # 1319

I used a craft paper trick to find the center of the spinner. Worked well for me. Spacing the screws was by measurement and a calibrated TLAR method.

If your 13" spinner came from Van's Aircraft you will find it to be very well made and easy to fit ... or at least I did.

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
125.3 hours / Status - Flying
 

bmcj

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If you have an indexed rotating table, you can place the spinner on the table and premark your lines so that they are evenly spaced, then complete on the plane as Tony Bingelis said, drilling only on the lines.
 

Vision_2012

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Shady Cove, OR
Thanks for the ideas. I will try to work with a mounted on engine back-plane.

If you have an indexed rotating table, you can place the spinner on the table and premark your lines so that they are evenly spaced, then complete on the plane as Tony Bingelis said, drilling only on the lines.
I like the "drilling only on the lines" but with only a drill press and a hack saw, this didn't include a indexed rotating table. :ermm:

From Dale's website: "There is a trick to finding the center of the 13" spinner. I used light craft paper and drew the spinner circle on the paper. Very carefully fold the paper exactly in half. I drew a line and even extended it onto the bench and marked each side of the spinner. Center the cutouts and cut slowly and note which way the spinner must go to find its was over the prop and onto the rear bulkhead."

If one folds the half into thirds and then half again, one has twelfths. Which should give me decent separation lines.
I still think a single hole drilling fixture should be used so one gets the screw installed a set distance from the edge of the back-plane.

I also want to build my front bulkhead for my warp drive prop (not wanting to buy one).
 

Daleandee

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I also want to build my front bulkhead for my warp drive prop (not wanting to buy one).
Just a word of caution about making bulkhead plates as accuracy here is extremely important. I'm using a Sensenich propeller and received a flat front bulkhead that would have needed spacers to fit the spinner correctly. Other guys that were using the flat supplied front bulkheads on their Corvair conversions were attempting to "build up" the interior of the spinner in that area to remove the space between the front bulkhead and the spinner. Result was an out of balance spinner and at least one spinner that came apart after a few hours of flight testing. I believe it is William Wynne that sells a front bulkhead that works with a Warp Drive prop using the 13" Van's spinner.

Here's what's on my Cleanex with the Corvair engine and Sensenich prop:

[video=youtube;QKo1FNZ8PCk]https://www.youtube.com/watch?v=QKo1FNZ8PCk[/video]

You also might use a protractor or angle finder on a disc to locate where the holes in the bulkhead will need to go:

tool die steel Picture - More Detailed Picture about Stainless Steel Protractor Angle Finder Arm Measuring Round Head General Tool Craftsman Rule Ruler Machinist Goniometer Tool Picture in Protractor from Very7good Technology Co., Ltd. | Aliexpress.c

Dunno if this helps ...

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
125.3 hours / Status - Flying
 
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