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Spinner Gap Question

PCHunt

Well Known Member
Sponsor
I just finished modifying my old spinner to fit over my new-to-me (used) Catto Prop. There is a gap between the spinner and the prop, see photos. I have a couple of questions:
Will this much gap be unsafe to fly in any way?
If not unsafe, how much efficiency will I lose?
(The gap looks larger in these photos than it does in "real life")

Gap1-1.jpg


Gap2.jpg


Gap3.jpg


Gap4.jpg


Gap5.jpg


Thanks, as always!
 
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Fly on, Pete!

My buddy doesn't even have that plate on his -4. His gap is over an inch on the back side.

Ellipse, (the prop guy) says to have as close as possible fit for efficiency's sake, less drag but I figure that you can make a new, tighter fitting piece later on.

Regards,
 
Pete,
The only problems you will have with this kind of a gap is cosmetic and a little extra drag. The airplane will fly just fine.
But, hey, it's fiberglass. Put on your boat builder's cap and fix it.
 
Pete, hang loose a few days. I'm fitting a new spinner and expect to start on some glass cover plates with built-in joggles tonight. I can probably post a photo how-to, assuming you're ok with a little glass work. I think you can close your gaps with new cover plates.
 
Ok Pete, let's get you going. Pull your spinner and clean up the edges of the cutout; straight (where desired) and sanded smooth.

First we make a quick mold shell. Tape off the outside of the spinner from one opening to the other:

Taped.JPG


Paint on some PVA mold release, let it dry, and lay up three plies of 9 oz glass, extra wet and no bubbles because we want the inside to be slick:

Mold%20Layup.JPG


When cured, pop it off and trim the loose edges:

Mold%20Removed.JPG


Cut it in half, then tape a section firmly over each blade cutout:

Mold%20Trimmed%20and%20Taped.JPG


Flip it over and apply two coats of PVA to everything in the area. Let it dry between coats.

PVA%20Coats.JPG


To be continued. No, yours won't have the flanges.
 
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The mold shells mean the new gap plates will match the curvature of the spinner, precisely match the shape of the opening, and will have integral flanges.

Get out the cutting board and prepare 8 identical pieces of 9 oz fabric. These were 5 x 6, but you may need a different size depending on your cutout. Stack four each on two sections of plastic sheet. Cut a plastic cover sheet too. Mix about 50 grams of epoxy. Pour a little of it in another cup and set it aside. Pour the rest on the two fabric stacks:

Saturating%20Fabric.JPG


Ignore the small stacks in the above picture; more flange material for my installation.

While the resin is soaking the stacks, grab the other cup you previously set aside and mix in some micro, plus just a pinch of flox. Make it about like peanut butter. Wipe in a small fillet around the edge of the prop cutout:

Micro%20Filet.JPG


Fabric can't fill this joggle; if you try you'll wind up with a trapped air bubble. The fillet material allows the fabric to smoothly lay over the joggle without trapped air, and it will precisely define the cutout edge on the finished part.

Go back to the fabric patches, add resin to any dry spots, and lay a plastic sheet on top of the pile. Roll or squeegee to fully saturate the fabric and remove excess resin, plus any trapped air:

Roller.JPG


Cut right through the plastic to trim the saturated fabric stack to the desired final size. Carefully peel the plastic off one side, and place the stack:

Trimming.JPG


Layup%20Placed.JPG


In my case I had to trim around the flanges, but you won't. Smooth it down, starting from the center and working outward to remove any trapped air bubbles. Now carefully peel the plastic sheet off the top. Use a cheap chip brush to stipple down any disturbed fabric and remove any remaining air.

Add a flange to the wet fill plate by clamping something slick to the existing spinner flanges, wiping in a small flox filet, and adding layups for the necessary flange thickness.

Flange%20Addition.JPG


More tomorrow.
 
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BTW, if you're wondering about the glass flanges on the inside of the above spinner, here's the rest of the deal:

Spinner%20Backplate%20Milling.jpg

Spinner%20Backplate.jpg

Backplate%20Finished.JPG

P3170006.JPG


The spinner screws go in from the back when the cowl is removed. No exposed screws; a "screwless" spinner. I've seen it elsewhere done a few different ways, so....
 
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About 8 hours since layup. The new part is "green", not fully cured but hard enough to pretty much do as you please. The green stage is handy; you can abuse the part to get it out of a mold (within reason, because it is not brittle), you can easily trim with scissors, etc. Still not cured enough to sand very well.

Pull all the tape off the shell mold and remove the shell:

Mold%20Shell%20Removed.jpg


Flip it over and slide a sharp flat tool up under the flanges:

Flange%20Separation.jpg


Pete, your plate will probably fall right out at this point, but if not just give it a sharp rap on the outside with a small ball peen. Mine needed the rap because of the additional backplate flange.

Here's the rough trimmed filler plate with flanges. Since it was molded in the spinner cutout, it will perfectly match whatever cutout shape you might have, and that should fix your problem. From here it's just trim to fit around the prop blade, add nutplates if desired, and surface finishing.

Plate%20Rough%20Trimmed.jpg


Blade%20fairing.jpg


Good luck!
 
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Fantastic tutorial!

Dan- that's a fantastic tutorial! I have not done any fiberglass work, but I have a buddy at the airport that is a pro. Your postings have given me the knowledge to have a go at it, and I'm sure my buddy will help.

Greatly appreciated!:)
 
Pete

Looking at the photo's, personally I'd de-rivet the piece off the spinner back plate and make a new one. The rest looks quite close.

Peter
 
Yup

I agree with you for the back ("face") side, but the gap on the front is as much as 3/4". That's where Dan's tutorial will be put into use.:cool:
 
Oh yeah, you will definitely un-rivet your old cover plates and toss them.

After you lay up new ones and start trimming to match your prop, your edge will be roughly like the black line, the red line being what you have now:

 
Outstanding Tutorial

Gees, Dan, that is spectacular work. I am just getting ready to cut my spinner. Couldn't be better timing. This definitely looks like the way to make the gap seals. Thank you.

Michael Wynn
RV 8 FWF
San Ramon, CA
 
Finished up mine this weekend:

Spinner%20Finished.jpg


Note how a constant speed prop must have a gap around the cover plate regardless.

The cover plates have a brushed shell of ClearCoat on them right now, so the edges are thick. They'll get sanded flush later when I fill and finish the spinner. I elected to open some edge gap too. There will be some finishing buildup, and I want to be able to get the spinner shell on and off without chipping.

In retrospect, for the filet wipe substitute a firm mix of epoxy and cabosil rather than epoxy, micro, and a pinch of flox. The micro is a little soft for an edge.

A word to readers on this "screwless spinner" thing. There are a few flying (I don't know how many), but I consider it experimental. The internal glass flange attaching the spinner shell to the backplate has to be done right or you could have a spinner separation. 'Nuff said.
 
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Attach pictures

Hi Dan,

Reviving this thread.

Could you please repost your instructions for the screwless spinner with attached pictures, now that we have that option?

Finn

(Found this thread while looking to see why Van's specify 14! screws in the back plate -- have 10 in my RV-3B 12" alum spinner, had 12 in my old RV-3 12" FG spinner. Do not like installing nut plates!)
 
Hi Dan,

Reviving this thread.

Could you please repost your instructions for the screwless spinner with attached pictures, now that we have that option?

Finn

(Found this thread while looking to see why Van's specify 14! screws in the back plate -- have 10 in my RV-3B 12" alum spinner, had 12 in my old RV-3 12" FG spinner. Do not like installing nut plates!)

A 13" spinner has a larger circumference than a 12" spinner.
The extra two screws keep the spacing from getting any larger than what was used on your 12" spinner.
 
A 13" spinner has a larger circumference than a 12" spinner.
The extra two screws keep the spacing from getting any larger than what was used on your 12" spinner.

Thanks Scott.

Yes, figured that might be the case. So FG spinner needs more screws than alum, probably because it's more flexible, which also makes me wonder about not having screws in the front plate with FG spinners. I guess with enough rubbery (compressible) material (RTV?) between font plate and spinner it will take up the slack when the spinner expands due to centrifugal (?) forces.

Interesting, DWG "SPINNER" calls for adding material to inside of spinner, not to the front plate flange, unlike what most posts in this thread calls for.

20 screws are a lot with a wood prop where you have to check torque fairly frequently.

Finn
 
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