Carving Props

For many years, I attended the National Model Competitons hosted by the AMA, both in Vincennes and Muncie. One of my favorite events was the Pylon racing, both for the speed, quality of the models and the high performance engines. Many of the participants carved their own props -- a good prop seemed to include good aerodynamics, a steady hand and a dash of VooDoo thrown in. They would sit on the flight line with pitch gauges and scrapers tweaking away and favorite props were cherished.

Robert, you have my admiration -- anyone who can carve a functional prop has some serious skills.

a--

Thanks Andrew, That is very kind….. I would loved to have walked those QM rows… I used to see them in the magazines and marvel over them…. I love to continue to learn so the props will keep me busy for awhile…..You can even take the turn with knives, scrapers, sharpening, etc….. A lot of little trails to follow with model airplanes…. Electronics is one you are very well versed in….

Robert

Epic pictures Robert. Epic. The static shot is beautiful.

Hot is Texas. Yes, news is all over it. Hot in Canada too. West Virginia right in the middle geo wise currently experiencing cooler than normal temps.

Hi rdw77,
Nice carving ! Like the 'curved back' tips.
Last wood prop I worked on is an old TopFlight maple? 6-3. Sanded and cut down to 5-3.
Very careful not to change the pitch, removing whatever coating was on it.
It was quite 'flexible'.
I used CA to seal, finish the bare wood. Last coats get wiped on. Easy to balance. Stiffer.
Untried, but last time I tried, the exhaust of a Cox engine goes behind the prop.
Your results will vary,
Take care,
Have fun,
Dave

Thanks Bob, Dave

I looked into CA as a finish Dave but ran into some data that mentioned nitromethane was hard on it…. Methanol OK but cautioned on nitro…. This was on a data sheet of one of the CA makers, Can’t remember which one though….On the surface seems like a good idea… It would certainly strengthen a wood prop and I know instrument makers sometimes use it as a final finish …. If you run your rehabed prop more let me know how it holds up…. It’s tempting to try CA…

Got the 6-2 finished…. Somewhat modeled after a Top Flite white nylon but left a little thicker near the hub…. I think I’ll give it to my son …… I gave him my “Pretty Bee” that’s in my avatar and it’s displayed on his office desk….

Hi rdw77,
Beautiful props!
If I had raw nitro methane, I could probably melt epoxy joints. Same with CA.
I have taken apart very fuel soaked (tank leak) noses and repaired them.
Problem is, the wood soaked in raw fuel, and got replaced.
Weather you use dope/lacquer/varnish/epoxy/CA or others, you seal the wood, so fuel does not get in.
That is it.
Over the decades, I have found CA easier/ better/cheaper than epoxy.
Try CA. (I use the Dollar store stuff)
Your results may vary...
I wonder the .049 RPMs on a wood 6-2...
Take care,
Have fun,
Dave

Hey Robert Nice looking prop man you nailed it ! As far as finish I just read a little on it in two places here is on one finishing ( Most wooden props are finished clear with marine spar varnish, and there’s an option to have the back of the prop painted black to reduce glare. Sensenich has tried other finishes on props, Rowell says, but as with the resorcinol glue, old school still works best so they’ve stuck with spar varnish. On boat brightwork, the spar varnish often gets renewed every year, but on props, it lasts for years. That’s probably because most wooden props are—or should be—hangared, and thus don’t see much UV light, which breaks down the varnish surface film.   Taking from here > https://www.kitplanes.com/wooden-props/  

Eric, the link you gave led me to another article:
https://www.kitplanes.com/the-case-of-the-missing-propeller/

I didn't know that the threads on prop bolts are rolled, not cut, which are stronger.

Kit Plane about the prop bolts:

The prop separation required mandatory engine overhaul, $15K US.

This is my Tornado Plastikote 7x2 prop:


You oft hear of the 6x2. This size prop was a rare find for me, picked it up several years ago for my Cox .074 Queen Bee. It would probably work good on a .049 Bee.

Thanks for that bit of info Eric …. Spar varnish sounds like a good option….. I used it on my wooden engine test stand and my .020 glider and it’s holding up well…. I chose dope in the beginning for the props thinking it could add a bit of strength to the wood…. Truth is I’ll probably break them before I have to worry about a long life finish LOL!!!…. I may just try the spar varnish in the future ..,, The finish on these makes them easy to balance…. I sort of watch balance thru the whole process of making….Toward the end of applying finish coats, Just add a little more to the light blade for final balance …

That 7-2 is certainly unique George….. Probably would be good for a Texaco type…. Slower rpm, Lower gear ratio…. Good gas mileage….Pulls a larger bird into thermal country …. Thanks for sharing that

rdw777 wrote:That 7-2 is certainly unique George….. Probably would be good for a Texaco type…. Slower rpm, Lower gear ratio…. Good gas mileage….Pulls a larger bird into thermal country …. Thanks for sharing that

Actually, I wouldn't be afraid to put that on a Golden Bee or Black Widow. Those, the 6x3 prop (depending on manufacturer) is the optimal prop to put it within its power band in air. Compared with the Tee Dee (speed engines), the reed valves are torque engines, able to turn larger props (within reason) with ease.

Going one size up and one pitch down IMO would have close to the same RPM, may be a slight touch down. But for a draggy airplane, would put the wind easily past the fuselage. For a draggy airplane, would give more bite in the air, help it to move along with better velocity (same logic as the 5x3 replaced by a 6x2 on Babe Bees).

Hi rdw777,
I found the wood pusher prop I carved ~1972 ! (looking for something else as usual... )
That poor O.S. Pet .15R/C... never had a chance !
Limited cooling air, metal film canister muffler, pushing, And, over propped no less...
Kept running, and easy to start till the end. Lost power. Now, I know why !
The prop is:
-a very wide blade 8.5/~3.
-cedar, with iffy grain direction. ~1/8th grain thickness !
-still seems stiff, but it will not run on an engine again.
-the shape, finish is still good ! ~1/2hr running time.
-guarantee it was sealed with buterate dope. (no other options then)
-it got 'sprayed' with castor oil each running time. Still 'shiny'.
Hope this helps,
Take care,
Have fun,
Dave

That’s nice you still have it Dave…. If it flew then you were successful…. Welcome to post a photo here …. Thanks for sharing that

More prop carving madness….. I was making guitars about fifteen years ago and still have  a variety of hardwoods that I used for them…. This one is from Cocobolo….. A good bit harder than Mahogany but can still be carved with a knife…..3.75 x 3 ….In its rough carved state…. Still needs final shaping and clean up….



I made a tool to square up the faces …. Ken mentioned this tool in my prop balancer thread…. Spin the props in an empty crankcase to check fore and aft tracking… I think was mentioned by aspeed, … Thanks guys….



I must be getting old because I’m really enjoying whittlin’ on little pieces of wood LOL!!

Hi rdw777,
I am only allowed on the internet to improve my english/typing skills. (50% in HS due to perfect attendance!)
I was quite 'vocal' about about allowing TI function calculators in tests. (Sliderules were OK )
The 0/1 concept of this computor still bothers me.
I have a 1990s era digital camera that I need to learn to connect here. Just need more time to learn !
Anyways...
Nice prop! The grain of the cocobolo looks great...
After the failure of the nylon 8-6 pusher prop to taxi the PushyCat, an old geezer gave me an old (Air Trails?) mag that had an article on carving props. I followed the directions. It flew.
Thinking about low pitch props...
Has anyone tried a 1pitch prop?
(nice 7-2 gg!)
Take care,
Have fun,
Dave

Double Post

Watching how they laminate props on the real thing makes me think one could use hardwood plies to make one, have a custom ply layered power prop.

I think this one will be difficult to balance




This was amongst my late brother's stuff when we cleaned out his storage container.  I believe it was a result of a nose-over in his Luton Minor following a gear collapse caused by a heavy landing.

As I dug further into the container I discovered this.






Obviously a replacement for the broken one, but for some reason it appears to have never been flown, although it has clearly been mounted.  It wasn't the one fitted to his plane when his wife sold it, so the reason it wasn't used we will never know.  It's a (Barry) Bishton prop.  As you'll see in the picture, suits VW1600 and is 1.5D X 0.72P.  I assume that's Metres.  My theory is that he wasn't happy with how it felt.  The mounting face of the crankshaft wasn't cleaned before it was mounted and I reckon is was imbalanced due to the undercoat.
As you will see, it's made from three thickness layers, but the hub also shows that the rear lamination is also laminated width-wise.
Rod.

I’ve seen instructions for laminated props on plans for rubber powered planes George…. So I’m sure it could be done for a power prop as well….May add some strength and stability too….

That’s interesting they would make the rear lamination in three pieces Rod…. I’m sure it was done for reason, Probably strength…. Regardless, Looks like a very tricky joint to get those curves to mate at an angle like that….

This one is about ready for finish…. I think I’ll try spar varnish….Coco is a very oily wood that needs to be cleaned with a solvent before it can be glued….. Will have to do the same to apply finish….



Cocobolo scrapes well so I dug out my old card scraper to help with shaping….It rolls up nice little shavings like a micro plane when tuned up well….

Hi rdw77,
Beautiful prop. Like the aerodynamics...
Nice carving. A nice edge on a scraper is under rated...
I am a retired wooden boat builder.
Here is the history of 'spar varnish'...as I know it...
Lighter woods got used for masts/booms on sailboats. They came up with a 'spar varnish' to protect them.
Later on, WW1 happened and 'spar varnish' was still good. And was used on the early props of the day.
Some how to this day.
Spar Varnish, is to detect flaws in the soft mast/boom/spars and to repair under way.
Greasy/oily woods like Teak, just need oiling.
Try wet sanding with castor oil,
And buffing it.
Take care,
Have fun,
Dave

That’s cool Dave….Wooden boat building would require some very special techniques, bending, joinery… etc…. You’ll have to share some of what you did…. What kind of boats?

I got to know spar varnish in my career for being good for UV resistance…. We had an old theater with some big ornate exterior wooden doors….The painters were having a hard time keeping them coated so I asked them to switch to spar varnish….. We could get a couple of years from a treatment before having to re-do….

Baking the varnish in the Texas sun to harden it up…. Good idea Eric

Is anybody familiar with "Howard Feed-N-Wax" Home Depot/On-line.

I have used it on gunstocks for years. It will clean and re-new the worst conditioned vintage stock saving the original wood. Each year I wipe down my firearms with it including the hardware. It will also restore faded plastic model airplanes. Miracle stuff, used it on the Infant prop and many others.

Hi rdw777,
Built a Mirror Dingy last year of high school. In the basement. After learning sailboats could go upwind.
Many types over the decades.. Favourite is a DN Iceboat, I gave up, due to hand problems and no more ice.
Wet water sailboats seem too slow now, but still get out, bumming rides at the docks...
I could go on...
Spar Varnish is great to use. Block wet sanded to mirror finish. Last coat, perfection...
It is just too soft. Unless you like varnishing.
2 years in Texan sun? Most of the boats here needed spring/fall almost constant maintaining.
More later, if you want,
rsv1cox,
Real beeswax is good. Predates other finishes,
Try boiled linseed oil, better. (not raw linseed oil!)
Tung oil, best but expensive...
Your results may vary...
Take care,
Have fun,
Dave

Hi Bob, Not familiar with the product but looks interesting… Orange oil and beeswax….Great for wood but I can also see how would be good for dried plastic….. Beeswax can buff to a nice, soft shine…. I sorta have similar ingredients…. I use lemon oil on my guitar and keep some beeswax around to lubricate saw blades…. Works great if the wood is trying to pinch the blade during the cut…




Thanks for sharing those Dave…. I had a friend many years ago that taught me in a small sailboat…. Single sail and a well for your feet…. Kind of exciting when the wind tilts the boat on edge…. Can make surprisingly good time ….Gotta be OK with getting dumped occasionally…. Not so much for me these days….