View Full Version : Mahogany propeller for Curtiss OX JN3

11-08-2017, 08:18 AM
I have an "early propeller"; it's 8'3", mahogany, and is for a Curtiss OX JN3. I figure it's from about 1915.

American Propeller Company, Baltimore, Maryland, Paragon
Curtiss OX JN3
Right Hand 8-3x5.00

It also is stamped 686 above the CURTISS OX JN3. What does the 686 mean?

And it is also stamped (next to the center hub) C.A.B. and below that the number 6. What does that mean?

Thank you.

11-08-2017, 08:10 PM
The "686" is likely a serial number and the "C.A.B." is likely an inspector's stamp. Pictures of those would help.

11-11-2017, 10:05 AM
Thank you.
Attached are photos showing the markings.
I'd appreciate your feedback.

11-11-2017, 02:20 PM
Can you post a photo of the entire propeller? The best way to take it is to center the camera so that it's "looking" straight down the center bore hole.

The decal looks to be in beautiful shape, which is always a big plus. I'm curious about the metal hub. I've not seen one held in place with screws like that (nor have I seen screw holes in the wood itself) and I don't see a keyed slot to lock it onto the crankshaft, although that may just be the way the photo is taken.

It might be worthwhile to remove the metal hub assembly to see what is underneath it.

No revision to my comments about the stampings, and the CAB certainly is typical of an inspector's stamp.

11-11-2017, 03:53 PM
Attached are photos of the entire propeller and a closeup of some damage on one end. I believe this is water damage. But the rest of the propeller is in excellent condition.

I am reluctant to remove the metal hub.

The hub area on the back side looks identical to the hub area on the front; I do not see any "keyed slot".

Notice that the center is a light colored wood, maybe maple, while the rest is laminated mahogany.

I wondered about 686 being a serial number, because from my research, it sounds like there were only around 100 JN-3s manufactured, so unless the manufacturer started numbering at 600, it doesn't really make sense.

11-11-2017, 09:45 PM
The stamped number is really a "serial" number and is not specific to an aircraft production line, so while it might have been one of a series for the JN3 it was probably the 686th propeller they had stamped with a serial number. It's an early number, since there were over 25,000 Paragon props manufactured by the end of WW1, which makes sense since the JN3 was an early version of the more common JN4, "Jenny".

The geometry is very similar to this JN4 prop (http://www.woodenpropeller.com/Jenny.html) of mine, and may have utilized the same blueprint. It's strange that the decals seem to be on the rear of the blade rather than the front. (The "front" of the prop was usually slightly curved, while the "rear" was typically flat, and the leading edge tends to be rounded vs. the trailing edge which is thin and more fragile.) Also, I can't figure out how it was attached to the crankshaft without a keyed slot to keep it from spinning on the crankshaft under power.

I suspect that the color is just variation in the color of the mahogany. Usually when alternate species of wood were used they were alternated throughout all of the laminations, or else the odd species was just on the front or rear surface.

All that aside, it's a propeller that is worth keeping and is likely to appreciate considerably in value over time. It's remotely possible that it has been "restored" at some point, although based on the photos alone it doesn't look as if it has been.

11-12-2017, 04:18 PM
Thank you so much for this useful information.

I had assumed - incorrectly - that propeller serial numbers would correspond to airplane numbers.

I've been trying to decide what to do with this propeller. Now I think I'll hold onto it and hang it on the wall - that's what my children think, too.

11-12-2017, 08:31 PM
I've been trying to decide what to do with this propeller. Now I think I'll hold onto it and hang it on the wall - that's what my children think, too.

Good move. I try to give that advice to a lot of people.

I honestly believe that rare propellers (and I'd put yours in that category) are currently undervalued, while more common propellers are overvalued. Some of the offerings on eBay are ridiculous, for instance. So if you can bring yourself around to the concept that it's both an investment vehicle as well as a nice decorative piece to admire and enjoy for the present, the decision should take care of itself. :D