I need help identifying a WWI prop

[Rjzac67]

I have a wooden propeller that I have been told is from WWI.
There are some markings on it. I will post pics of the prop. The markings are
6 65, F.C.R., 9 -6"x 5 0 0, P.P ___ R.H., TYPE 91-H

Any help would be much appreciated!

[Dave]

The "P.P." probably refers to "Paragon Propeller" and the number that follows should be the design number.

Is the hub notched?

Pictures should help, but there are LOTS of possibilities.

[Rjzac67]

Picture of markings

Here is a picture if some of the markings on the propeller

[Rjzac67]

More markings

[Rjzac67]

A picture of the hub

[Rjzac67]

Pic of the whole prop

[Bob Gardner]

I can't identify it. I'm sure our American experts will be able to. My speciality is British and German props, not American props but there are two distinctive aspects to your prop. The diameter of 9ft 6ins with a pitch of 5ft 0ins is towards the outer limit of prop design and suggests quite a powerful engine in a comparatively slow moving aircraft; perhaps a bomber; possibly a dirigible.

The angular shape suggests a prop designed by Dashwood Lang, which hints at a prop used by the USN.

But you shouldn't pay too much attention to my view. I'm rather going out on a limb.

With kind regards,

Bob Gardner

[Dave]

Your next step is to go to this page for information about hub dimensions, then go to the linked page listing dimensions of various hubs. Many propellers with that size and shape were used on a Liberty 450 HP engine, which looks like yours would fit but you should check and be sure that they are not consistent with something else.

I am not familiar with an aircraft type of "91 H", but I'll see if I have any listings of the "P.P." drawings at home.

Is the rear of the hub notched, or is it flat like the front shown in your photo?

[Bob Gardner]

Dave,

Do you think the device on the top right of the post dated 0153am might be a USN anchor?

Bob

[Dave]

Dave,

Do you think the device on the top right of the post dated 0153am might be a USN anchor?

Bob

Yes, I do, but also you'll love this. I think it's stamped "H 16". Notice how the "1" itself looks upside down . . . Not unlike some other props we've seen, the guy hired to do the stamping got it a little wrong.

For the OP, I think yours is a variant of this prop produced by Matthews Brothers, but yours was manufactured by the American Propeller Company (Paragon).

[Bob Gardner]

Ah Yes! Well spotted, Dave. So it's a USN prop made to the design of Dashwood Lang for a Liberty-engined Cutiss H 16 flying boat. All we need to know now is if it is half of a four-bladed prop or a two-bladed prop. For forumites who have joined recently, four bladed props were difficult to store and handle on board a warship, so they were made as two bladed props with a hub that was half the size of a normal hub and two were bolted together at right angles.

This hub should be around, say, ten inches deep from top to bottom, but if it's meant to be bolted to another prop, it will be about five inches thick. (These dimensions are illustrative not factual.)

With kind regards,

Bob

[Bob Gardner]

Postscript; I should add that early examples were notched to form a square mortice joint but cracking started at these ninety degree angles and the idea of a mortice joint was discarded in favour of flat surfaces.

Bob

[Rjzac67]

Dave,

I haven't picked up the prop yet from the previous owner, so I cant check the back side of the hub until I do. I did look at the back, and don't remember seeing anything different from the front.

Thanks, RJZac

[Dave]

Ah Yes! Well spotted, Dave. So it's a USN prop made to the design of Dashwood Lang for a Liberty-engined Cutiss H 16 flying boat. All we need to know now is if it is half of a four-bladed prop or a two-bladed prop. For forumites who have joined recently, four bladed props were difficult to store and handle on board a warship, so they were made as two bladed props with a hub that was half the size of a normal hub and two were bolted together at right angles.

This hub should be around, say, ten inches deep from top to bottom, but if it's meant to be bolted to another prop, it will be about five inches thick. (These dimensions are illustrative not factual.)

With kind regards,

Bob

The published hub thickness is 7 1/4", but that will change slightly over time as the wood shrinks with drying.

Bob, I think there is a subtle difference between this presumably Paragon propeller and the Matthews Bros. prop, which uses an "L.P." drawing number and almost certainly is a Lang Propeller drawing. The Lang design has a sharp demarcation at the widest point ("diamond shaped") where the Paragon had a similar overall appearance but a more rounded appearance at its widest point at about the mid-blade position. I've seen several similar Paragon designs for several different aircraft.

[Bob Gardner]

Hi Dave,

The Lang angular shape is very distinctive and the Lang method of attaching metal sheathing is also distinctive. As Lang was the director of prop making for the USN I think he would have initially ordered props for the Navy from US and probably Canadian prop makers, made to his design. This didn't last for long. New prop designs emerged during 1918.

Bob