Dornier propeller

[chinaprop]

Hello Forum members,

I am new to this forum and happy to meet you all online. I happen to come across and bought a wooden propeller and would like to find out which plane it belonged to. It is damaged and likely replaced here on the island of Faial, city of Horta on the Açores. I know this was an important stop for the early races for records and if a plane was damaged or parts were replaced it is nice to find such provenance and get pictures from the photo archives.

It is damaged, has some cracks in it but I want to leave it exactly as is. On the back it looks that there has been paper pasted on it once and on the front there is some left which I left as well.

The length is approx 11,3 Ft (338.05 cm) The bore hole is approx 4,5 inch (10.3 cm) and it has 8 holes in the middle.

Copper lining on the front. I can email pictures of it. It says Dornier on both tips with a plane that looks like a compass rose in red and black

[Bob Gardner]

Welcome to our forum.

Your Dornier propeller is very rare. I think I have only seen one other example which is in SDTB in Berlin (the new name for DTMB). A diameter of 3380mm is large and suggests a powerful engine and that it was for a post WW1 passenger aircraft. Some of the laminations are missing. The extensive metal sheathing suggests it may have been made for a seaplane,

Dornier was founded c1923 from the ashes of the Friedrichshafen and Zeppelin companies. They made both conventional aircraft and seaplanes.

Are there any markings stamped on the hub or blades? ( I think probably not on the hub because of the missing laminations.)

With kind regards,

Bob

[Bob Gardner]

Postscript; the fact that you found it in the Azores suggests it might well be from a Dornier flying boat, even from the famous Do X flying boat. (For other forumites the Azores were a stopping point for much of the air traffic across the Atlantic between the wars. )

Bob

[chinaprop]

Thank you Bob for your response. Yes it must have been a seaplane maybe we can find out which one as there were not that many landing in Horta. There are no markings other than the Dornier logo´s on it. It looks like missing lamination but as they are exactly the same on both sides of the hub I think there was an aluminium assembly to hold it. What intrigues me is that there is paper glued to it as you see on the tip. The back is the same. Could it have been a spare they kept here? for these seaplanes?

[chinaprop]

Considering the paper stuck to it it might have been a spare part as if I am correct Lufthansa wanted to open a route through the Azores across the Atlantic. I have to search wich plane they intended to use. It would make sense to have spares along this proposed route.

[Bob Gardner]

Looking at your photographs again, it has dawned on me what I should have seen earlier. Your prop may not be missing two laminations. It is particularly thin because it is half of a four bladed propeller. Large four bladed propellers were obviously bulky and difficult to ship anywhere. Two halves occupied much less space. This is exciting because the Dornier Do X had four bladed propellers. But I know very little about Dornier flying boats. It might be that all of them used four bladed propellers comprising 2 x 2 bladed prop. But if not, it is possible that your propeller is from a Do X. Let us know what you discover on Google etc!

With kind regards,

Bob

[Dbahnson]

Bob, I think there was another reason for 4 bladed props being stacked 2 bladed props. It allowed tolerance for expansion and contraction of the wood without creating defects in the wood or the glue joints themselves. Any of the very old 4 bladed props I've owned have shown weakening of the joinery at the hub over time. I think with the stacked blades that process is accommodated by the stacking arrangement, so that the grain in each blade remains lengthwise.

You can see it on the edge of this FE8 prop, but it's extensive throughout the hub.



Actually, here's a better view of the same prop.

[chinaprop]

Hello Bob,

That would be really exciting and it makes sense to have some sort of connection on these locations be it aluminium or wood. I send an email to the museum in Berlin, they might know more. As far as DO x arrivals here I can check the library archive in Horta, might find more there than on Google. There must be a list of Do X planes arriving in Horta.

I also thought it could be a push propeller but could not find any info on that.

Th only length I could find for the DO x prop is 355 cm but as different engines might have been used with different optimum rpm speed the prop might have come in different lengths.

[Dbahnson]

I also thought it could be a push propeller but could not find any info on that.

Many (but not all) pusher propellers were left hand thread. Yours is right hand.

[chinaprop]

drawing from popular mechanics 1929

Hello Bob,

This drawing illustrates exactly your story above and size wise it is more likely. The strange thing is that only one Do x ever landed here on the way back from New York after the botched record attempt to cross the Atlantic.

[Dbahnson]

Notice how those props are "stacked" but not "notched". I think what Bob was alluding to was that your prop looks as if the hubs are machined to fit together without doubling the thickness of the hub. Lots of US built props were constructed that way.

Also, notice in the picture that those are left hand props. Yours is right hand.

[chinaprop]

Thanks for your feedback, so I need to search for another type. I send an email to the Dornier museum. If anyone is supposed to know they should but no reply yet...it is interesting where this search will lead me.

[Bob Gardner]

Dave,

The Dornier Do X, which weighed I believe 56 tons, had twelve engines, six each of tractor and pusher props, mounted in six pods above the wing. So tractor and pusher propellers were used.

With kind regards,

Bob

[Bob Gardner]

Dave said;
Notice how those props are "stacked" but not "notched". I think what Bob was alluding to was that your prop looks as if the hubs are machined to fit together without doubling the thickness of the hub. Lots of US built props were constructed that way.

Dave, I didn't mean that. I think this hub is flat and mated to a similar flat surface on the other hub.

With kind regards,

Bob

[chinaprop]

Message from the Dornier museum

Hello,

I got an email back from the Dornier museum in Germany. As we can not find markings in the hub area but considering the length it is quite certain this prop is from the Do-x. This would make it very rare indeed. We try to find a place that has another one to compare but that is not easy. The saga continues because if it is from the Do-x maybe there is a mention in the logbook about one of the props being swapped on Faial. They had plenty of props on it that could get damaged considering the long journey they made on their transatlantic journey. Sure they carried spares