amount of prop-blades ww1 planes

[jollyjack]

Is there a reason that most ww1 era planes have 2 prop blades only?

Maybe because of strength in case of wood, and one piece of it ... Saw an occasional 4 blade, like the new RE8, but never 3

Edited January 3, 2024 by jollyjack

[Gunfreak]

I think it's mostly down to.

1. They probably still didn't know all the in and outs of aircraft design yet.

2. Might be that the engines weren't powerful enough to get any advantage of 3 or 4 blades.

[Hans140]

2 blade prop is actually more efficient than 3, 4 etc.. The most effective are actually 1 blade props with counter-weight. There are some around on windmills and even some aircraft (silent targa motor glider). The reason for using more blades is actually limit of max. diameter with regard to engine power. There is only certain diameter you can use due to ground clearance and if you have too powerful engine more blades will transfer it better. This is also why i.e. Vought Corsair has the gull wings - to give space for larger prop.. 

[1PL-Husar-1Esk]

I think it's the horse power of the engine, it's optimal for circa 200+/- HP.

[US103_Baer]

From my reading, especially into the Hispano-Suiza development, I understand that achieving the best balance of prop efficiency/target rpm and engine power output curve, against operational requirements like climb speed, level flight speed and dive safety, was crucial to getting the most from the package.

Generally, with the engines, and fixed-pitched props of the period, that led to fairly long, slower turning 2-blade solutions.

 

However the use of gearing as seen in the later Hissos is interesting. They were able to operate/push the engine to higher rpms to maximise its power output while using a prop gear ratio to suit prop efficiency. Thus less compromise and overall higher performance.

 

Interesting example is the SE5a using Type35 Hs8B 200hp series.

The 4-bladed examples used a 2000/1170 or 2000/1333 gearing and the 2-bladed examples using more typical 2000/1500 gearing. So the engines running at 2000rpm and the prop at 1170. With the lower rpms 4 blades were found to better utilise available horspower, and the aircraft performance doesn't seem to have suffered at all. When you see an Se5a test using prop T.28096, that's a 4-blade.

Disclaimer: I'm not an aeronautical engineer, nor do i own a replica WW1 aircraft. Someone who is/does may well jump in at this point.

 

From Report No.704 into SE5a (2-blade) prop testing trials.

 

Edited January 7, 2024 by US103_Baer

[jollyjack]

Thanks, interesting; just looked at the SE5a in the game, and in RoF too; it's always a 2 blade.

Edited January 7, 2024 by jollyjack

[ST_Catchov]

Very interesting data about the Se5a and the geared Hissos @US103_Baer. Didn't McCudden experiment with 4-bladed props?

[US103_Baer]

3 hours ago, jollyjack said:

Thanks, interesting; just looked at the SE5a in the game, and in RoF too; it's always a 2 blade.

The games model (in theory, lets not go there now!) a direct-drive Viper 200hp engine, which is going to be revving up to around 2000rpm, so 2 blades. Its a derivative of the HS Type 34S

Report No.704 deals specifically with prop comparisons using this engine.

 

3 hours ago, ST_Catchov said:

Very interesting data about the Se5a and the geared Hissos @US103_Baer. Didn't McCudden experiment with 4-bladed props?

 

EDIT

So yeah 56 Sq seem to have been flying quite a few 4bladed versions when they got their first SE5as in June 1917, as opposed to earlier SE5 with 150hp engines. McCudden's 'G' was one such.

A function of using engines that required the 2000/1170 or 2000/1333 gearing. My understanding is that most were 2000/1170 actually.

Probably the 200hp Type 35 HS8Bac (1170), or possibly an HS8BDb (1333), or HS8Dd (1333). Like i mentioned, the official tests I've seen, indicate that there was little performance difference between the 2 blade and 4 blade geared 200hp engines.

Such was the shortage of Hispano Suizas for SE5as until Vipers became more available by 2nd quarter 1918 that many Hisso types were used out of necessity. There's a picture of No.84 Sq in Dec 1917 that shows them with a mixture of 2 blade and 4 blade aircraft.

 

Edited January 7, 2024 by US103_Baer

[No.23_Starling]

3 hours ago, US103_Baer said:

The games model (in theory, lets not go there now!) a direct-drive Viper 200hp engine, which is going to be revving up to around 2000rpm, so 2 blades. Its a derivative of the HS Type 34S

Report No.704 deals specifically with prop comparisons using this engine.

 

 

EDIT

So yeah 56 Sq seem to have been flying quite a few 4bladed versions when they got their first SE5as in June 1917, as opposed to earlier SE5 with 150hp engines. McCudden's 'G' was one such.

A function of using engines that required the 2000/1170 or 2000/1333 gearing. My understanding is that most were 2000/1170 actually.

Probably the 200hp Type 35 HS8Bac (1170), or possibly an HS8BDb (1333), or HS8Dd (1333). Like i mentioned, the official tests I've seen, indicate that there was little performance difference between the 2 blade and 4 blade geared 200hp engines.

Such was the shortage of Hispano Suizas for SE5as until Vipers became more available by 2nd quarter 1918 that many Hisso types were used out of necessity. There's a picture of No.84 Sq in Dec 1917 that shows them with a mixture of 2 blade and 4 blade aircraft.

 

As Baer says the first 200hp Hispano 8B versions used the four bladed prop. The 150hp early SE has a beautiful 2x scimitar bladed style (see the one below from my collection) which is slightly broader than later props.

 

The 56sq history in High in the Empty Blue says that the 4x caused more issues around adverse yaw and the 2x blade on 1918 models helped reduce that issue.

[Trooper117]

Interesting stuff guys... many thanks!

[AndyJWest]

I suspect the rarity of three-bladed props may have been partly a matter of strength. A two bladed prop can be made with a single piece of wood, with the loads balanced out, and mostly along the grain. Three-bladed props would need to be made in pieces, and joined, with the joint having a lot of tensile and bending load. Not ideal with the relatively poor wood glues they had to work with.  A four-bladed prop can be laminated from blanks with overlapping cutouts, meaning that at least some of the grain is continuous from tip to tip. 

 

 

 

 

Edited January 7, 2024 by AndyJWest