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Bob Grimstead
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Posted Thursday, March 1, 2012 @ 09:25 PM  

Hi Guys,

I am not in the habit of advertising, even when a friend is producing a good product, but I and others have discovered that Rupert Wasey of Hercules Propellrs has been making wooden airscrews that confer a measurable performance increase to our aeroplanes.

I've written an article, which I hope you will all soon be able to read, but here's the numerical detail missing from the story (cut and pasted from another less appropriate thread):

The new Hercules prop increased WGN's sea-level climb rate from 620fpm to 770fpm, in identical conditions less than one hour later, which I make a 24 per cent improvement in climb rate. Both those numbers were taken in the first minute of climb from 300 feet amsl.

Climbing at full throttle for five minutes, the numbers were 580 to 712 fpm , which is a 22 per cent improvement. I believe that the lower figure for the longer climb was because the end altitude was significantly higher, and so the engine was becoming much richer and therefore producing less power at the higher altitude.

I specifically asked Rupert to maximise climb rate rather than improving speed, but his new propeller also increased top speed by one knot/mph and cruise speeds by two knots/mph.

They cost around 750 GBP (pounds Sterling) but they confer a significant performance improvement (for us, anyway).

You can see me making the full-throttle Vne dive test and then flying some exuberant aerobatics (including 180-degree half upward vertical rolls and stall turns to the left) here:

http://www.youtube.com/watch?v=IvP_l-A73Lg

Visit: www.hercprops.com for more info, but don't be impatient. Like the guy who built a better mousetrap, Rupert is currently swamped with orders!

Yours, Bob

[Edit by Bob Grimstead on Wednesday, March 7, 2012 @ 02:17 AM]

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Bob Grimstead
Captain

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Posted Thursday, March 1, 2012 @ 09:32 PM  

Immediately after flying the test with the un-painted Hercules propeller.

The finished article, with custom-made Hercules glassfibre spinner.

Rupert now makes spinners in the same shape as the original Fournier spinner, but held in place more securely to resist cracking. They can be uses with or without the starter ring back-plate.

Yours, Bob

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Bob Grimstead
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Posted Wednesday, March 7, 2012 @ 10:03 AM  

Hi again Guys and Gals,

I have e-mailed a pdf file of my Pilot magazine Hercules article to Collin and Steve, in the hopes that Collin can put it on the CFIAmerica web site and he or Steve can provide a link to it here. Meanwhile here are a few facts to ponder.

There are many, many more variable parameters to propellers than just their pitch and diameter, and they are all important, although they won't appear in the manufacturer's designation, or even proabaly in his published specification.
A prop blade can be compared to an airplane's wing. Diameter and pitch are directly analogous to wingspan and incidence.
There are two sorts of RF4D in aviation. Both have the same 11.3 metres wingspan, and identical 4 degrees of incidence, but you would not expect our Fournier RF4D to perform the same as the McDonnel Douglas RF4D Phantom!

So you cannot expect a Newton, Lodge, Hoffmann, Evra, Culver, Tennesee, Heliptera or Props Inc propeller to perform like a Hercules propeller of the same diameter and pitch, or even like one another. Diameter and pitch only tell a tiny part of the story about your (any) prop.
As well as the number of blades, their diameter and pitch, other important factors include: blade chord and thickness, aspect ratio, twist, taper, pitch distribution or helix angle, the aerofoil or combination of aerofoils, camber, planform and tip shapes.
In the same way that a wing's aerofoil, aspect ratio and thickness/chord ratio are vital to its performance, these things are also the most important for a propeller, although since most of the prop's work is done at the outboard few inches, tip shape is also very important.
Just for interest, I measured the chord and thickness of two excellent props I happen to have in stock, measuring these parameters in inch units at one-inch increments inboard from the tips (neither of these is a Hercules prop).

Station prop E chord prop E thickness prop T chord prop T thickness
1 inch 2.678 .415 2.168 .315
2 inches 2.868 .430 2.377 .351
3 inches 3.073 .465 2.619 .384
4 inches 3.859 .492 2.845 .420
5 inches 3.461 .517 3.091 .448
6 inches 3.622 .537 3.303 .469
7 inches 3.797 .591 3.499 .503
8 inches 3.961 .627 3.570 .540
9 inches 4.101 .656 3.881 .593
10 inches 4.220 .683 3.949 .633
11 inches 4.346 .718 4.026 .690
12 inches 4.460 .772 4.139 .743

It is interesting that prop E is not only much wider and thicker and less tapered, but that its areofoil is clearly very forward loaded, with its point of maximum thickness apparently at around 25% to 30% of the chord. It could well be an ancient Clark Y aerofoil, much beloved of propeller makers over the years merely because they know and trust it and it has a flat underside, which makes the props comparatively easy to carve. But since Virginius Clark devised it empirically way back in 1922, NINETY YEARS AGO! maybe it's time for something a bit more modern and efficient?

The slimmer prop T has its maximum thickness much further aft, at perhaps 40% chord. Aft-loaded aerofoils generally work better at high Mach numbers, and guess what speed your prop tips are going at full throttle?

Neither of these props is a Hercules prop, and when I get back to Britain I'll measure that one for comparison, but this is just to warn you that diameter and pitch are such a small part of a propeller's effciency, that they are almost irrelevant on their own.

Yours, Bob.

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SteveBeaver
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Posted Wednesday, March 7, 2012 @ 11:03 PM    YIM

Here ya go:

http://sbeaver.com/Fournier/March_Hercules_final.pdf

Bob Grimstead
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Posted Wednesday, March 7, 2012 @ 11:10 PM  

Thanks very much Steve & Collin.

Yours, Bob

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Bob Grimstead
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Posted Saturday, July 7, 2012 @ 07:03 AM  

Rupert Wasey at Hercules Propellers now has in stock a brand-new propeller optimised for a 1400cc RF4D.

It works extremely well, and Matthew can supply performance details.

The only reason we aren't using it ourselves is that we want identical, slightly coarser than optimum props for our display work (for quiteness and rev limitation in the full-throttle Vne dive case -- something nobody else has to worry about).

I thinks the standard price is around £750, and it's LAA-approved. Bolt on and go!

For those British Fournier owners on a BGA Certificate of Airworthiness, don't despair.
There will obvioulsy be an approval process, and it's unlikely to be more difficult than the LAA's, particularly since this prop is already approved by the LAA.
Rupert has all the strength calculations ready, lamination glue samples etc, and all we have to do is bolt it on, fly a test flight with a few simple readings, and then fly it for five hours to prove it isn't made of chocolate.

Have a go.

Yours, Bob

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Bob Grimstead
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Posted Thursday, August 16, 2012 @ 06:07 AM  

Hi again Guys,

Rupert says the standard price for this propeller would be £690, but he is prepared to take offers.

It will be painted in the colours of your choice.

Buy now, while it's on his shelf and ready to go.

Yours, Bob

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Bob Grimstead
Captain

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Posted Monday, April 8, 2013 @ 09:55 PM  

Sorry Guys, but that one has been sold.

Better check your wheel is properly locked down before landing.

Yours, Bob

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Markku
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Posted Tuesday, April 9, 2013 @ 01:55 PM  

It's waiting to be bolted on the OH-380 nose

[Edit by Markku on Friday, April 12, 2013 @ 08:57 AM]

Bob Grimstead
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Posted Thursday, April 21, 2016 @ 04:49 PM  

I've realised that I didn't record all the numbers for my Hercules propeller, so...

16th October 2011, G-AWGN, 1776cc JMR engine, Hercules 52/37 prop (actual pitch 36.88 inches).

Conditions: 17°C, 1024 HPa, calm. Altimeter set to 1013 HPa.

Climbing at 70mph (3,000rpm) from 100ft after one minute 870ft, so 770fpm.
After five minutes 3,660ft = average 730fpm

Wide open throttle at 1,500 feet = 122mph at 3,300rpm

Max cruise at 3,100rpm = 111mph

Economy cruise at 2,800rpm = 99mph all at 1,500 ft on 1013

I really must get this propeller signed off by the LAA (and the bigger engine too, I guess)

Yours, Bob

[Edit by Bob Grimstead on Thursday, April 21, 2016 @ 04:56 PM]

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Fredrik S
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Posted Friday, April 22, 2016 @ 04:32 AM  

I will post an update on XSK after i've flown it with the new prop.
It looks like a beaut though and everybody at the club that has seen it so far thinks the prop looks really great (and different) .
We have a little different diameter/pitch on ours so it will be interesting to compare with Bobs numbers.
Our Hercules prop is 53/42 inches. close to our old one but a bit bigger diameter and a bit higher pitch

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Best regards
/Fredrik Svanberg
RF4D serial#4104 SE-XSK

Bob Grimstead
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Posted Saturday, December 17, 2016 @ 03:13 AM  

Hi Folks,

I have been so impressed with the improved performance of Hercules propellers on several airplane types (Fournier RF4D, Pietenpol Air Camper, Bowers Fly Baby and Staaken Flitzer among others) that I got one for our Champ.

One very simple test flight revealed an 11.6% performance increase in climb rate of 703 feet per minute rather than 630fpm.

Cruising at 2,300 rpm I got 101mph with the Hercules prop rather than 98 mph with the previous propeller just 45 minutes earlier.

Because it also revs at a couple of hundred rpm less than the former propeller for a given throttle position, I will happily bet that the Hercules prop will give me a significant improvement in fuel economy too.

Just for your general information

http://www.hercprops.com

Yours, Bob

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