hercules props

The place to raise issues, ask questions, swap ideas and discuss anything related to aircraft engineering, maintenance and building.
NB Any opinions expressed in this forum are not necessarily those of LAA Engineering

Moderators: John Dean, Moderator

Post Reply
phil brookman
Posts: 73
Joined: Tue Aug 12, 2008 4:40 pm

hercules props

Post by phil brookman » Fri Jan 08, 2016 11:38 am

i heard of someone replacing his evra prop for a hercules on a jodel with good effect ..does anyone have any info on this ,,
016580

User avatar
Alan Kilbride
Posts: 300
Joined: Sun Jan 13, 2008 4:41 pm
Location: York

Re: hercules props

Post by Alan Kilbride » Sun Jan 10, 2016 12:12 pm

Yes me. See 120 performance thread.
As an aside another 117 has just fitted a Hercules, but has yet to test fly it. If you are prepared to wait, we will put together figures for both aircraft as a comparison.

Alan
037174

User avatar
Alan Kilbride
Posts: 300
Joined: Sun Jan 13, 2008 4:41 pm
Location: York

Re: hercules props

Post by Alan Kilbride » Sat Jan 23, 2016 8:14 am

Test flight on 2nd Jodel fitted with a C90 and a Hercules 68" X 56" propeller today. Will post results later.
037174

User avatar
Alan Kilbride
Posts: 300
Joined: Sun Jan 13, 2008 4:41 pm
Location: York

Re: hercules props

Post by Alan Kilbride » Sat Jan 23, 2016 5:06 pm

Figures for the 2nd D117 with a Hercules 68" × 56" are.

2000rpm.......87kts
2100rpm.......100kts
2250rpm.......105kts
2350rpm.......112kts
2475rpm.......120kts.

Alan.
037174

G.Dawes
Posts: 279
Joined: Wed Jan 02, 2008 11:00 am

Re: hercules props

Post by G.Dawes » Sun Jan 31, 2016 8:44 pm

What are the level flight attainments of this prop as it seems to be fantastic to obtain so much speed at those rpm, I could not get anything like that on mine 90 knots is about all I could get in level flight at 2450rpm, I feel I must have a drag parachute deployed to lose out so much performance with just a prop change. I get figure like that in a dive but nothing like it when level. Are these planes super light, streamlined with good spats and gap closed joints? An EVRA d28/1 has a length of pitch of 69"X 52.5" . anything more than that will prop bind the engine and allow the rpm to be held way down on the power scale for takeoff and climb. a jodel with a D28/9 will not climb at all well and that is a pitch of 55.5"
I also have a McCaully metal prop to go on mine and that does go a bit faster and more economical, but the takeoff run and climb is nothing like the same. I wonder what performance Brian gets with his D117 set up.???
Graham Dawes
028225

User avatar
Alan Kilbride
Posts: 300
Joined: Sun Jan 13, 2008 4:41 pm
Location: York

Re: hercules props

Post by Alan Kilbride » Sun Jan 31, 2016 11:21 pm

There is always one. The Earth is not flat. The fìgures are there. Not in a dive. 2 Jodel D117s with identical props show very similar figures. I have no wish to enter a pi$$ing contest, as I said on the D120 thread, when a query was made and my name was mentioned.
I frankly couldn't care less anymore. Have you tried flying your 117/120 properly?. 2450 and only 90 kts wasn't what my 117 was producing with the D28 1B. At 2450 rpm and 100kts was a more likely figure.
I am now going to pull the video I put online to prove my figures. I no longer intend to discuss this affair.

Alan
G-BJOT
037174

Brian Hope
Posts: 1271
Joined: Tue Jan 08, 2008 8:28 pm
Location: Sheerness Kent

Re: hercules props

Post by Brian Hope » Mon Feb 01, 2016 7:56 am

Hi Alan, there will always be doubters so try not to get too uptight about it. I certainly have no reason to doubt your figures, I might be a bit more sceptical if you were claiming you were getting the extra performance for free, but by your own admission you are not, your fuel consumption has increased. My belief is that the engine is pulling more manifold pressure and thus producing more power and can therefor handle a coarser prop. There is a limit to how far you can push this before the engine won't play ball and performance falls off, and if you go too far engine damage can occur. Rupert seems to have found the sweet spot with his prop, and with two examples now producing very good performance I can't see any reason to doubt the validity of the figures.
Graham isn't comparing eggs with eggs anyway, because he has modified his canopy and turtledeck; it is taller and wider and I would consider that it is therefore creating a deal more drag than a standard airframe (his is also a converted 112 rather than a stock 120 or 117, not that that in itself should make a difference).
Cruise on my 117, which has an Evra cruise prop, is 95kt at 2350 for a fuel burn of 21 litres an hour on either avgas or mogas, there is no discernible difference.
014011

Post Reply