Jump to content

A conundrum...


nigel_d.
 Share

Recommended Posts

Fully clothed for this cold weather I weigh 86 kilos, I have a 31 Nucleon and a V5. just lately I have been doing some fuel consumption tests for different speeds. It turns out that to fly with trimmers fully out I used 2.9 litres an hour and fully in 2.4. Also trimmed fast I'm doing 25.5 mph and about 21 trimmers in.

Bit slow in comparison to heavier loaded wings.

I'm in the bottom of my wings weight range, if I had a smaller wing to achieve greater speed does it follow that I would increase fuel consumption? It seems obvious to me that it would unless someone here could explain otherwise - perhaps a smaller wing would have less drag so as to balance it out maybe?

My tests involve putting a measured amount in an empty tank and then after a timed flight empty the tank and measure the remains in a calibrated jug.

I have heard various claims that seem too good to be true given the pilots weight and speed etc. - I wonder if such claims are based on the not-so-accurate tank tube/gauge as their basis.

Thanks in advance

Nige

Link to comment
Share on other sites

I think the best way is to weigh the fuel not measure it. Have an empty tank weigh it and add fuel. The when you have done say 2 hours at slow trim come in and weigh the tank again..... 711g = 1 Ltr

i am not sure going on to a smaller wing will give you less fuel economy If your at the bottom of the weight range of the Nucleon 31, Stepping down too say a 29 is not too big a jump. Plus like you said smaller wing less drag.

Make sure you have the correct all up flying weight with everything you need to fly. Allot of people under estimate there total all up weight.

Can you use speed bar, Do you loose hight on full trims+bar or do you gain? This with let you gauge weather or not the wing is correct for your power/weight.

On my old V3 1.1, 50kg's thrust i was getting 3.0 LPH on full trim +bar, slower trims i would get around the 2.5LPH

Fusion 26,

Pilot 75kg

All up around 120kg's

I have not yet done any figures on my V5 due to crappy weather.

Link to comment
Share on other sites

I remember from my machinery lectures many years ago, the tutor saying when he tested machinery for fuel consumption, they would weigh the fuel rather than use a volume measurement. Even quite small temperature variations during the day would throw the readings off, specially with a volatile fuel like petrol.

Link to comment
Share on other sites

It does climb on full speed bar and trim but I didnt keep it on long enough to see how fast it climbed as it hasnt been run-in enough yet. So far I have just over 4 hours on the V5, I wonder how others are getting on.

The temperatures before, during and after my efficiency test flight didnt vary more than a few degrees so I imagine the weighing fuel method would have probably returned similar results but certainly something to consider for future tests.

Cheers

Nige

Link to comment
Share on other sites

If your motor is just running in then IMO there is not point doing econ test's in till you have properly bedded the it in..... When you have around 10 15 hours then do your test's again.... Weighing the fuel is a much more accurate way than measuring it... Thats why they do this in the comp's and you have to weigh the fuel if you are doing any FAI record attempts.

I have posted on here before about kev @ our fuel he said he was getting around 2.5 LPH on a synth, Pilot around 100kg.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



×
×
  • Create New...