Disc Loading....what is too low?

[Chopper Reid]

No need apologizing Tony, I knew what you were talking about. Just thought I would throw my answer in for those who might have less experience.

And BTW, I'm one who has a few hours up on my gyro but have little knowledge of flying other makes so I'm very familiar with the Rosco but I know that other gyros are going to be a whole new ball game.
The recommended disc loadings are probably the area to start with.

[MilesW]

Tony,

Disc Loading is derived by dividing the AUW of the Gyro by the Disc Area...this will give the upper limit.
Then do it again empty of fuel. There's your ultimate lower limit.

Pie (3.1416) X Radius Squared (Feet) = Disc Area (sq/ft)

AUW (lbs) / Disc Area = Disc Loading (lbs/sq/ft)

21 fT Blades

21 divided by 2 = 10.5 radius ft

Therefore, radius squared is 10.5 X 10.5 = 110.25 sq ft

3.1416 X 110.25 = 346.36 sq ft

500 lb AUW Gyro Divided By 346.36 = 1.44 lbs sq ft

Cheers,

Mitch

This is a bit like looking at a "penny dreadful's" books. Something just aint quite right. At the very least, wouldn't the disc area be the total swept area less the non effective area of the hub bar?  Because of the nature of circles, you are going to end up with quite a different number. On face value, the disc loading value as calculated above is pretty much meaningless. Someone using the above could be led into beleiving something that ain't right. There must be more math! A fairly complex formula with quite a few more variables I'm guessing.




Miles

[greg mitchell]

Miles,


There must be more math! A fairly complex formula with quite a few more variables I'm guessing.



Like I have stated above several times, eliminating the need to "guessing" there is an excel program which is far more detailed and includes many more variables.
This is what the gyro community have been using for a long time now, if it is so dreadfull, then OK, so show us the real math.


The above formula for calculating disc loading is the basic std formula.

Birdy,

We can start with 60 footers then and work back from there!

Mitch.

[greg mitchell]

"usually connotes rather careless and second-rate writing and gory themes."

I've had a few private emails today asking what a Penny Dreadfull is.......

Careless and second rate.  Well!

LOL!

Sorry Miles.

I think it's time for me to bow out!

I'm off to make changes to The Monarch, new Landing Gear and Blades. (Yes Tony, I spoke to Gerry G, awaiting more info, still undecided.)

Thanks to the few who contributed to this thread.

[MilesW]

"usually connotes rather careless and second-rate writing and gory themes."

I've had a few private emails today asking what a Penny Dreadfull is.......

Careless and second rate.  Well!

LOL!

Sorry Miles.

I think it's time for me to bow out!

d.

Sorry Greg,

It was neither careless nor second rate, and definitely no gore. I didn't even know of this connotation!!

The reference was in the context of the penny dreadful stock. Typically exploration plays where the prospectus and ensuing press releases use "interesting" calculations for future earnings and the really creative stuff like probable, proven and inferred reserves. You want to believe it, but you just know there is something missing. Maybe not so well known outside of WA where the penny dreadful has been turned into an artform!

Bit late in the day now, but when my brain is next in functioning mode I'll post a bit of math to ponder.




Cheers



Miles

[Mark Horan]

Actually, when people come into a topic fresh, they can quite often make observations that those of us with "Knowledge"  overlook.

Personally, I have always thought that the disc loading calc is a bit agricultural when looking at pounds per sq ft loading. If 28 ft blades had two blades of 14 ft the calc may have some relevance, but the same sized disc with 10 ft blades and an 8 ft hub bar (for the purposes of discussion), logically wouldnt have the same loading per sq ft as the original disc.

waiting for someone to tell me how wrong I am?

Mark.

[birdy]

Very rong Hoorang, how can you measure a 'disc' in 'square' feet.

[greg mitchell]

Actually, when people come into a topic fresh, they can quite often make observations that those of us with "Knowledge"  overlook.

A 28 foot hub bar will give you the same disc loading as the example you gave but a very different blade loading, which is where the chord will obviously have some effect.

I let you continue with the thread now you are involved Horan, I have modifications to make, upgrades to install and a new set of blades to purchase.


Mitch

[Mark Horan]

Actually mitch,

What it will give you is the same loading on the teeter bolt.....if you can get enough power to get the machine off the ground.

Good luck with your modifications


HORAN

[greg mitchell]

Obviously Horan it is riduclus to think with all the other parameters that the thing would fly....however, it is still an imaginary disc, whether spinning blades or lumps of wood, with a calculable loading......not a teeterbolt loading formula. We can agree to disagree I guess.

I must concentrate on other matters now as I believe this thread has run its course for me.

Thankyou for your offer of good luck with my mods.

Mitch

[greg mitchell]

Seeing as I kicked this thread off I should advise on where it has led me to and the decisions made for blade and loading selections.

Just confirmed a set of 25' Gerry Goodwin Blades. Fabricated bonded alloy with 1 1/4 lb tip weights. 7 3/8" Chord.

Total weight 25 footers approx 59 lbs give or take the inaccuracy of the bathroom scales.

I believe a set of Dragon wings is around 53-55 lbs.

The Goodwin Blades can be hand spun.

The tip weighted blades were recently tested by a well known experienced pilot who ordered a set immeadiately.

At my AUW at sea level the new GG blades will spin up around 363 rrpm with a disc loading of 1.42 psf

MT the blades will be spinning around rrpm 348 and disc loading of 1.30 psf

At half fuel 356 rrpm and disc loading of 1.36 psf

With a full load of fuel at 2,500 feet rotor rpm will be up near 380 rrpm, which is where I am at now at sea level on take off fully loaded with a dic loading up around 1.52 psf

Further by adding the Goodwin blades I save 17 lbs off the weight of the Patroneys and increase my disc size from 23 1/2 ' to 25 '  this helps to offset the additional weight of the GFLG for an over all net weight increase of just 8lbs.

Thanks to those fellas who talked me  through a lot of this stuff on the phone over the last few months.

Thanks to Tony Denton and Echo for putting me onto the Gerry Goodwin Blades.

I have found the Beatty Excel rotor performance work sheet to be spot on with indicated rotor rpms given a mean lift coefficient value of .5 whilst flying the Patroney Blades.

Thankyou

Mitch

[Graeme Monro]

Now you blokes have done it, I think you broke my brain.

[tonydenton]

mitch, thats great news. i'm not saying stay with them for ever but they are great fun. you'll notice the difference with the lighter rotors, easier spin up. i will be drooling over your landing gear. please us up to date.

[greg mitchell]

"As stated before, I have flown over 1,400 sets of blades, all the way down to .9 lbs. per ft.
I can say WITHOUT reservation, that anything below 1.3 is BAD! It will cause the little B's to be like a leaf in the wind! IF, and I say If, you were to ONLY fly in dead calm wind then it MAY be safe to use 1.0 lb.per ft.. But, back in the real world, we know low time pilots, especially, will not know when to NOT fly, until it is too late! the ONLY way I can help prevent this from becoming a BAD thing , is to offer my experience and NOT sell blades to a person , knowing it is WRONG!"

Ex USA Forum......

Gives a definitive statement with a 'number'.

Sure he's only one bloke, with one point of view.....BUT he's been building gyros for many, many, years (Dominators) and has flown various craft and blades through out those years, with different blade loadings.
Based on Ernie Boyettes experience and knowledge, I'd be inclined to at least listen to this advice.

Mitch

PS. Tony I'll give you a ring when I have the Goodwin Blades up and flying.

[birdy]

Your safe Mitch, Jerry rang yesterday.