Luga Propellers

55 posts in this topic

Posted

I just got an email back from Luga, he has been away at a competition of some sort and he is in and out of contact right now.  Be patient, he will get back to you for sure,.

 

:BC:

 

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Posted

I just got an email back from Luga, he has been away at a competition of some sort and he is in and out of contact right now.  Be patient, he will get back to you for sure,.

 

:BC:

 

Yep, I got the same email.  Said he got my money and all is well.

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Posted

I got a reply as well (same excuse for the delay). Did you notice that there is a new name again? We need to add another slash... Kool/Luga / NRProp

http://nrprop.com/index.html 

I have not found any real explanation to the differences to expect between the "S" series Scimitar and the "C" series Classic form blades. The Scimitar makes less noise  I believe, but what about performance? It looks nice...

Minor difference in price :
580 euros for 3 SL106/1750 blades
535 euros for 3 CL104/1750 blades
hub (20 euro - appears very cheap)
all including shipping  

 

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Posted

Hey Fred,

the info I have about the c blades vs sc blade shape is that the c blades are able to absorb more Hp as they have  much more cord and blade surface. Look at the difference on the picture.

 

20171215_172820.jpg

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Posted

Hey Fred,

the info I have about the c blades vs sc blade shape is that the c blades are able to absorb more Hp as they have  much more cord and blade surface. Look at the difference on the picture.

Thanks - sounds right... I assume it means that I would need a longer Scimitar blade to get the same thrust...
In the proposal I received both blade types are the same length. The quoted blades are shorter than what indicated that I could take (did he quote by memory while still travelling or did he study my case before replying..?).
With my limited understanding of this very complex topic is that for STOL planes the longer the prop the better... I currently have a short 3 blade warp drive and friends with the longer warp drive also get better cruise speed... 

(I got 92 HP at full throttle on my Simonini Victor 2)  

Current gut feel is that the I should go with the longest possible Scimitar blades... does that sound right?
 

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Posted

Hey again,

 

this propeller choice topic I believe is very complex. I am by no means an expert but I will share what / the way I understand this. Please do chime in if I am on the wrong path looking through thick mug........

You have to throw in one more important variable......reduction ratio of your engine (if you have one)!!, the higher the reduction ratio (2.47 vs 2.27 for example), the slower your prop turns which allows you to run a bigger diameter propeller (prop tip speed stays subsonic). A bigger diameter propeller is more efficient and provides more thrust. This obviously has it's limits as you will need the Hp & torque to do that ( for example if you take a rotax 912 80Hp with a 2.27 reduction, there is no point fitting much higher reduction gear and a big Dia. prop as the power would be lacking... 

Now if you take my engine as an example....I have a rotax 912 fitted with the Xtra kit (95Hp) and the original 2.27 ratio reduction. This obliges me to use a smaller prop at higher pitch setting to get the most out of it. Ideally though it would be better to have a 2.47 reduction fitted and use a larger diameter prop at lower pitch setting for best efficiency.

The Item I am a pretty lost is this damn 2 bladed vs 3 bladed issue (why do I see most using 3 blades???)... Now Imagine the same blades, same manufacturer with one setup in 2 blade and another setup in 3 blades....which is better???????  I do not like to compare different propellers/blades makers as you will add another variable there.

 

If someone is out there and has good knowledge or experience using both I am really interested in having some feedback. 

 

Cheeeers...

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Posted (edited)

I came to the exact same conclusions as you did Fred:  Stol plane = go as long as you can turn/clear.  Scimitar = little less static thrust but better cruise and smoother running.  Also does better if the tips go trans-sonic.

Edited by Yamma-Fox

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Posted

Thanks, good input..

I have a 1:2.76 reduction, a maximum RPM of 6300 , 92 HP/10.6 Kgm... 

My understaning is that  2 blades are more efficient but for 2 strokes 3 blades are prefered to avoid vibration...

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Posted (edited)

You know your stuff Fred, and I'm sure you've already run your tip speed calculations for a longer prop. But if not here's where I did mine. Make sure you use the coldest temperature that you might be flying in.

 

http://www.warpdriveprops.com/propspd2.html

Edited by Yamma-Fox

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Posted

Yes I used the same - I don't have enough ground clearance to get the tips to 0.8 mach... I did order a custom made 2 blade wood prop, got it in the early spring (read still cold) and it was great. A few months later when the French summer set in it was just turning and turning and I had to be very careful not to excced maximum RPM at takeoff. Fixed pitch is a no go here and with a 2 stroke you need odd number of blades. 

Thank you for you input - keep it comming! 

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Posted

I like the Warp drive prop speed calculator but I find it impossible to choose a prop by just looking at the prop tip speed. Different propeller blade profiles/shapes allow for much higher prop tip speeds without loosing efficiency (scimitar for example).  I also think that a prop fitted to a 2 smoke is going to be different than for a 4 banger (very different torque curves).

I would love to see a "calculator" taking into account... engine type/Hp/aircraft speed range/pusher or tractor/ prop clearance/ weight etc..   You just type in the fields and voila.....your best suited propeller comes out with a link to the best distributor closest to where you live :)

 

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Posted

But if we had that magic calculator.. would we not miss those constructive discussions? 

Btw, I have a question to anyone who already have a Luga prop or a detailed offer from them...
On the site I read
S106.thumb.JPG.54a38fe4d065b2dc00427c82d
naively thinking that "Diameter" (1750/1770/1815) is the propeller diameter... But when I get the proposal from Roman I read following:

SL106-1750mm(3-blades) propeller=580evro including shipping


width of the blade - 120mm. 
The diameter is 1770 mm (with a hub with mounting slots at 101.6 mm+20evro)

Why does 1750 mm blades make 1770 mm diameter?

Maybe just a typo, I'll get back to him...

 

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Posted (edited)

Hello,

I have found a chap who tested 2 bladed vs 3 bladed carbon fibre props for multicopter RC models.....I know this might sound stupid but remember most aircrafts have been a model before being a full size aircraft (wind tunnel testing etc)..  

The great advantage with this test is that he uses the same engine (electric brushless type) and the same propeller pitch/size for each test. It's also more precise/easy to measure electric current consumption vs thrust to determine efficiency instead of fuel flow vs thrust.

The results are in the beginning, so no need to go through all of the video. ......the winner is....2 bladed for efficiency and 3 bladed for thrust (not by much though +7%)

and here another one , not as scientific just comparing 2 vs 3 blade ..... interesting to see the 3 blade prop not so good in cruise above 70% pwr...

 

 

 

Edited by flywise

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Posted

Would the results change much in cruise with a draggy plane like a kitfox versus a slippery plane Rv?

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Posted

yes it does.  I have been flying RC planes all my life.  There is no magic bullet.  The engine and prop combo that works well on one plane may not fly for crap on another that is the same basic size and weight.  A slippery "pattern" type plane with a thin airfoil may take a much higher pitched prop with the same engine as compared to a much draggier "trainer" type plane with a boxy fuse and thicker flat bottom wing.  For one type of plane I may run a 10X5 or 10X6 prop to get the best performance for the "slippery" plane and the same engine run a 12.75X3.75 on a higher drag plane.

Doing a prop comparison on an electric engine is quite a bit easier as you can hook up the meter and see just how many more amps its pulling to get the same RPM with one prop versus the other.

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Posted

I like this picture of an aerodynamic analysis of a full scale propeller blade. Nice to see where the vortex is generated visually...

 

KDC_PROP_E_CFD__09525.1484594697.png

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Posted (edited)

Hey guys, today I received my propeller from airtrikes....here the pictures for you. The quality is very nice/excellent. I had a small damage on my spinner as it was in the box sitting on it's nose....no big deal to repair. I am saving 6.2 Lbs weight changing from my GSC to the L106 Luga (2 bladed setup / weight is 5.5Lbs)....of course I'll have a KIS fixed pitch instead of my in flight variable...

Next I will setup the 3 blade..

Interestingly on the blade it says 1770, I ordered 1750 and it measures exactly 175 cm / 69in

Next step TESTING......wahoooooo it's really christmas for me

P.s just got the 3 bladed together....weight is 8Lbs (vs 5.5 Lbs 2 bladed) and diameter is confirmed at 175 cm (same as 2 bladed)

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Edited by flywise
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Posted

Lost in translation...

Roman wrote to me : "SL106-1750mm(3-blades) propeller. The diameter is 1770 mm (with a hub with mounting slots at 101.6 mm)",
and now you say "
blade it says 1770, I ordered 1750 and it measures exactly 175 cm / 69in"... 

Very confusing.... anyway, we are keen to here you feedback on this magnificent prop, it looks great! 

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Posted (edited)

Thanks, good input..

I have a 1:2.76 reduction, a maximum RPM of 6300 , 92 HP/10.6 Kgm... 

My understaning is that  2 blades are more efficient but for 2 strokes 3 blades are prefered to avoid vibration...

As a minority (4-stroker) I am following your props critique with interest - We all learn from each other - Not mentioned is that the 3 blade had a better vibration pattern for the 4-banger 4 strokes too, although some are flown with 2-blades.  Also not mentioned, As Daryl at Warp Drive told me, " You may get same TO and Better Cruise from a 68" 3-blade with more pitch than a longer 72" prop with less pitch."  And, I think that the tapered tips may require more pitch for static than the squared tips?

 I also agree wirh akflyer - What works on a slicker Kitfox 4, or later Kitfox wings may not work as well with the undercambered wings on the other models.  Just 2 more cents worth.  EDMO

Edited by EDMO

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Posted

Hey Fred,

I have been measuring everywhere on the hub to find where this   "with a hub with mounting slots at 101.6 mm" could be. I can't find anything close to that measurement. First I thougt that 'mounting slots' means the slots where the blade shank fits into...but no.

Sorry, can't help on this one......

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Posted (edited)

Hey Fred...Hurrah

I just found that the 101.6mm makes reference to the rotax 912 propeller flange bolt pattern (the outer bolt pattern with the pressed drive lugs).........

Funny my propeller makes me remove the drive lugs and uses the inner propeller flange bolt pattern (without lugs) at 75mm..

 

Hope that helps

prop flange bolt pattern.png

Edited by flywise

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Posted

Hey Fred...Hurrah

I just found that the 101.6mm makes reference to the rotax 912 propeller flange bolt pattern (the outer bolt pattern with the pressed drive lugs).........

Funny my propeller makes me remove the drive lugs and uses the inner propeller flange bolt pattern (without lugs) at 75mm..

 

Hope that helps

 

Thanks for the followup, appreciate that! 
For the incomprehenisbile  relation between prop engaving and actual prop diameter I guess the solution is some back and forth with Roman before placing the order.
Good luck and keep us updated!

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Posted

I believe that the overall prop diameter on some propeller models is adjusted by having different shape / size prop hubs, the blades remain the same.....I do not have proof of this though, to be taken with a grain of salt.

Love mysteries

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Posted

What I'd like to know is what advantage other than noise one gets with the scimitar shape.  Is the thrust similar or equal or more for the exotic shape? Why I wonder. 

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Posted

As far as my research on the scimitar shape, I found that it runs smoother and quieter, cruises very slightly more efficiently, and has better trans-sonic properties if you were to get the tip speed above .89 mach.  Downside is that it has a little less static pull.

So I decided to go a little longer scimitar than I would have gone with a straight blade  (to regain lost thrust) that will turn with higher tip speeds... but it should be able to handle that better.

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