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New Propeller - Snake oil or factual

DonFromTX

DonFromTX

Well Known Member
I had quite a chat with these people at Oshkosh, they believe they have redesigned the airfoil on a prop to give the same efficiency as a constant speed prop! No changing of the pitch or bending blades, just aerodynamics, wonderful on a RV 12!
Does anyone have any knowledge of the company or its products?
http://www.duc-helices.com/anglais/index.php
 
Relatively easy to have a gorgeous website, photos, etc and a booth at KOSH. Not so easy to make a revolutionary prop. I'd wait until there are a hundred or so "beta-testers" flying before I reached for the wallet...

Only time will tell, but we can always hope, right?
 
j'ai tres confused! n'ece pas?

okay, sorry, only took 7 years of French.....lotta good that did me.
nice website, pretty props, but sheesh, can they have some grade 4 do spell-check? It's hard to know what the heck they are trying to convey!
...doesn't seem to be much about the 'constant speed' prop that I could see.

Didn't Aeromatic do this in 1935? :) anyone have a link to the real goods?
 
I had NO french, so talking to them was a problem as well. This is no Aeromatic type system, no blade change at all, the effect comes just in the shape of the blades.

flyboy1963 said:
okay, sorry, only took 7 years of French.....lotta good that did me.
nice website, pretty props, but sheesh, can they have some grade 4 do spell-check? It's hard to know what the heck they are trying to convey!
...doesn't seem to be much about the 'constant speed' prop that I could see.

Didn't Aeromatic do this in 1935? :) anyone have a link to the real goods?
Click to expand...
 
This propeller was studied to have an " constant speed " effect. The blades are manufactured with part of carbon plies and their design was carried out to obtain maximum strains in torsion and inflection. It's why the constant speed effect is not dependent on the blade distortion but on its geometry and its particular profile.

Because of the extra flat profile and a small cord, we obtain an excellent output as well:

In performance,
In noise
In consumption.


ADVANTAGES
Thanks to the " constant speed " effect, we have very little variation ot the RPM engine between static and dynamic.
This propeller makes it possible to have more performances on the whole of flight to knowing :

Better effectiveness on the takeoff and in rates of rise due to the engine speed more raised
much lengthening-piece in cruising,
A great comfort of use
 
French

ADVANTAGES
Thanks to the " constant speed " effect, we have very little variation ot the RPM engine between static and dynamic.
This propeller makes it possible to have more performances on the whole of flight to knowing :

Better effectiveness on the takeoff and in rates of rise due to the engine speed more raised
much lengthening-piece in cruising,
A great comfort of use

Can someone translate this into English for me Please!!
 
Gosh you are pretty close, why don't you fly over there and check it out for us?

WAM120RV said:
ADVANTAGES
Thanks to the " constant speed " effect, we have very little variation ot the RPM engine between static and dynamic.
This propeller makes it possible to have more performances on the whole of flight to knowing :

Better effectiveness on the takeoff and in rates of rise due to the engine speed more raised
much lengthening-piece in cruising,
A great comfort of use

Can someone translate this into English for me Please!!
Click to expand...
 
WAM120RV said:
ADVANTAGES
Thanks to the " constant speed " effect, we have very little variation ot the RPM engine between static and dynamic.
This propeller makes it possible to have more performances on the whole of flight to knowing :

Better effectiveness on the takeoff and in rates of rise due to the engine speed more raised
much lengthening-piece in cruising,
A great comfort of use

Can someone translate this into English for me Please!!
Click to expand...

This English seems perfect to me, both syntactically and grammatically. May be you have to realize that there are smart guys in aviation all over the world, not only in the UK. :rolleyes:
 
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Which propeller is this? The "Swirl"?

Looks like the company itself has been around a while, and seems they have a variety of products in active use. Seems mostly non-US.

SportAir seems to be the US outlet: http://sportair.aero/category/4-propellers/ ...maybe ask them their thoughts. Also a better written English writeup on the Swirl prop on that page...linked to from the DUC site.
 
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I THINK I got Jan and him tied together enough, that they are sending him a propeller to put on his RV12 and try it out. Language barrier again at play. They seemed quite interested in that market.
 
Evidence and interpretation

It is inescapable for "well-designed" fixed-pitch propellers to see a change in power absorbed with speed- which leads to the change in RPM for fixed throttle position.

If the RPM does not change much with speed, it suggests to me that it is an unusually bad design, not an unusually good one. It suggests that the bulk of the power is absorbed by profile drag rather than induced drag.
 
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Years ago, wooden props were often made in a scimitar shape with the idea that when you climbed, the blade would twist flatter. When you cruised, it would increase pitch.

I don't know that this effect was ever actually documented in rigorous testing, though.

Dave
 
aeroelastic effects...

....do change the propeller shape as a function of RPM and loading. In fact it is difficult to design a propeller well unless you can account for that, or else just make it really stiff.

Especially with composites, the possibilities of designing a prop that to some extent compensated for speed correctly are quite good, but in this particular case, the CLAIM is that it is due to some magic airfoil, not because of twist change. (at least that's if I read the claims right)
 
Actually, the DUC prop is for real and leading edge technology in propeller and airfoil design. I heard about this prop coming into production and attended a couple of theory presentations from the designers. IMHO, It is for real, and extremely innovative.
 
I'd be careful about underestimating how clever some small Western European engineering shops can be. From Scandinavia, all the way south through France and including Germany, cutting edge technical competencies and clever manufacturing both abound.

As for the limited English capability, that's just a French thing. Our British cousins, in many cases, have actually learned to speak a Continental language or two and so aren't too bothered by that inconvenience. Something we might learn from...

Jack
 
Uk

What I will do is try to find out whether anyone is using this prop in the Uk.

As for the Frenglish its almost as bad as some of the signs i have seen in china translated directly into English but reading as Chinglish!! I take photgraphs of them now so i can have a laugh when I get home.

It is though joking apart really annoying when someone has what appears to be a good product but fails on the marketing or that product in other countries by leaving the translation to someone not up to the job.

Actually I have just remembered a couple of my friends are flying to the RSA rally in early September, I will ask them to search out some information there.
 
Jack Tyler said:
I'd be careful about underestimating how clever some small Western European engineering shops can be. From Scandinavia, all the way south through France and including Germany, cutting edge technical competencies and clever manufacturing both abound.

Jack
Click to expand...

One look at Pipistrel, TL, etc, and you can clearly see the cutting edge technology in carbon fiber and aerodynamic efficiency design. DUC Propellers have been around for 15 years and are a great prop in Europe, not much marketing here, but that may change with this new prop. Clearly, the US is lagging.

http://www.pipistrel.si/

http://www.duc-helices.com/anglais/windspoon.htm
 
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We would appreciate any user feedback you can obtain. It is pricey, and requires you to send it back to France every 800 hrs as I recall, but if it does the job it would be worth it to me.
 
Jack Tyler said:
I'd be careful about underestimating how clever some small Western European engineering shops can be. From Scandinavia, all the way south through France and including Germany, cutting edge technical competencies and clever manufacturing both abound.

As for the limited English capability, that's just a French thing. Our British cousins, in many cases, have actually learned to speak a Continental language or two and so aren't too bothered by that inconvenience. Something we might learn from...

Jack
Click to expand...

very true jack!

don't discredit the french just for their language problems... upside is their younger generation is doing much better with speaking english now, it's mainly the older and middle-aged "grande nation" generation that is actively rejecting english as the international language of choice and will not hide this sentiment ;-)
not knowing much about DUC h?lices, what i can tell is that they're not a new kid on the block and have been around for a long time on the european market, mostly on the low and slow end of the market, with a credible reputation.

also, a lot of european products never make it to the u.s. because they are developed on a "good isn't good enough" basis, which obviously results in much higher production/acquisition costs. and obviously, support, sales, legal issues etc... all need to be handled somehow. hence few companies appear as their own self but rather through some rep/distributor in north america.

don't get me wrong, i also enjoy the more competitive u.s. market (shopping, buying airplane stuff, travelling) and the "designed to get the job done" attitude makes an awesome kitplane like an rv affordable to a broad audience, including me. van's definitely has struck a very nice balance and produces an excellent kit. and the "economy of scale" aftermarket advantages (think classic aero interiors as an example) are grossly underappreciated yet by many potential builders evaluating kits IMHO.
yet the swiss in me cried many times why some parts of the kit didn't receive just a little more attention to design or quality... ;-) tipup hinge/frame comes to mind, among a few other areas.
at the same time, a lot of european designs/kits have died in beauty because they simply turned out too expensive and suffered from poor customer service.
the same cultural variations have really shaped the engine market it is today (in the lycoming power range).

applied to the french prop discussion, give them at least a serious look...

and to the future of van's i wish them a bit more of swiss engineering, some japanese production/quality control and continued great u.s. customer service. as everyone else, i'm very interested to see what their next move is...

greetings from a swiss perfectionist with some serious american mindset implanted ;-)

regards, bernie
 
I have an aviation magazine from the 40's that my dad gave me. There is a photo and short article about a 1 bladed propeller that had been developed. It had a single blade on one side of the hub, and a small counterweight on the other. The hub was designed to allow the blade to change pitch angles due to load speed etc. It was fully automatic, and not adjustable from the cockpit. The claimed advantages were the adjustable pitch and that the single blade was more efficient. The down side was cost and that the single wood blade would absorb moisture and become unbalanced since the counterweight was metal.
 
Mark Henderson said:
I have an aviation magazine from the 40's that my dad gave me. There is a photo and short article about a 1 bladed propeller that had been developed. It had a single blade on one side of the hub, and a small counterweight on the other. The hub was designed to allow the blade to change pitch angles due to load speed etc. It was fully automatic, and not adjustable from the cockpit. The claimed advantages were the adjustable pitch and that the single blade was more efficient. The down side was cost and that the single wood blade would absorb moisture and become unbalanced since the counterweight was metal.
Click to expand...

A one bladed prop is the most efficient. You would get some really strange looks on shut down huh?
 
I have recently been studying the propeller blade thing, one, two, three, four or five blades. Some really interesting and very deep stuff. Some of it suggests that the Rotax SHOULD have a three blade prop. I personally prefer a five bladed prop, solely for the fact that it looks so darned cool:D
 
Just a note about RPM change in FP

scsmith said:
It is inescapable for "well-designed" fixed-pitch propellers to see a change in power absorbed with speed- which leads to the change in RPM for fixed throttle position.

If the RPM does not change much with speed, it suggests to me that it is an unusually bad design, not an unusually good one. It suggests that the bulk of the power is absorbed by profile drag rather than induced drag.
Click to expand...


Lonnie Prince makes some props that twist as they cone forward with greater thrust. This has the effect of reducing the RPM range. He says the pitch change can be 2 to 3". I have observed this on my own RV. My Catto has a 500 RPM range and my Prince had about 300-350. Performance was not hugely different. The Catto had been adjusted by Craig to produce 2650 RPM at full throttle at 8000', which is what I wanted. The first version over-rev'd. The Prince also over-rev'd and I don't have the second one yet.

My point is just that this effect can be designed into a prop. That said, the one in question here is saying it doesn't twist. That makes no sense to me.
 
About 1 blade.

Geico266 said:
A one bladed prop is the most efficient. You would get some really strange looks on shut down huh?
Click to expand...


I respectfully disagree. If blade length is limited (a very common situation) then there are a number of factors that are at work. One of the most relevant is aspect ratio because that is a big factor in induced losses. Keep in mind that props operate in a speed range where induced is a big portion of the total drag on the blade. A greater number of blades allows a narrower chord when diameter is a constraint and power is a constant in the design goals.

He would explain it differently, but even Paul Lipps appears to agree that multiple blades can be more efficient.

That said, I enjoyed meeting you at the "beer tent"!
 
Twist change....

Yes, I agree. See my post #15.


hevansrv7a said:


Lonnie Prince makes some props that twist as they cone forward with greater thrust. This has the effect of reducing the RPM range. He says the pitch change can be 2 to 3". I have observed this on my own RV. My Catto has a 500 RPM range and my Prince had about 300-350. Performance was not hugely different. The Catto had been adjusted by Craig to produce 2650 RPM at full throttle at 8000', which is what I wanted. The first version over-rev'd. The Prince also over-rev'd and I don't have the second one yet.

My point is just that this effect can be designed into a prop. That said, the one in question here is saying it doesn't twist. That makes no sense to me.
Click to expand...
 
Hahaha. It looks like this manufacturer really thinks home builders are naive and by going to Oshkosh he shall sell some of his stuff to the crowd before heading back to the other end of the world. I had a good read at your posts, then found this: http://www.love4aviation.com/Equipment/Propellers/Service+Bulletins.html

Apparently French people have had enough of this manufacturer. So now "Duc" is trying here with a bigger market and people who don't know about the in-flight breakage of their propellers, lack of customer support (language barrier doesn't seem to be the real problem), no quality assessment etc.

My understanding is that the Warp Drive is better than the Swirl in term of quality and customer support, performance are the same. The "constant speed effect" seems to be a marketing stunt.
 
Why not??

DonFromTX said:
I THINK I got Jan and him tied together enough, that they are sending him a propeller to put on his RV12 and try it out. Language barrier again at play. They seemed quite interested in that market.
Click to expand...

Might as well. You've got an unproven engine, why not add an unproven prop?

Don, you are really testing fate!!!

It hurts to see people get guided down this path with very predictable results. Sorry to be blunt, just tired of seeing people lose thousands of dollars, crash planes, with some paying the ultimate price.
 
And it hurts me to have someone who seems to have all the answers, and is certain that nothing new can ever be developed, and "unproven" automatically means dangerous.
I would bet you have not a single Viking powered aircraft incident, nor any propellor statistics from this maker. I guess I have been around too long, "Experimental" used to have a good meaning.
 
DonFromTX said:
I would bet you have not a single Viking powered aircraft incident, nor any propellor statistics from this maker.
Click to expand...

Don,
I think Darwins point is, that because there is only a few Viking engines flying, and no to very little reliability data available on the propeller, equipping a new airplane with both would be configuring a new airplane so that it was operating at the fringe edge of "Experimental" (in the amateur built category anyway),and all of the additional risks that go with that.

I would say that I agree.

You are right. The experimental category is all about experimenting. But often people are a bit naive as they cross into a much riskier part of it ( I am not directing that comment at you specifically Don, just speaking of the home building community in general). I think it is important for those of us that have long term experience, pass along the gained wisdom to others.

In this case I would say the message is... "Just because a company has a nice looking web site and is willing to take your order", doesn't mean it is a proven or safe product. As long as someone goes in with eyes wide open, and is aware of the risks and realizes that they are actually doing testing for the manufacturer(s), I say go for it.

The problem is that very few people who purchase the next new promising ___________ (fill in the blank) are aware of that, even though I would bet that the majority of the people that participate in this forum have no desire to knowingly put them self in that position.
 
This attack was in response to my comment of having paved the way for an engine developer to try it out to see if it was really snake oil, nothng about my trying one out.
I am sure you would agree that if everytime someone mentioned the Rotax/Sensenich combo, there was a string of stuff about broken crankshafts, engine mounting bolts falling out, Bing floats sinking, gascolator overheating, sprag clutches failing, fuel pumps failing, and even the Sensenich prop hubs machined wrong, and the fuel tank spraying you with gasoline in a hard landing, it would simply not be productive. Look at the pile of AD's on certified planes for example. Lets just get along, have a positive look at problems and look for solutions, is that asking too much?
 
In the spirit of a gentlemanly discourse..................

Ok boys, let's see if we can keep this discusion objective, and not let it get so personal that it gets shut off! I would like to make a point based on many years in the computer software development business.

If you can possibly avoid it, never make more than one change at a time. Because, if something doesn't work just right, you won't be able to tell which change is causing the problem. I believe that principle applies in this case. Nothing against experimentation, or this particular engine or propellor. It's just that I would want to see some time put on one new system, before introducing another into the mix. No matter what the application.
 
In reading this forum, I see a lot of bickering and arguing about new design and how it may apply to what we use now. I only saw one response that referred to asking real experts (prop manufacturers) what they thought of a new design. If no one tried something new, Craig Catto would never have developed one of the best products on the market. (My opinion) Wouldn't you think he may have experimented with the same type of design after reading or seeing it and redesigning his own props if there was a distinct advantage? Anyway as far as engineering is concerned, remember that the Titanic was designed by "Expert engineers". LOL
 
Pilot Error!

And the Titanic went down because of pilot error, not faulty design! Knowing the ice field was there they should have diverted south. They should also have reduced speed. They did neither because they were in such a hurry to get to New York. Lessons for us.
 
Cato three blade prop

If I had a finished and flying 12, I'd be begging Mr. Craig Catto to produce a 3 blade prop for me. It's purely subjective but I really like to look of a three blade prop - nothing complicated here. Hope that there will be a Catto 3 blade available by the time that my 12 is completed - also hope that Van's will be offering it as part of the finishing kit. Dream on???:cool:
 
For reasons I don't profess to fully uderstand, two bladed props and PSRU do not get along well at all. Think of all the gear reduction units, most have had more than 2 blades. The RV12 is somewhat of an exception. The Viking for instance does not recommend using a two blade because of this. The one at Oshkosh this year that flew up with a two blade prop has now changed to a 3 blade. Might be somethig for Vans to investigate further, and certainly something for thinkng owners to try out. I too think they look cool!:)

E. D. Eliot said:
If I had a finished and flying 12, I'd be begging Mr. Craig Catto to produce a 3 blade prop for me. It's purely subjective but I really like to look of a three blade prop - nothing complicated here. Hope that there will be a Catto 3 blade available by the time that my 12 is completed - also hope that Van's will be offering it as part of the finishing kit. Dream on???:cool:
Click to expand...
 
Seen before...

...in a previous post. Good looking Sensenich 3-blade mounted up on a 12.

i-mkj96Lk-M.jpg


An update on this installation regarding performance would be interesting.

Tony
 
AlanTN said:
And the Titanic went down because of pilot error, not faulty design! Knowing the ice field was there they should have diverted south. They should also have reduced speed. They did neither because they were in such a hurry to get to New York. Lessons for us.
Click to expand...

Just as in many airplane accidents there were several things that contributed to the sinking. It appears that there were questionable decisions by the captain but that is not enough to account for the severity of the accident. There is a very interesting modern analysis available.

http://www.writing.eng.vt.edu/uer/bassett.html

The Rivets. The wrought iron rivets that fastened the hull plates to the Titanic's main structure also failed because of brittle fracture from the high impact loading of the collision with the iceberg and the low temperature water on the night of the disaster. Figure 2 shows the Titanic during her construction, with the riveted hull plates of her stern visible. With the ship travelling at nearly 25 mph, the contact with the iceberg was probably a series of impacts that caused the rivets to fail either in shear or by elongation [Garzke and others, 1994]. As the iceberg scraped along sections of the Titanic's hull, the rivets were sheared off, which opened up riveted seams. Also, because of the tremendous forces created on impact with the iceberg, the rivet heads in the areas of contact were simply popped off, which caused more seams to open up. Normally, the rivets would have deformed before failing because of their ductility, but with water temperatures below freezing, the rivets had become extremely brittle.

A lot of this is very familiar to those who read aircraft accident reports. A chain of events, conditions and a lack of materials and construction understanding were all important.
 
"FSTexan - Join Date: Nov 2011 - Location: x - Posts: 1"

Please consider the source when someone revises a dead thread with inflammatory info... Please do not feed the trolls.
 
DonFromTX said:
Could be. I was not there and still have problems even visualizing the action that did all that.
Click to expand...

An almost 600 FPM decent at just shy of 90 kts, is what the EFIS recorded a second or two before ground impact, with a very abrupt pull-up just before impact, is the action that did all that.
 
I would guess the Wright brothers are top on your list of what hurts you. Unproven engine, unproven prop, unproven PRSU, and unproven airframe! History seems to disagree with you.

RV7Guy said:
Might as well. You've got an unproven engine, why not add an unproven prop?

Don, you are really testing fate!!!

It hurts to see people get guided down this path with very predictable results. Sorry to be blunt, just tired of seeing people lose thousands of dollars, crash planes, with some paying the ultimate price.
Click to expand...
 
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