I found a quite interesting site:
http://www.nextcraft.com/
There was for example a 1/3 scale Berkut/Long-Ez project. 1/3 scale RC-model is said to be minimum sufficient for modeling the full scale aircraft, so I find this example quite educational. As can be seen though, the airfoils are different than on the full size plane. This is necessary because of the very low Re of the model. It does not thus model it very accurately, so there might be still surprises on the full scale version when scaling up, but I think it would still be good to do 1/3 models of new aircraft designs.
The direct link to the 1/3 scale Berkut can be found here: http://www.nextcraft.com/berkut01.html
3 comments:
Birds do not want to use canard configurations:
The Rutan canard designs are maybe "sexy" but why do I have some doubts how they fly. There was this John Denver crash 1997
http://www.asktog.com/columns/027InterfacesThatKill.html
an experienced pilot he was.
I assume that the normal configuration of controls is more forgiving for pilot errors. And we have to remember that there is no bird flying in canard configuration either. All birds have the stabilizing aft tail.
Janne.
Janne, it is not up to aircraft configuration how forgiving it is. Canard is actually easier to fly than conventional and is more tolerant to pilot errors. John Denver crash is maybe the most wrongly interpreted accident out there.
Control ergonomy in cockpit has nothing to do with the configuration. Both normal and canard feel exactly the same when using the stick & rudder, except that canard is maybe responds slower and is less agile (canard is not suitable for aerobatics).
The disadvantage of canard is in the Clmax. There are no other disadvantages than that, but that alone is a such big issue that many designers choose the larger Clmax over the better stall behavior and safety of canard aircraft, that is because canard aircraft can not use flaps (unless one invents a flap configuration that does not increase pitching moment).
Canard configuration becomes more efficient as the canard size increases until it reaches tandem wing. Tandem wing is almost as efficient (without flaps) as conventional (with flaps)
Rutan's reasoning for using canard in the EZ-type aircraft was because of safety. Large amount of accidents are stall/spin accidents. These do not happen with canard aircraft as they are stall resistant by definition and spin proof. Long-Ez may look like it would be a jet fighter, but the looks can be deceiving - Long-Ez looks like that because Rutan wanted to have low drag (high efficiency) and at the same time stall and spin proof design. Long-Ez was quite successful at its time, 25 years ago.
I felt I should comment. Canards properly designed and operated are in some respects safer than convential configurations. Notably the resistance to Stall Spin incidents.
Having said that there are a number of things which if designed poorly can result in a worse high alpha behaviour. The wrong combination of aerofoils and angles of incidences for example.
Birds are an interesting example for comparision, this comparision would suggest that we should not fly any aeroplane as we do not have fully variable geometry wings.
This issue of stalling and other issues is resolved by mother nature spending the last few million years evolving the Bird Flight Computer, this investment in wet-wear allows birds to operate unstable, geometrically variable airframes at high angles of attack successfully (most of the time).
There are incedences where the Canard configuration has disadvantages, most of which revolve around high CL operation, such matters as the difficulty of providing effective flaps and getting the main wing to operate close to the stall means that such things as short field performance will always be a little poorer than the convential configuration.
Birds are interested in landing on branches so operating at the stall is the norm for them, watch a sea gull land in a small area and you will often see some of the small feathers disturbed on the inboard wing (stalled).
Now to the point in a previous post which I felt I should comment on, the subject of the last Mr. Denver, he was an experence pilot with as I understand it approaximatly 2500 flying hours. The NTSB report does not fault the pilot, but puts the probable cause down to Pilot distraction, one should read the report http://www.avweb.com/other/ntsb9905.html
Not the aeroplane.
I think that Mr. Bert Rutan would say that he does not need defending; he is in my opinion one of the most talented aircraft designers we have seen todate; his aircraft are very soundly designed and when built and operated correctly are very safe.
Lastly the selection of an airframe configuration cannot be based on birds, they evolved to solve different problmes, it must be based on what the aeroplane is to do.
As for the suitablity for aerobatics, it depends on the aerobatics in question, competition aerobatics perhapse, but aerobatic aeroplanes are regularly provoked into doing things Canards are designed to prevent.
Clear Skies
Cliff
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