Jt11

[jucie]

What do you think of Jukka Tervamaki's new project?

JT11 project page (http://www.icon.fi/~jtki/jt11virtual.html)

[bowns]

A few were built but seems no comment yet,far as i know.I enjoy the idea of engine behind the mast.
Sory,wrong information.A mix-up with TJ-9T which is a single tractor.

[gyroblackwell]

I have been in contact with Jukka for a couple of days now. This is a brand new design with no prints or anything built to date. He's a great person to chat with .... very helpful.

I let him know that I would like to build this design as soon as I have my ultralight up and flying. He will be supporting my efforts!

I would like to try using a Mazda RX8 rotary motor with a reduction system that I saw used on an RV4.

I also would like to make the outer skin composite.

I am modeling up the chrome moly frame using Unigraphics CADD package.

I have the basic over-all dimensions, and a few views of the current design.

[quadrirotor]

I am back after the crash of my hard disk, twice in a year!...but this time i lost many things... :eek:
The JT11 is a winner, i dreamed it and Tervamaki made it... :p
Thanks to Mr Tervamaki; all it needs, may be, is a four blades rotor! tip-jets... :)
The cooling of the VW engine could be done efficiently with the use of a shrouded (turbine) fan:
http://www.hotvws.com/search.ihtml?cmemstep=5&searchsub=1&sqlview=7&make=Gurgel

[Victor Duarte]

I saw this design some days ago.
this concept looks familiar to me.. :D
the idea of the engine behind the mast is not so bad..but the visibility gain, in this case, is not very remarquable.
Thank

[Rotor Rooter]

There has been some discussion reciently about the use of 4-blade rotors. Both teetering and articulated/hingeless rotors have been discussed.

What advantage(s) would there be for having a teetering rotor with more than 2 blades?


Thanks.

[Victor Duarte]

You're the rotorman Dave, you should answer (i guess you have the answer)

[quadrirotor]

Dave, i can't access my posts earlier than the 500° past post... but i kept some of the arguments (03/2004):

"The performances and efficiency are documented:
Boyette: Rotocraft dec-jan 97-98 p.44.
Magni: Rotocraft dec-jan 00-01 p.27.
and others...
conclusions: better efficiency, better lift, less drag, less (no) vibrations, better flares, stiffer and cheaper blades, less fatigue, better sound and so on etc...
The scisor effect is not well documented, it seems not to be a big issue for semi-rigid rotors.
Sportcopter solved this problem that exists even with two blades rotor...

Price:
Sportcopter 25' 7"----> 1700$ X 2 = 3400$
Sportcopter 30' 8"----> 3900$ X 1 = 3900$

500$ cheaper with four blades! ok use them to have a heavier and more complex rotor head...
and to improve this rotor, you must add some power to the rotor: the BIRD of Dick Degraw---> 90mph cruise on a ea81 stock!...(10% power on the rotor)
and Bensen has done it before!...

AND TO HAVE THE BEST GYRO CONFIGURATION:
to slove the C.G. problem put the engine behind the seats but the prop in tractor position..."

[skyguynca]

That about covers it.

[skyguynca]

Oh I have seen this design and talked with him often by email. Great guy and very very good engineer. I have alot of his plans too.

[Rotor Rooter]

quadrirotor, Thanks.

The Magni rotorhead is interesting. I suspect that there is a little more going on in the head then what can be seen from the one picture. Unfortunately, I don't have the Rotorcraft Dec/97 - Jan/98 issue.

Thanks for mentioning the perceived advantages. It would appear, to me, that some of the conclusions they have reached might be a little dubious.

By the way, I agree with your earlier comment. After a couple of weeks of R&D, it became apparent that the most efficient route to a new helicopter is not via the gyrocopter. One (or both) rotor heads will be developed on a helicopter.
____________________

IMHO, a rotor with more than two blades, PLUS a pitch/roll coupling between the rotor disk and the fuselage, should increase the control, stability and safety of a gyrocopter. There is the obvious lead/lag problem to be solved.

However, perhaps this subject should be left for another thread at another time.

Dave J.

Edited

[Dean_Dolph]

I posted info about the 'DeBird I pulled out of an issue of the PRA magazine in another thread.

In that article, Dick DeGraw commented that he tried several rotor blade combos including multi bladed ones and ended up using two blades because apparently there wasn't enough of an advantage to use the multi blades and the two bladed DeBird makes for easier hangaring. In this case the KISS principal was applied.

[Victor Duarte]

This imput is very very usefull Dean. Do you know where i could read more about Mr Degraw's opinion on multi-bladed rotors ?
thank you

[Dean_Dolph]

Victor, the info out of the article is all that I know about. Dick doesn't go out of his way to make presentations or make himself visible. But hey, maybe Tom Milton can get him to do a presentation at Mentone '05! I know that won't do you any good now but it would still make for an interesting Mentone forum.

[quadrirotor]

Ernie Boyette is preparing with Dick Degraw a three bladed rotor!...
It's not a question of opinions but of facts...facts given by tests discribed in the articles cited above and calculations:
tests => comfort, performances, etc...
calculations => about 5% to 15% better for 4X25'X7" compared with 2X30'X8.25"...for a RAF, 1330lbs, 80 mph, ASL, drag=140lb vs 160lbs, L/D rotor only=9.5 vs 8.3...
construction=> stiffer, cheaper blades, easier to manufacture, to balance, etc...
storage => the same (or even better 25'vs30'), with folding blades...

[Victor Duarte]

stiffer, cheaper blades, easier to manufacture, to balance, etc...
storage => the same (or even better 25'vs30'), with folding blades...
Andre, i'm not shure the gain is really there.
a 3 bladed rotor doesnt really shorten the blades ( 1.5 ft less perhaps ) , it make the blades thinner so MORE difficult to mfg. a 6 bladed rotor is not easier to balance. I want to see it
i want to see the folding blades

i hope i can go to mentone.

Dean, thanks anyway

[jucie]

Thank you, guys, for the answers.

I am a big fan of Jukka's work, but this idea I didn't bought yet. I think the long drive shaft isn't worth the trouble. Maybe an hydraulic (http://www.rotaryforum.com/forum/showthread.php?t=3498) transmission could be considered as another choice.

[jucie]

The cooling of the VW engine could be done efficiently ...

Andre, that VW is just to show an engine, because Jukka didn't have another engine model at the time to fit in his drawings. The final engine will not be an air cooled VW.

[quadrirotor]

Jucie your are right twice:
-Yes the weakest point of the project is the drive shaft...dead weight...and technical problems to have a dependable solution...so i recommanded the EGGOCOPTER, that's a two tandem engines (futhermore: two 50 hp engines give more thrust then a 100 hp!...); but this does not mean that the Jurka's project is foolish...
http://www.rotaryforum.com/forum/showthread.php?t=2191&highlight=eggocopter
-Yes for drawing purposes, Jurka used the VW engine model...But for me the VW engine has many advantages, and can be used with a good cooling, like in the Porshe configuration!...
-My first choice remains the Barnett J4B2, with a offset hinged quad-rotor, with a prerotator and IFAP consisting of tip-jets feeded with a turbo (compressor) which is plugged in the engine...

[Victor Duarte]

Andre,
Would you by one if it flies ?
thanks

ps : where can i see an offset hinged quad rotor flying ?

[quadrirotor]

Victor:
Of course! (depending on the price!)
Quad-rotor=four bladed rotor.

[Victor Duarte]

Andre, yes, i understand four bleded, but where can isee one flying ?

at whitch price do you estimate a such aircraft ?
thanks