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Old Jul 22, 2010, 02:00 AM
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Yeah, I noticed the triangles too, all the larger TAF's seem to have them, my guess is thay are simple sprayguards. As we have seen, the CG is lying very far in front, so the clearance between the leading edge of the front wing and the water won't be very large during Take off, I guess

Here they can be seen(drawings come from the TAF company, sideview and upview don't belong to each other)


Or on this 9-seater:


I still guess that it's a sort of preliminary design model for the TAF-4, take a look:



The only thing that isn't the same as on the model is the rear wing.

About the linkages, you're right, they seem to be linked internally. The 2, 4 and 9 seater had them external:

2-seater:




And here you can see the rudder of the 4-seater, with it's linkages external:


Even the 9-seater, hard to see but definately external:


Cool machines!

Marijn
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Old Jul 22, 2010, 03:52 AM
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BTW, this is an intersting drawing, it comes from a presentation Mr Jörg gave a few years ago. It gives the basic principles for positive stability on Tandem WIGs



It shows the difference in wing profiles, and how the rear wing isn't just a copy of the front wing.

Marijn
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Old Jul 22, 2010, 06:27 AM
TheyreComingToTakeMeAway!
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whats interesting to me is that the prop has a clear downthrust to it. i wonder if this is to alter the pressure under the rear wing or help lift the nose? it doesn't quite go through the cg however so i dunno...

and as for the "linkage" i just meant that it has one and you can see it is going into the fuselage/hull so maybe it had a large servo in it for running it
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Old Jul 22, 2010, 04:14 PM
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Haha okay, I don't know what the purpose of the yellow model was. On a ZDF documentary some years ago they showed Jörg, standing by the side of the pont, with an RC model of a Tandem WIG, it was yellow, so it could be this one.

I don't know about the down thrust either, the drawings probably aren't all as accurate, so it could be that the thrust line runs straight through the CG.

Crashed my Robbe Commander today on the second test flight, it showed strange rolling characteristics, I first thought it had to do with the electronics, but during the second test flight I found out that it was just really tip stall sensitive. Before I managed to land it safely, I turned into the wind to final and snapped it out of the turn, it flipped nearly upside down in half a second and went vertically into the ground

Nice design(NOT), it is very old, it dates back to 1997, but I didn't think its flyin characterics would be that bad. Anyway, I am now reviving my Twin star and the Tandem model had been put on ice for the next days.

Marijn
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Old Jul 22, 2010, 07:17 PM
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cool

does it have flaps? and elevator?
Quote:
Originally Posted by hoverman View Post
I found some nice pictures of what I believe to be windtunnel or test models of the Jörg company. The White model seems to be an older model, the hydrodynamics seem to bee simpler and less worked out. The other model looks like a scale version of the TAF 4, the largest one with a turboprop.









Marijn
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Old Jul 23, 2010, 01:45 AM
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No!!

Tandem wing WIGs use special aerodynamics to provide a very good Longitudinal stability in Ground effect. However, this stability only works for a small range of pitch angles and flying heights, a Tandem wing WIG is under no condition able to perform a stable normal flight.

To stay within this very narrow flight envelope, these crafts never have flaps and elevator. This also simplifies the certification, as it really makes it a boat.

The only tandem wing WIG I have found with an elevator is the one from Universal hovercraft and I believe that that one was trimmed..for out of Ground effect flight, like a Tandem aeroplane, and is flying very low to use Ground effect(not quite the same). In the video it can be seen flying higher than usual and also up 20 degrees pitchup, which I believe is way beyond the stable pitch up range for the real Tandem WIG boats designed by Gunther Jörg.

Greetz,

Marijn
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Old Jul 23, 2010, 09:13 AM
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So tandem wing config could work better than I tought, just the airfoils and angles are more critical.


But still I can't image how could they build a manned craft without horizontal controll surface. It doesn't need it, but what about a dangerous situations? For example bigger wave strike or wind. And what about slight CG changes (fuel and payload)?

As far as I know the 12-seater Flairliner TAF is the bigges commercial WIG ever built (and the most fancy http://www.airfoil.de/uploads/pics/foil7_.jpg ).

gabriel
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Old Jul 23, 2010, 04:08 PM
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Well, I thought building these machines with 12 passengers was sheer madness, but what my nonRC model currently shows is this:

- If you throw it the wrong way, which means it bumps into the street immediately after you let it go, it will leave the ground effect zone in a very graduate way, about 10-20 degrees pitchup, then slows down, stalls, and plunges back to the ground, without any further pitching up.

- If you throw it right, it flies at a maximum of 1 cm( actually you can hardly see it fly, but you don't hear skidding), it is véry stable, nomatter which speed you throw it at, it shows absolutely no pitching whatsoever. Even if it skids into rocks, it changes cours or slips a bit, but it still won't do something dangerous

So, yes, you don't have a stabilser with elevator, but I must say that the model is..quite safe. I even wonder whats safer, the Lippisch does have the ability to return to Ground effect on its own, but it flies easily out of Ground effect(small gusts etc.), it constantly changes it pitch attitude(also by small gusts), and it clearly shows different handling when the speed changes.

I don't know, I just have to say that allthough I have criticised it much before, I would easily trust the concept enough to build a model of it to be used on water.

BTW, here are two larger photo's of the 12 seater, quite a machine!



Enjoying your vacation?

Marijn
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Old Jul 23, 2010, 06:09 PM
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I'm looking forward to the RC version of your TAF.

By the way I found 4 high res. photos about the Wigetworks Airfish 8 -001. It has the 001 designation since March when it was successfully registered as a ship in Singapore, and it was Christened in April

http://www.flickr.com/photos/acroama...57691/sizes/o/
http://www.flickr.com/photos/acroama...n/photostream/
http://www.flickr.com/photos/acroama...n/photostream/
http://www.flickr.com/photos/acroama...n/photostream/

Gabriel

ps: Absolutely Unfortunately yesterday it's over. But you know... home sweet home.
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Old Jul 24, 2010, 02:32 PM
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Cool photo's, looks like they made quite some small changes to the airframe, for example, it now seems to have a sort of sprayguard or something on its nose, infront of the cockpit window.

I don't know if and when I'll build an RC tandem, I am going on vacation too in a week, for two weeks. However, I did make a pair of Tandem wings today, with slightly thicker profiles and chords of 30cm, maybe I'll use them on an RC model.. lets see

Marijn
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Old Jul 24, 2010, 04:34 PM
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Chords of 30cm or span of 30cm?

from your testing, which kind would have a lower flying speed, the tandem or the lippisch, given similar weights and such?
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Old Jul 25, 2010, 04:06 AM
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I decided to build another non RC model first, 1:1 size of the possible RC model.
The chords are 30 cm The span is 50 cm, the distance between the wings 15 cm.
I wanted to test if the same stability can be reached when the wings are placed closer together, and the angle of attacks are higher( wich usualy enhances the pitching moments).

The front wing has an angle of attack of 9,5 degrees, the rear wing 6 degrees. I increased the angle of attack difference between the wing pairs, to enhance the static longitudinal stability, aircraftwise. This was to see if it would reduce pitch up tendencies when flying out of GE.

Also the wing profiles are thickened

It's quite a large and heavy model, I'll post pictures lateron. I did do some throws yesterday evening, and it proved to work even better than the previous model

Ow and, which one flies slower? Till now the Lippisch is definately slower, but the amount of weight I had to put on the nose of the tandem to get the CG right, makes it a much heavier model, so the results aren't very comparable. Still I do think that the Lippisch is the better performer.

Marijn
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Old Jul 25, 2010, 05:36 AM
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Here are some pictures, as can be seen it's quite large. I tested it again, it flies véry stable, even better than the previous model. It remains stable, even if it hits a stone for example.

If you throw it too hard, and it flies out of GE, it will gradually climb, stall and fall back to the ground, just like the smaller model. So, the larger Angle of attack difference didn't make ik a lot more stable, it didn't make it worse either.

Reading into some older documents I found that the TAF Flairboats didn't have actual positive longitudinal stability either out of GE, so I guess there's no use chasing this coal, even Jörg didn't manage to achieve this goal. Instead, I found that all the things, meant to improve stability out of ground effect, made the GE stability itself even better, the model is very stable, trustworthy, it flies very..relaxed

Give it a nice throw, it will glide in a straight line, 1-2 cm above the stones, not a single degree of pitching or rolling, gradually slipping sideways during stronger wind gusts.

BTW, the speed is lower than on the previous model, so the larger Angle of attacks payed off.






Greetz,

Marijn
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Old Jul 25, 2010, 06:53 AM
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hmm, so the tandem has more natural stability, but the lippisch can fly higher and slower but has roll coupling issues...

however, the tandems that have 2 props up front can start off slower as its a "blown" ground effect until the wings make most of the lift
maybe put 2 small motors in the nose of the tandem and connect a servo to the mounts on the elevator channel so you hold full "up elevator" to blow the motors under the front wing. maybe program in 2 position settings on a switch, one for tight maneuvering and one for ground effect!

Derrik
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Old Jul 25, 2010, 05:01 PM
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It definately is more stable, but you can only use it for real Strong ground effect flying.

The PAR engines are a good idea, I think they thought the same thing at Universal Hovercraft. Without the PAR engine, it also wouldn't be amphibic.

Marijn
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