Nacelle protection? Or, do a Boeing? - RC Groups
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May 14, 2001, 10:39 AM
jrb
jrb
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Nacelle protection? Or, do a Boeing?


What's the best way to keep the fan units protected during landing when mounted under the wing?

The bottom of my fans (twin) and fuselage are coincedent; and the fans popped off as planned (if needed) on 1st grass feild landing.

Looking for good ideas or I might just do it like Boeing and mount them on the top of the wing.

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May 14, 2001, 12:55 PM
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The reason for the fan under the wing may be to keep the airfoil clean also to keep the weight low ? I used to land my low fan foamy in tall grass then the nacelles never got hurt
May 14, 2001, 04:00 PM
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Well if you did not want to put landing gear you could (this is going to be stupid) put a retracable skid-like structure on it, or just something to absorb the initial impact. Maybe even just a single retactable wheel in the center to take off pressure from the nacelles.
Andrew
May 15, 2001, 07:24 AM
Registered User
hi
the nacelles are below the wing cause the air above the airfoil flows faster in order to decrease the pressure( and by that creating lift).it is better to mess up the lower side of the airfoil than the upper, which must be kept smooth for better perfrmances (other than keeping it all clean for less drag).
about the skid, just install one on the bottom of the fuse and make sure you land with wings horizontal so the skid takes the hit,as seggested. don't even bother about retracting, simply give an aerodynemical shape (gradually growing and rounded corners).

hope it helps
Avi E.
May 15, 2001, 08:39 AM
bjh
bjh
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An interesting tidbit I found out a while back about all the full scale jets with wing mounted engines (B757s,DC-10s,B747s,etc) - They are actually designed so that the engines actually pivot around the leading edge of the wing and depart the aircraft over the upper wing surface in the event of a "gear-up" landing or other emergency situation. Not sure how well that will work for an RC jet, but it'd be interesting!!
May 15, 2001, 08:45 AM
jrb
jrb
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Thanks for the ideas; did a Boeing though.

By Boeing, I mean with nacelles mounted on the top of the wing rather than bottom (B747). Boeing (and Russians copied) did a fand STOL transport in the 70s with the nacelles mounted on top of the wing and out ahead of the leading edge. Lift was increased by having fan air blown over the top of the wing.

Now nacelles won't fall-off on landing and I can use the launch box/pedal w/bungee.
May 15, 2001, 10:58 AM
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Sabrejock's Avatar
'Way back, I contemplated installing a fixed gear leg close beside and inboard of the nacelle, and using a Lucite (Perspex) wheel which would just clear the nacelle. I never got a "round tuit" but it could be considered. Tex.
May 15, 2001, 11:01 AM
Registered User
Greetings -

The underwing nacelles also serve as anti-flutter weights which allows for a lot lighter wing structure. Just look at a B-47 (where the idea really came to fruition) and from there on to the B-52 and Dash 80 (aka 707, KC-135, 720, etc.) Also minimizes airflow disturance to the wing (it "flies" in clean air) although clearance and nacelle length are important factors.

Fly Fast! Mark
May 15, 2001, 06:13 PM
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gkamysz's Avatar
The real reason for under wing installations is that they are so much easier to service.

Greg
May 15, 2001, 06:37 PM
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It would make it easier to suck Maintenance Crew up off the tarmac