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Help! To Hoerner or Not to Hoerner?

#1
That is the question. Though looking at most Flite Test foamboard aircraft wing designs where the underside and wing spar do not reach the tip, is this not pretty much a Hoerner "Style" wingtip already?
Case in point is the wings on the FT Guinea Pig. The front edge is curved with a sharp trailing edge, and thin because the bottom with spar ends several inches short of the wingtip. (A SB-6 and Parker version of Hoerner wingtip). Is this the idea when these wings are designed?
My only... problem with this wing is the open holes exposing the spar and internals. FOD and moisture are not friends of such light aircraft, and/or foamboard. But if I enclose the wingtips with shed paper during the build from other areas such as the nose, do I run the risk of fouling the current (if any) positive effects of this design?
I do plan to test this on an stock Guinea Pig I own, and on a modification still in the design phase to be known as "Mama Guinea". Mama Guinea is planned to have a 7.13" X 7.13" cross section fuselage. A width increase of 1.67". Thus I have planned to lengthen the wings to 60" from 58" through the center to keep the nacelles and spar end to wingtip spacing equal to the original. This will also increase the wing area from 522 inches squared, to 540 inches squared. By thinly gluing external foamboard paper from the spar end bottom plate out to the curved external outer edge of the wing, this in effect will seal the wing, and formally create a Parker version Hoerner wingtip. (Also including NAV and Anti-Collision lights).
I would appreciate any and all comments or questions concerning this. I will include a design drawing of my modification upon request.
 
#2
That is the question. Though looking at most Flite Test foamboard aircraft wing designs where the underside and wing spar do not reach the tip, is this not pretty much a Hoerner "Style" wingtip already?
Case in point is the wings on the FT Guinea Pig. The front edge is curved with a sharp trailing edge, and thin because the bottom with spar ends several inches short of the wingtip. (A SB-6 and Parker version of Hoerner wingtip). Is this the idea when these wings are designed?
My only... problem with this wing is the open holes exposing the spar and internals. FOD and moisture are not friends of such light aircraft, and/or foamboard. But if I enclose the wingtips with shed paper during the build from other areas such as the nose, do I run the risk of fouling the current (if any) positive effects of this design?
I do plan to test this on an stock Guinea Pig I own, and on a modification still in the design phase to be known as "Mama Guinea". Mama Guinea is planned to have a 7.13" X 7.13" cross section fuselage. A width increase of 1.67". Thus I have planned to lengthen the wings to 60" from 58" through the center to keep the nacelles and spar end to wingtip spacing equal to the original. This will also increase the wing area from 522 inches squared, to 540 inches squared. By thinly gluing external foamboard paper from the spar end bottom plate out to the curved external outer edge of the wing, this in effect will seal the wing, and formally create a Parker version Hoerner wingtip. (Also including NAV and Anti-Collision lights).
I would appreciate any and all comments or questions concerning this. I will include a design drawing of my modification upon request.
IIRC the goal of the undercambered FT wingtips is similar to washout: presumably, the undercambered outer foil stalls at a higher angle of attack than the rest of the wing, reducing the tendency to drop a wing in a stall and affording one better roll control near and in one. I'm not sure what effects modifying the wingtip in this way would have, it's certainly an interesting experiment.
 

Piotrsko

Master member
#3
The advantage of a hoerner tip is the high pressure is allowed to wander from the higher pressure bottom to the end in a controlled way thus avoiding making the vortices bigger. AFAIK, there's no noticeable effect at model scale and size because we operate in the transitional area of the Reynolds graph.

If you want to close the end of the flatbottom for aesthetic reasons, go ahead. Make a rib piece and glue it on, or tape is always a favourite