Peyret Alérion
https://en.m.wikipedia.org/wiki/Peyret_Tandem
I have been thinking about this design for a while now, and wanted to get everyone's thoughts on a few questions: note that the 1923 design would meet FAR 103 regs for weight. I am envisioning something along the lines of a Sandlin Goat or Pig, something open air, and able to roll launch at ridge sites, so a monowheel gear with plenty of ground clearance aft with similar construction techniques to Sandlin's designs. Advantages might include being able to design lighter spars and bracing since the spans will be shorter, and some of the particular and peculiar advantages of a tandem layout like deep stall resistance and wider CG range.
Challenges:
As Topaz has mentioned, four wingtips are draggier than two. How effective are wingtip devices at these slow speeds and light wing loadings? (Vs 17-24, Vne 55) I'm amazed by the claimed performance numbers of the Lazair design, could part of this be due to its wingtip arrangement? If nothing significant can be accomplished to reduce the increased induced drag of the layout, I wonder how it compares to the biplane rig with its associated interference drag? In any case, if I'm designing in the spirit of Sandlin's ethos of light, slow, safe at the expense of L/D, perhaps this particular point is not going to be a deal breaker.
Which brings me to my next challenge: downwash, airfoil selection, longitudinal and vertical wing separation, and how all these interact on the original (supposedly successful?) design and on similar projects like the flying flea. The original had severely undercambered airfoils which I'm sure had some interesting Cm and downwash (not to mention limiting spar depth). I've read preliminary text on the flying flea slot effect problem - why didn't Peyret's designs suffer the same issue? Is it the 2x chord longitudinal separation between wings? The identical vertical placement?
Last challenge: Peyret's fuselage design looks like a truss with 5 longerons, perhaps with the nodes sheeted with plywood (need more info.) Despite the fact that he used full span "flaperons" on both wings that deflected simultaneously during a roll command (and opposed each other for pitch), I see some potential for significant fuselage torsion loads, gusts, etc. A goat fuselage would be inadequate. A triangular torsion truss would take it up well, but might be heavy. A large tube would carry it more efficiently, but could be problematic for pilot placement and attach points, not to mention taking it outside the "garage technology" scope that Sandlin purveys.
I appreciate any thoughts on the matter, even if it's "you're crazy. Don't do this."
Also, remember, as long as it meets FAR 103, can safely carry a 230# pilot with Wills Wing Falcon-like performance, it will have succeeded. It doesn't need to approach glass slipper performance.
Austin
https://en.m.wikipedia.org/wiki/Peyret_Tandem
I have been thinking about this design for a while now, and wanted to get everyone's thoughts on a few questions: note that the 1923 design would meet FAR 103 regs for weight. I am envisioning something along the lines of a Sandlin Goat or Pig, something open air, and able to roll launch at ridge sites, so a monowheel gear with plenty of ground clearance aft with similar construction techniques to Sandlin's designs. Advantages might include being able to design lighter spars and bracing since the spans will be shorter, and some of the particular and peculiar advantages of a tandem layout like deep stall resistance and wider CG range.
Challenges:
As Topaz has mentioned, four wingtips are draggier than two. How effective are wingtip devices at these slow speeds and light wing loadings? (Vs 17-24, Vne 55) I'm amazed by the claimed performance numbers of the Lazair design, could part of this be due to its wingtip arrangement? If nothing significant can be accomplished to reduce the increased induced drag of the layout, I wonder how it compares to the biplane rig with its associated interference drag? In any case, if I'm designing in the spirit of Sandlin's ethos of light, slow, safe at the expense of L/D, perhaps this particular point is not going to be a deal breaker.
Which brings me to my next challenge: downwash, airfoil selection, longitudinal and vertical wing separation, and how all these interact on the original (supposedly successful?) design and on similar projects like the flying flea. The original had severely undercambered airfoils which I'm sure had some interesting Cm and downwash (not to mention limiting spar depth). I've read preliminary text on the flying flea slot effect problem - why didn't Peyret's designs suffer the same issue? Is it the 2x chord longitudinal separation between wings? The identical vertical placement?
Last challenge: Peyret's fuselage design looks like a truss with 5 longerons, perhaps with the nodes sheeted with plywood (need more info.) Despite the fact that he used full span "flaperons" on both wings that deflected simultaneously during a roll command (and opposed each other for pitch), I see some potential for significant fuselage torsion loads, gusts, etc. A goat fuselage would be inadequate. A triangular torsion truss would take it up well, but might be heavy. A large tube would carry it more efficiently, but could be problematic for pilot placement and attach points, not to mention taking it outside the "garage technology" scope that Sandlin purveys.
I appreciate any thoughts on the matter, even if it's "you're crazy. Don't do this."
Also, remember, as long as it meets FAR 103, can safely carry a 230# pilot with Wills Wing Falcon-like performance, it will have succeeded. It doesn't need to approach glass slipper performance.
Austin
