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| Finished Allegro Lite RC Sailplane |
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| Allegro in Flight |
With the all the plans and instructions downloaded from the Charles Rivers website I started the construction of the Allegro Lite on a glass surface using bags of bird shot for weight as recommended. Building the wing was an overwhelming task for me, it is a combination of balsa and composite materials. Spar construction consists of end grain balsa sandwiched between carbon fiber strips. This is wrapped with Kevlar tow (loose fibers) and then painted with a slow curing epoxy. The design objective for this sailplane was for it to be able to withstand any flying load including full-pedal winch launches. A friend of mine did manage to break the tailboom on a particularly brutal launch with his Allegro Lite.
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| Wing Spar and Tip |
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| Another View of Spar After Sheeting |
Obtaining the special components needed for this project was somewhat easier in that I obtained a partial kit that had those composite components and laser-cut ribs. Building the wing was such a task that at some point I felt like if I finished this plane and it crashed it I would be devastated. It sat for years at about 90% complete and then I started slowly working on it again last winter. Just within the last couple of weeks have I started flying the glider. It flies very well but somewhat faster than I had anticipated. Still nervous flying my pride and joy I have only made thermal flights of no more than 5 minutes by making big circles over the field.
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| Hatch Held With Magnets |
If more nose weight could be crammed in the tiny nose pod it would be good to try because the CG is slightly behind the recommended spot and it seems to be close to tip-stalling occasionally. I used powerful tiny magnets to hold on the nose hatch this has worked very well.
What a feeling of accomplishment I have from building this model airplane.
Bill Kuhl
http://www.ideas-inspire.com
Additional Resources
Charles River RC Article and Plans for Allegro Lite
Dr. Mark Drela MIT
XFOIL Airfoil Program
Daedalus Human-powered Record Setting Airplane
Download Plans for Rubber Power Free Flight Corsair Designed by Mark Drela
Human Powered Speed Record Set on Water - Decavitator
Some years back, I had a chance to fly Mark's Allegro Lite for a few minutes. The stall was a little sharper than on some models, but totally manageable, unlike the old Prodigy from several decades ago. Handling and performance were excellent. That seems to be true for all of the Drela designs I've been fortunate enough to try. I've seen Mark winch launch his Allegro Lite. Full pedal. The speed just doesn't look right; the visual equivalent of playing a 33 rpm LP on 78. I think the AL has inspired a bunch of F3-RES models, some of which should be much easier to build, but I doubt any are strong enough for hard winch launches.
ReplyDeleteI hope by now that you've flown the Allegro Lite many times.
BTW, I've also been lucky enough to see Decavitator, as in your last link, on the water. Once it was up on the foils, that much speed didn't look right, either.
Outerzone has 4 Drela plans, though I don't know how much of the Apogee Sport is his. I have flown a couple of the original Apogees, back when we still threw overhand. Very fun.
https://outerzone.co.uk/search/results.asp?keyword=drela
I haven't seen the 3 rubber powered models.
Lincoln Thank you for your comments. I have a bunch of flights on the Allegro Lite over the years. I find too you want to keep the speed up or it can tip stall. The stab bracket broke this summer and I need to re-glue, epoxy appears to get a little fragile over years. The wing is still super solid. I built a Monarch Ascension which is lighter.
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