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SD-1: Kinda neat

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Vigilant1

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The US distributor for the SD-1 aircraft brought his project to our EAA chapter meeting this week, I really enjoyed the presentation he gave and the chance to paw around the airplane. From the picture's I'd seen (lots of swoopy shapes), I'd assumed this little single-place plane was primarily composite, but that's not quite right, the primary structure is wood. Simple spruce longerons glued up flat on a table and thin ply make up the fuselage, the wings are very thin plywood over foam ribs (a few of the ribs have CF caps and facings to transfer loads across the skins and to the spars, but most are just foam to provide local support to the skin). I would not have liked to cut all the custom gussets/blocking for all the fuselage joints (wouldn't it be only slightly heavier and much faster to just press in some epoxy/flox into the open spaces after the structural members are in place? The pieces are glued to the ply skins anyway, like a huge surface gusset).

Seems like a very cheap plane to fly and own. The one I saw had a 50HP Hirth with a PSRU, but others are being flown successfully with small industrial engines, etc. They probably burn 2 GPH. Wings are easily removable (a two person job with the plane I saw, but it would be very easy to design a fixture to allow it to be done solo). Each wing half weighs less than 30 lbs. It's small: 20' wingspan, about 14' long, and an empty weight of 300 lbs (MTOW: 580 lbs). Cruises at 118 MPH (75% power from the 50 HP Hirth).

It's clever how the kit-supplied composite parts (cowling, cockpit fairing, tail fairing, wingtips) do a good job of disguising/changing the look of the very boxy and straightforward fuselage. The pricing on the kits/parts was a bit confusing, but a 51% airframe kit was less than $9K, the Hirth F23 (50 HP) with engine mount, PSRU and prop is $7900. I'd guess you could buy everything needed to fly for less than $20K, and be in the air for much, much less than that if you are willing to do more finding/cutting of your own wood, use a B&S, Kohler, or Robin engine, etc.

They have a two seater (SD-2) coming out soon. Similar concept, takes 65-120 HP, maybe a little faster cruise speed. The wing has a 29' span and an area of 98 sq ft, the MTOW is 1050 to 1222 lbs, so I'd think it might be fine with cheap VW power if flown somewhere around 1100 lbs (which would still give a useful load of about 500 lbs).

I have no connection with the company selling these kits. I just thought it was an interesting design along the lines of the PIK-26, etc.

Anyway, I suppose I'm not adding much to what is already published about this design. It's a Czech design, and I think there are more of them flying in Europe than in the US. But it was cool to see one in the flesh, and good to see relatively simple, lightweight plane designs still coming to market. ss9.jpg ss12.jpg pf2017web.jpg
 
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