Building A 1/3 Scale Swift Flying Wing by Vern Hunt
Poor unsuspecting Vern sent me a photo of his Swift. I thought that it was a fantastic model and persuaded him to send enough details about it to make a page. I will add it to the long list of my projects...
This flying wing came about after admiring the Swift design and being interested in ultralight and full size soaring. I couldnít afford one, so I decided to build one myself.
After many months of research on the Swift airfoil, I finally drew up what I thought would work. This airfoil is for a full scale wing, so I decided to build a 1/3 scale proof of concept model. Rather than cut foam cores for this wing I wanted to use built up construction to further gain experience toward the full size glider. So, this wing is all wood, spruce, balsa and fabric covered.
It is fairly easy to construct if you set up a building board accurately and big enough. There is 8 degree of twist in this wing, therefore the building board must reflect that washout. The spars are spruce and had to be spliced to make up the required lengths. NOTE :- The sweep dimension is 24.5 inches. (This is measured at the last straight section of the leading edge) The CG is 15inches back from the leading edge at the center. The top and bottom main spars are 1/4" square. The rear spars are 1/4" x 1/8" laid flat. All the ribs are 1/8" balsa. The spar cutouts are done as the ribs are placed in their locations. After the bottom spars are pinned in their proper location, the ribs are placed and pinned. Then the top spars and the leading edge. (1/4" balsa). After youíre satisfied with the line-up of everything, glue the ribs to the spars (I used thick CA then zip kicker). The elevons are built in place, then cut out after final sheeting and sanding. The cross-through spar is 1/4" aircraft plywood. A box is built around this spar for both halves of the wing, then laid out and cut into each wing half from the bottom. My root rib outer caps are 1/4" ply glued and glassed to each center section. All external sheeting is 1/16" balsa. Front and rear spar webbing is also 1/16" balsa. The tip rudders are foam core with lightening holes cut into them, of course fabric covered. You can use any hinges you like, but for ease I used tape. The servoís are standard size, outboard location. The wing is Sig Coverall fabric covered and two coats of Nitrate dope.
Mine weighs 8 lbs ready to fly. Iíve only flown it on the slope, but Iím sure aero-tow would be just fine. Flying is a joy, very docile and smooth. Almost flies itself. Very controllable right down to walking speed. It doesnít seem to stall at all. Iíve landed down wind into the hill without problems. Even on marginal days I can bring it back to my launch spot and not worry. When thermals are present itís just a blast, because it turns on a dime and you can work even the weakest of lift.
Vern has been building wings for a while. Here are some of his previous models!
#1. 120" Wingspan This wing is a development of the successful 100" electric motor glider. Utilizing the SD 7012 airfoil(modified), I molded a glass center section to house the radio equipment. The panels connect to the center section, utilizing a flat carbon spar. This wing is both a slope and flat-land thermal soarer. It launches straight and true every time on the winch. My wings are sheeted with 1/32 ply over blue foam cores. I then cut lightening holes to save weight and covered with sig coverall. It's absolutely gorgeous in the air.
#2 100" Wingspan This wing was part of the early days using Eppler airfoils. This wing worked well, but it wasn't as soarable as I had hoped. It is steady on the winch and I must have launched it 500 times. Wings are beautiful in the sky and I've stuck to them for that reason.
#3 100" Electric Motor Glider This model was an experiment I tried utilizing the SD 7012 Mod. airfoil. I molded a center section to house the radio and motor/battery. I turned out very light so I winch launched it to see if it would fly before I put the motor in it. Well, it not only flew, but became my most soarable wing yet! I never put a motor in it.
#4 80" Wingspan This experimental wing was designed with the MH 32 airfoil. It is a slope glider only, built for speed and aerobatics. Lots of fun to fly, very stable. It turned out heavy, but surprisingly it will thermal quite well.
#5 72" Wingspan (UFORIA) This was one of my first successful wings. I followed all the rules of sweep/twist, airfoil, etc. and it flew great. Winch/slope were fun and I built several different sizes and variations which I still fly today.
#6 70" Wingspan Part of my UFORIA series, this wing was a try at making a very light small thermal glider...it worked! Notice the Horten influence. I've always loved the Horten wing designs.
#7 45" HLG This is my newest wing. I always liked the RG14 1.4/7 airfoil, so I thought I'd try it on a flying wing. Micro radio equiped, it came out at 9 oz. What fun! I take it across the street to a small park and it's been a blast. Just a joy to fly. Indicates small thermals with a wag and up it goes in tight circles. I carry it to work and fly on my lunch hour. Cheap and fast to build. I'm using the HITEC single stick radio with elevon mix. 2 HS 50 Feather servo's in the wing.