Little John (oz12464)
About this Plan
Little John. Radio control sport biplane model.
Quote: "Here's a reduced-size version of Bill Northrop's popular Big John biplane, designed for 40-to 48-size four stroke engines. Little John, by Alex McCleod.
Having built and flown a Lil Beau Bipe (oz1601), a Wild Child (oz1357), a Duster (oz1943), a Galloping John (oz2882) - yes, with all of that banging and flopping at the tail - and even a friend's Big John (oz2364), I was sold on Bill Northrop's all-size biplane design. There isn't, however, a size to fit the 40-48 four-stroke engines. Here then is my presentation of the Little John Bipe (with apologies to WC Northrop).
It flew quite gently with an OS 40 four-stroke and was a real winner, a pussy cat. I thought it had a lot of aerobatic potential, and I was right. With an OS 48 Surpass, the vertical maneuvers are a joy. Not everyone will want a fully aerobatic airplane, but on low rate at the transmitter and two-thirds throttle, its a real Sunday flyer again. When the power is cut back to one third, it will just hang in the air with a little up elevator and almost thermal. On idle it can be landed at a very low speed. This is due to a light structure and generous wing area. At five pounds, my LJ came out at a 16 oz/sq ft wing loading. A 48-inch wing span makes it a one-piece airplane for transporting in small cars. Perhaps you may even build it lighter by using heat shrink covering films. I used Sig Coverall and butyrate dope for a more permanent finish. The bottom line, however, is keep it light.
The semi-symmetrical airfoil, used on the Little John is very similar to its big brothers and makes inverted maneuvers quite comfortable. The large rudder makes knife edging quite easy with a little down elevator. Slow rolls and eight-point rolls are quite axial even at low speed. The ailerons are extremely effective right up to the stall which is quite gentle. With up elevator and careful application of power, it will even hang mo-tionless in a strong breeze. It is really a fun airplane.
CONSTRUCTION: I like to take an airplane with me when I holiday in Vermont, therefore, I usually build them so they can be completely taken apart and transported in my model box, which is 47 inches long on the inside. For that reason I built the wings 47 inches long instead of the 48 shown on the plan.
It seems to be the style now to say that I'm not going to go into detail about how to glue each piece to the next. I won't bore you with a piece-by-piece description then. There are, however, a number of special paints to be mentioned. The first thing I usually do is make up a kit by cutting out all the parts and collecting all the necessary hardware and accessories.
Start with the wings and cut out the 34 balsa ribs from 3/32-inch medium sheet. An easy way to do this is to make a cutting tem-plate from .035 soft aluminum siding with jagged holes punched near each end to hold it on the balsa sheet. If you don't have any of this aluminum, find a construction site where this is being used and beg or buy as much of the scrap as you can. All of the ribs are the same size but where differences are needed. The basic rib can be doctored to suit.
The 1/4 x 1/8 spruce spars top and bottom of each wing are plenty strong enough, with vertical 1/16 sheet webbing for rigidity (Don't build the wing without it!). The 1/8 sheet sub leading edge and 1/4 sheet leading edge, make it simple and strong. A smooth and consistently shaped airfoil is assured with the 1/16 sheet leading edge and trailing edge, joined by 1/16 x 1/4 cap strips on the ribs. This type of construc-tion is one of the lightest and strongest t know.
Both top and bottom wings are built in three pieces and assembled with dihedral braces giving 1-1/2 inches of dihedral at each tip. Don't forget the 1/4 ply blocks in the top center section for the cabin struts and balsa blocks in the lower center section for the wing hold on bolts. The 1/8 ply blocks in top and bottom wings for the out-board N struts are glued in place so the right angled brackets can be bolted down..."
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