Mid Jet 2 (oz12834)
About this Plan
Mid Jet 2. Radio control slope soarer model.
Direct submission to Outerzone.
Note there is a great build thread of the Mid-Jet on RCGroups by WLJayne (using foam wings), see https://www.rcgroups.com/forums/showthread.php?1457504-Mid-Jet-Evo-build-thread with lots more info and some great pictures - sampled here as the main model pic.
Update 27/02/2021: Added complete article, thanks to RFJ.
Quote: "Mid Jet, by Les Rudd. Snappy mini slope soarer, for 2-function R/C. 38 in of fun.
PERHAPS the greatest appeal of this model is its size for, with a little bit of extra work, once 'Mid-Jet' is finished, a simple box a mere 21 x 8-1/2 x 4 in can be made to accommodate the model. This ensures that almost no-one will notice that you have taken a soarer with you on holiday until you innocently park the car near a convenient ridge and slide the box out from underneath the car seat! Of course, you have to be fairly cunning when it comes to providing a good reason for a search through local shops for an Ordnance Survey map of the holiday area. A convenient sized model we can provide, the excuses are up to you.
Using the wing section shown on the plan, the model is suitable for a strong blow, alternatively for light breezes a flat bottom section could be used. Unfortunately, both wings demand a bigger box; super cunning is required then. Mid-Jet II breaks down into 3 pieces for transport, but once assembled the jet-like, tailless design is a fully massive 36 in. span and of a style that cries out for a scalish colour scheme. Two function standard size equipment is fine, a simple mechanical mixer copes with elevon controls although a transmitter electronic mixer can of course be used if you possess an all singing and dancing R/C system.
Body: (is it big enough to call fuselage?) The servo support should be made first as with the servos fitted the linkage can be made up and operation checked for smoothness (see sketch on plan). If using smaller servos than shown, adjust the support cut-outs to suit but keep them to the rear as weight distribution is opposite of conventional, that is, make the nose light. The rear servo sliders being made of the same ply as the support need to be sanded slightly thinner. Rubbing the ends of the slides with pencil leads helps. Note that on the plan and side views Fleet servos are shown, with the elevator servo (front) 'hooked up' to the aileron servo (rear) making use of one of the top cover front fixing screws, whereas in the sketch, other servos are shown with the linkage between the two going to the arm drive spindle.
First choice of servo sense must obviously be for the aileron function, elevator can come off either side. Perhaps you might feel that the rear servo slide movement does not seem to be logical, moving rearwards and when driving and vice versa. Don't worry, the plane doesn't seem to realize this! When assembling the body sides to the servo support they will be self-aligning if the two tube holes are accurately positioned. This also applies to the wing retaining slots to ensure equal incidence on both wings. The hatch is cut free after shaping the body, the rear end being held down by the angled joint in the fin and at the front by a suitable catch. The 1/16 ply rear-end plate is not really required although it helps as a guide in shaping the corners equally and as a foundation for the dummy jet tube to be glued onto.
Wings: By careful planning, parts for the top and bottom covering can be cut from 3 sheets of 4 in wide 1/16 sheet balsa (see sketch). Note the top sheeting needs to be longer than the bottom because of the angled tip rib, and grain direction for the triangular pieces is parallel to the join line. The 1/32 ply root rib can be used as a template for all ribs (except tip) by marking the cambered edge as shown on plan but remember to retain the leading edge angle to the bottom of rib. After glueing leading edge and ribs to the bottom sheeting the sanding to receive the sheeting is made easier and more accurate by using a sanding block at least 9 in long. Prior to fixing the top sheeting, pack up the leading edge at the four places and by the amount shown on the plan. This gives the required washout. I find it best to use contact adhesive for the top of the intermediate ribs but PVA at leading trailing edges root, and tip ribs (makes for easier sanding).
However, you hinge the elevons try and make them flop under their own weight to save any extra load on the Ni-Cad. I used the figure of eight thread method from single channel days but instead of spreading them herring-bone fashion keep them in one place. A spot of glue on top and bottom allowed to harden before covering will reinforce the area to take the stitches. You might argue why bother with plug on wings? Well there are two reasons. One, to get as much lift area from 36 in. wood as possible and two, to enable different wings to be assessed e.g. alternative planform or section. The second is perhaps something you would like to try for yourself.
General: Obviously you will use your favoured finishing method, mine was iron on film with a USAF theme. Glider ready to fly weight was 14 oz. Initial balancing can be carried out hanging the plane by thread looped around the wing joining rod.
Flying: Nothing much to worry about here (or that's what I found). Mid-Jet II is at it's best when flying fast but when scratching and flying slowly in marginal conditions go easy on control movements. Also at slow speeds if elevator response is somewhat lacking, it indicates a too forward balance point. Even if it means a little ballast in the rear (hidden in the jet tube) you'll find it will stay up better in those light winds. Finally, I would be only too pleased to hear from anyone with their experiences in building and flying this design, be they good or bad!"
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