Jimp (oz2603)

About this Plan

Jimp. Free flight gas model, from 1950 model plans annual.

Quote: "Jimp, by CA Allen. Plans and instructions for building the F/F winner of the 1949 Northern Heights Gala.

THIS simple pylon model was especially designed to suit the ED Comp Special, but any similar (2-3.5 cc) diesel may be fitted, such as the ED 3-46 or Amco 3.5. Glo-plug motors of the Yulon 30 and ETA 29 types should also be suitable. Still air duration on a 10-second motor run is consistently over 2 minutes. Best flight to date has been one of 5 minutes OOS. At the 1949 Northern Heights Gala Day, this design won with a 100 seconds plus on a 5-sec run. Second place was also gained at the North Hants Rally. The slightest thermal is enough to keep the Jimp floating around and for this reason a dethermaliser is advisable. A fuse-operated parachute of about 14 in dia is about right.

Construction of the model is particularly simple and the airframe weight works out very light. Only a few evenings are required for building and field repairs are aided by the straightforward structure. The square-tipped flying surfaces seem to be just as efficient as the rounded type - and have of course the advantage of being easier to build.

Scale up the drawings to full size or write off for the 40 in x 30 in plan to the publishers. Full-size ribs, formers and other parts are provided on the next page. Pin-prick or trace these patterns on to the appropriate size sheet.

FUSELAGE: Make up the pylon from 1/4 in sheet (P1-P4), remove from the plan when dry, then cover both sides with medium 1/16 sheet. The fuselage side frames are built flat on the plan in the usual way - one on top of the other. When quite dry, lift the sides up from the building board and separate with a razor blade. Now add the hardwood bearers and join the two frames by means of the formers (F1-F6). Note that the F1 and F2 formers are sandwiched together. Pull in the frames at the tail end, cement, and add the upper and lower spacers. The fuselage is 1 in wide at the tailplane leading edge position.

Bend the single-leg undercarriage from a piece of 14 gauge wire and bind securely to the bearers. Add the 1 in x 1/8 in tailplane saddle and install a diesel type timer behind former F4. Fill in the top of the fuselage back to F6 with fairly soft 1/8 sheet to provide a large ccmenting area for the underneath of the pylon. Cement the pylon in position, noting how the tongue on P1 butts up against F2. Fair in the fuselagelpylon joint with plastic wood

WING: Begin this component by building up the main spar flat on the plan - using splice joints. Use pins to hold the spar strip to the plan and add the W2 and W4 braces on one side. When dry, lift up and add the braces to the other side.

Build each of the four panels flat on the appropriate sections of the wing drawing. Start with the inboard left panel and pin the spar in position. Next pin the unshaped leading and trailing edges to the plan, followed by the ribs. Check carefully that the ribs are vertical and notch all except the ones at the dihedral breaks into the trailing edge. The rear upper spar is next added. Note that the W5 and W7 ribs are tilted inwards slightly. When the panel is dry, remove the pins and pivot on W7 until the tip spar is flat on the tip panel. Tip construction is similar except that no upper (rear) spar is featured in this case.

The right-hand panels are built in a similar manner and when completed the tips, leading and trailing edges are all shaped to the indicated sections.

TAILPLANE: First pin the leading and trailing edges flat on the plan. Then attach the ribs and follow with the 1/4 in square upper spar. Cap strip the upper profile of the centre rib with a piece of 1/32 sheet (3/4 in wide) to protect the covering from the tailplane fixing bands. Make the fin flat on the plan and add to the tailplane after both have been covered and doped.

COVERING: The fuselage is covered with double weight rag tissue. Cover the wings with eight separate pieces of coloured tissue and the tailplane with two. Give the fuselage three coats of clear dope and the flying surfaces two coats. Finish off by giving the complete model a coat of banana oil. Red or orange tissue is recommended for the flying surfaces as it shows up well at a distance..."

Direct submission to Outerzone.

Note colour photo of Jimp model built by Arthur Fox [main pic] is from R/C Model Flyer, Nov 2000, thanks to RFJ.

Supplementary file notes

Planfile includes article (incomplete).

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