Ohmlette (oz10427)


Ohmlette - plan thumbnail image

About this Plan

Ohmlette. Radio contol model for electric power with Mabuchi RS 300 motor. Uses all-sheet construction and a Jedelsky style wing.

Quote: "Ohmlette, by Gordon Inwood.

Hands up all those modellers who have had a sneaking suspicion that electric flight could be for them. Good. Now, hands up all those who thought it was too expensive, too technical or needed specialist, sophisticated equipment - mmmm - nearly everybody. Well, here's a design that may just change your minds! Ohmlette's the name, cheap low tech flying is the game. If you get your 540s confused with your 380s and couldn't tell one end of an ammeter from the other, now's your chance to begin picking up the basics with what must be the cheapest airborne pack, ie nicads and motor possible (short pause whilst waiting for a pile of contradictory letters to drop through the letter box).

If, on the other hand, you confess to being a seasoned old timer - (salt and pepper?) you might like to build one just to prove to yourself how useful small electric models can be. Ohmlette slips easily under a car seat or into the boot, trips out with the kids can almost be looked forward to! Do remember though, whilst small and quiet, the usual commonsense rules of safety and consideration still apply.

Now, before we go any further, let's get a few facts straight:

1. 380 sized motors do produce a useful amount of power, provided they're propped correctly, in this case a Cox 6 x 3 and fed a diet of seven 600ma Sanyo pencells.
2. Jedelsky wing construction is a viable, useful type of wing construction - if you can't take my word for it, ring Robbe who currently (sic) market a thermal/slope soarer, with this type of wing.
3. This model will fly, not stooge, for about four minutes minimum on this cell and motor combination.

I hope these points help dispel any doubts amongst those of you thinking of building Ohmlette.

Construction Let's start with the wing. Anybody who's not had the pleasure of building a Jedelsky wing is in for a big surprise, Fast? Easy? You betcha! First cut out the dozen ribs - being of all straight lines this shouldn't take long. Note the ribs are longer than the chord of the wing; this makes them easier to pin down. The choice of timber for the two pieces of sheet which make up the wing is, though not critical, quite important. The wood needs to be firm and straight grained, neither stringy nor too soft.

Once cut to shape, the 3/16 in leading edge sheet needs the sanding block passed along its rear edge, bevelling it so it fits neatly against the rear, trailing edge sheet. Pin the ribs over the protected plan, not forgetting to angle the root rib to allow for dihedral. Using cyano, glue the rear sheet into place, check for fit and then, again using cyano, glue the We sheet into place. Repeat for the second panel, ensuring (as we always do...) that a pair of wings result, not two left hand panels.

After lifting the second panel from the board, sand the root ribs to a neat fit and join the two panels with five minute epoxy, propping up one tip to provide dihedral. When the epoxy has properly set, sand the finished wing to the profile shown on the plan, trim the ribs to their finished lengths and add the ply wing seat. The job is completed with a 2in strip of glassfbre tape applied around the centre join. Time taken so far, about 2 hours..."

Quote: "Ohmlette. The pre LiPo/Outrunner electric era was an interesting time when many a model found itself named using a cheesy pun related to electricity. Gordon Inwood's 1992 Ohmlette is a prime example but also an excellent and easy to build small model that would work very well with the newer technologies. Many magazine plans in the pre CAD era were real works of art and I have the greatest respect for the draftsmen responsible. Once in a while though you had the impression that the designs had only come in the night before close of press and things had to be done rather too quickly. Sadly Ohmlette is one of these and there are some anomalies on the plan: Despite appearances the distorted formers (particularly F2) at the right of the plan are not caused by bad scanning but were like that on the original, also the angle of F1 (labeled as F4 to the right) suggests down-thrust, yet the bearers are level. There may be other issues..."

Direct submission to Outerzone.

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