Kerswap 490 (oz8971)

About this Plan

Kerswap 490. Radio control model for RC old timer class A or B glow or ignition. The original free flight Kerswap design was by Gilbert Morris, in 1940.

Quote: "Gil Morris' Old Timer classic has found favor in many SAM events. This version is for all-out competition in the "A" class, using .21s

Typically, modelers who build and fly Old Timers are divided into two camps. The traditionalists insist on replicating the late 30s and early 40s aircraft to the last detail, including ignition powerplants. The new-breed instituted changes, including radio control, scaling (up-sizing or downsizing) and - gasp! - modern glow engines. Both camps have their followers, and a sure-fire way to initiate a lively debate is to put several modelers from each camp into a room with the objective of developing a set of competition rules. When I discussed this article with Bob Hunt, I pointed out that a number of Kerswaps have appeared in the model press, including my original size for 1/2A Texaco (RCMB 11/85) and Bob Aberle's (FM 11/86, CF-736).

The twist on the Kerswap 490 is that it is new-breed all the way. This airplane is radio controlled, scaled up from the original, and structurally designed to handle the power output from the hottest of schneurle-ported glow engines. In short, this one is designed for top level competition and will hold its own in any company.

Interestingly, the Kerswap's designer, Gil Morris, dropped me a note after my 1/2A Texaco model was published. Gil said that the airplane really should have been named the Kerthrash. It seems that Gil was having a problem trimming out his fleet of the little ships and, inevitably, they would pile in. Gil's buddy would yell Kerthrash which sounded to Gil like Kerswap - hence the name which stuck.

SAM Old Timer rules allow scaling (R/C only) with some pretty simple formulas. To be legal for SAM OT R/C, a design must have a minimum of 225 square inches of wing area for each .10 cubic inches of engine displacement. Since my flying buddy, Bob Frazier, promised to provide the engines for this project and he owned two each of the super hot 3.25 and 3.5 K&B front rotor schneurle ported engines, a design starting point was built in. It was determined that 490 square inches of wing area was about right for this project. This would allow some quick engine swapping to make the airplane eligible for either "A" or "B" LER (Limited Engine Run) events and provide a few extra square inches of wing area to aid the effort of trying to build to the minimum weight limit of 10 ounces/square foot.

After weighing all the components (engine, Futaba mini receiver and servos, landing gear components, and other miscellaneous items necessary for radio installation) it was determined that only 14 ounces were available for building and covering the complete airframe.

Fellas, that is a tough assignment! Most of the people that have become interested in OT R/C have come from other segments of the R/C hobby. Your average R/C sport air-plane is kit built with whatever wood comes in the box. With few exceptions R/C kit wood is heavy! You are going to have to haunt your favorite hobby shop and pick through a lot of wood to get the 7-8 pound/cubic foot wood necessary to build this airplane to the mini-mum weight requirement.

If you can get your Kerswap built within a couple of ounces of the minimum weight, you will be rewarded with the hottest flying Old Timer you have ever had the pleasure of flying. That's enough of the soap box and history; it's time to get this beast together..."

Kerswap 490, Flying Models, August 1994.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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