Miss Martha (oz9991)
About this Plan
Miss Martha. Radio control fun-fly sport model for .40 - .50 power.
Note this is a modern re-drawn plan.
Quote: "You don't have anything on the 'Miss Martha' R/C fun fly model from the 1980s on Outerzone. I created these photos [model photo & more pics 003, 004] & this PDF from sources on the internet when I couldn't find copies of the kit plans. Roughly, it has a 47 inch wing span, uses a two cycle .40-50 size motor & needs a four channel radio. I don't know who designed the Miss Martha or if it was ever kitted. I saw one fly many years ago, I can remember it being really fast for the size motor it used, I think it was a TT .36? & it was really aerobatic. Tight snap rolls, one after the other."
Direct submission to Outerzone.
Update 02/06/2021: Added kit review from Flying Models, March 1992, thanks to RFJ.
Quote: "An FM Product Review: Model Engineering's Miss Martha, by Steve Kulicki.
Dedicated fun-fly airplanes have spawned their own class of model. This one offers robust construction and a wide flight performance envelope.
I was asked to review a plane called Miss Martha about three weeks after our club sponsored a well-attended fun fly contest. I had no plane to fly at this event so I was a good club member and helped time, measure, and pick up parts of planes that hit the poles that held the limbo stick. Come next year and I'll be able to find out first hand how those stationary poles are able to swat planes!
Miss Martha is a Model Engineering kit (5540-105 Atlantic Springs Rd., Raleigh, NC 27604; 919-954-7222) that was originally designed by Robert Richards. After opening the box you realize that everything you need to frame this plane is included. All you need to bring to the workbench is an engine (.25-.40), wheels, fuel tank, glue, hinges, and your favorite covering. This kit is so complete that in addition to all hardware, bolts and screws, even a 10-32 tap for the wing bolts is included.
I usually begin building a kit by looking over the plans and reading the instruction booklet thoroughly. It's imperative that you read the 16-page instruction booklet and become familiar with the discrepancies that exist between the plans and the instruction manual. The material and procedural changes are clearly indicated with bold face type. Therefore, the instruction manual is your bible as you begin construction.
Wing. Construction of the familiar D-tube wing is unique. The wing is built as a single, full span assembly. Two pairs of 1/4 x 1/4 x 36 balsa are bevel cut and glued to form the top and bottom main spars. One of the joined spars is glued to the upper edge of the rear plywood dowel support so that the upper edge of the plate and the spar are aligned and the plate centers over the spar glue joint. The lower main spar is aligned with the lower edge of the dowel support plate in the same manner.
Wing ribs are die-cut and easily pop out of their 3/32-inch balsa sheets. The center ribs and wing tips are die-cut from 1/8-inch balsa. The 1/26-inch balsa shear webs are factory cut and come stacked together. Hold the entire stack and lightly sand all edges until they match perfectly.
Each center rib slides between the spars and up against the dowel support plate. Square these ribs with the support plate and zap all joints. The remaining ribs are spaced evenly by the shear webs that are glued between the main spars. Keep the bottom spar against your building board and place a long straight edge against the upper spar as each rib and web are glued in place. There is no need to pin everything down since this method keeps the spars straight and parallel as they evolve into a rigid structure. Trim off the excess spar material outboard of the tip ribs. Keep all scrap pieces while building this plane. All scrap will be recycled for future use.
Butt glue two 36-inch balsa trailing edge sheets and sand both sides. Glue two pieces of tapered trailing edge stock to the back edge of these sheets. Pin this trailing edge assembly to your building board. Lay the wing structure on top so that it's centered on this assembly. Shim the wing structure under the lower main spar with some scrap 1/4-inch square main spar material.
Ribs are kept parallel with a scrap piece of shear web balsa as they are glued to the trailing edge assembly. The 1/8-inch balsa sub rib is glued in at this time. This piece is intended as an aileron servo mount support. It will hold the 1/4 x 1/4 x 2-3/4 inch hardwood servo rail. Make sure your servo will fit before you glue in the sub rib. The upper trailing edge sheeting is glued in place and trimmed off. The excess sheeting will be re-cycled into the center section sheeting. Glue in the hardwood front spars.
The leading edge sheeting is joined and sanded just as the trailing edge sheeting was prepared. Use a straight edge to trim each sheet to a width of 21/2 inches. Glue in place by first adhering it to the main spar and then working it over the ribs. Remove the wing from the building board and glue on the bottom edge sheeting. Glue the beveled leading edge pieces in place. Glue balsa tip ribs in place and sand the leading edge to shape. The upper and lower center section sheeting is made from recycled leading and trailing edge scrap. Cut a small opening in the lower center section sheeting to accept your aileron servo. Cap strip all remaining ribs. Strip aileron stock is cut to length with the scrap pieces used for both the center of the wing and at each wing tip. You now have a straight, strong, warp free wing.
Fuselage. Begin the basic box fuselage construction by drawing a center line on all four bulkheads. All appropriate holes are drilled in the firewall and the plywood landing gear plate. Bulkhead F-Z is centered on and perpendicular to the right lite ply fuselage side. Triangle stock is glued in between each bulkhead and runs the length of the bottom of the fuse. The top triangle stock extends from the rear of the wing saddle to the end of the fuse..."
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User commentsWish I had photos but back in the '80s our club (Gloucester Area Model Association) GAMA had a ball with Martha's as a club build!!!... Mine was modified to a T tail and shortened the nose 3/4" for a 4stroke .40... such a sweet flying plane!! ...as a trainer a .20 would fly it... 45 2stroke with a pipe and it would accelerate vertically!!!
BillV - 21/04/2018
I have not been able to find a photo with the rudder shape shown on the plan. What is correct? See pict. on plan details.
Karsten - 23/04/2018
I love my Miss Martha, built sometime in the early eighties from the plans before the kit became available. Lots of kit-built models appeared at our field, but mine was the first and is now the last. Nobody even remembers what it is. First powered by a light weight Fox 40, the engine developed a problem, it wouldn't quit using the throttle, just kept ticking along with the barrel completely closed. This presented a problem in the climb and glide event, so it was replaced with an Enya, plus tail weight to balance the heavy engine. I even won some events with old Martha, now enjoying a much deserved retirement, only flown maybe once a year. Untold engines and radios have experienced Martha's tender mercies, last test engine was an MDS 40. That stands for Mostly Dead Stick. One of those emergency landings was into the Black Hole, which wiped out the landing gear and I had to make some repairs. If this landing gear departs the plane, I'll have lots more problems than landing gear. Current test engine is an OS 46, maybe just a little too much for Martha. I had to add balance weights to the ailerons to prevent flutter. Wide open, she's now a little too much for me too, and I fly her mostly part throttle. Headed straight up, she will accelerate until quickly out of sight, however glide is like an F-104, so it doesn't take long to be back on the ground. I've since had to re-cover the wing, sunlight having turned the MonoKote brittle. Stars are from the first flight, which overshot the runway into the stubble, punching holes in the wing. Stars filled the holes. Your plans, later than mine, look accurate except for a larger rudder. Your version may need this, as mine is reluctant to spin. If you want a fun airplane, give Martha a try, a good 25 is plenty of power. [See more pics 005, 006.]
DougSmith - 23/04/2018
As for the rudder, mine has has the original straight rudder, the triangle shape must have been added later. When in doubt, just use the big one and if it needs to be modified just cut it off.
DougSmith - 24/04/2018
The Miss Martha was designed by me in 1979. This was in the earliest days of fun-fly competition, for which this plane was designed. The plans here are not original, but do appear to follow the original outline except for the rudder - I don't know where that came from. The original airfoil has a slight amount of reflex at the trailing edge, but had problems with flutter at high speeds. The cure for the flutter was to add counterbalances at the tips of the ailerons, which consisted of 3/32" music wire and wheel collars for weights. (the original plans showed this). The last MM I built was in the mid 80s, and had an OS 61 four stroke. The best flying ones, IMHO, were ones built very light and with an OS .32.
Bob R - 03/01/2019
Thanks for adding your comment Bob. It's always really interesting to hear from the actual designer of a plan.
SteveWMD - 04/01/2019
Thanks, Steve. And if anyone is wondering where the name came from, I named it after my then girlfriend. She was a little miffed when I was spending so much time working on the design, so I painted her name on the side of the prototype and started flying in fun-fly contests. I had not intended to call it the Miss Martha, but the name stuck. She must have thought it was cool to have a plane named after her. She married me in '83 and we have been together ever since.
Bob Richards - 07/02/2019
That's a lovely story, Bob ♥ Say hi to Miss/ Mrs Martha from me!
Mary - 16/02/2019
That is my Miss Martha in the main pic (white/green/blue trim). What an awesome plane! Will do 100mph tumbles or snaps yet land at a crawl with no bad habits whatsoever! She will also do the nicest flat spins-both upright and inverted. It's an easy build and one of my all time favorite planes. Give the Martha a chance - you won't be disappointed!
flygilmore - 06/03/2019
I’ve downloaded this plan and want to start building this winter. Does anyone perhaps have the building instructions please? Uk based.
Jack - 28/11/2019
The Miss Martha is a great flying plane. I built one from an original kit. An average .46bb will turn it into a rocket. I met Bob at a swap meet once, super nice guy!
Chuck Lackey - 23/04/2020
First, thanks to Bob Richards for the design. I built a Miss Martha in 1993 from a kit that was available from the Model Engineering company. It was a remarkable airplane in the air. However, mine could be terrifying on the takeoff roll. I don’t believe it was a design problem, but rather my choice to overpower it with an O.S. 46SF on a soft mount. Regarding Jack’s question. My kit came with plans that included some notes, but did not come with instructions. I could provide photos of my plans if that would be helpful.
EricJ - 20/08/2020
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