Martinsyde S.1 (oz12559)

About this Plan

Martinsyde S.1. Peanut scale rubber model.

Quote: "This 1914 British design is more successful as a Peanut Scale model than it was as a WWI fighter/reconnaissance aircraft. Simple design makes it a fine choice for a first-time Peanut biplane.

In the fall of 1914, the Martinsyde Company introduced an airplane that surely must have caused charges of industrial espionage to flutter around Blighty. As you can see, the Martinsyde S.1 looks very much like a Sopwith Tabloid, except it's got a real landing gear! Yes, the nose moment is still tiny, and the stabilizing surfaces could always be bigger, but those accident-prone nose-over skids that Tabloids have are gone!

Sad to say, the Martinsyde didn't have much of a career. About sixty of the 80-hp Gnome-powered craft were ordered, deliveries taking place until October of 1915. Only six of the ships made it to France, where they were not well liked due to the poor lateral control furnished by the S.1's tiny ailerons. To add insult to injury, the Martinsyde was slow (87 mph) and climbing performance was poor. The narrow landing gear must have made ground handling a bit thrilling, as well.

After flunking out in front-line service, some S.1's were sent to Mesopotamia, where sand and indifferent maintenance further degraded their performance. The S.1's last chance at front-line glory came when a few of them were armed with an assortment of bombs, grenades and incendiary darts for use as anti-zeppelin aircraft. One S-1 based with No. 6 Squadron, Royal Flying Corps, is described as having been armed with a Lewis gun carried on the center section.

Later versions of the aircraft employed an angular Bristol Scout-ish horizontal stabilizer. To further complicate the issue, very early examples used a cumbersome four-wheeled undercarriage. I simply built the version that I thought was the prettiest.

In my version of the aircraft, the stab and rudder have both been enlarged, and the dihedral increased to 5/8 inch per panel. Peanuts are, after all, flying scale models and, if a bit of judicious tweaking will increase my odds of success, I'm inclined to tweak away.

While not a beginner's aircraft, the Martinsyde is a fair flier and can be made to fly with less heartache than some. The rubber motor is admittedly short. My feeling is that a short motor in a light airplane is better than a longer one in an airplane that has to carry performance-robbing ballast.

FUSELAGE: Nothing fancy here. Build the sides over the plans, and on top of each other, in the usual manner. Note that the cabane struts are part of the fuselage. If you cut them carefully, assemble the fuselage with temporary bulkheads, and check alignment carefully, you will build in one degree more positive incidence in the top wing than in the bottom wing. Gurus tell me that this will allow the upper wing to stall before the bottom wing. The bottom wing keeps on flying and, being further aft, effectively adds to the nose moment, bringing the nose back down. I dunno, it seemed to work for me.

Use stiffish 1/20-inch balsa for the longerons, cabanes and motor-peg-mount, and softer stock for uprights and crosspieces. The sheeted portion of the fuselage is made from very light 1/32-inch stock, and the stringers are 1/32 x 1/20 medium. The forward bulkheads (to the point where the stringers start) are soft 1/20, while the two aft bulkheads are soft 1/32 stock.

WINGS: The top and bottom wings are identical, with some minor differences in the center section. The solid lines shown on the plan in the rear of the center section show the construction for the upper wing; the dotted lines are for the lower wing. There is, naturally, one exception to this rule. The piece of 1/8 x 1/20 that is shown in the rear of the upper wing's center section (part of the cabane attachment structure) should be duplicated in the lower wing and will form the attachment structure for the rear ends of the landing gear legs. The leading edges are made from springy 1/16 square stock, the trailing edge from soft 1/20 x 1/8 and all ribs from soft 1/32 sheet, except the ribs in the center sections and at the strut attach points. These ribs are made from soft 1/20 stock. The wing tips are two laminations of 1/32 that have been soaked in water, glued and bent around a waxed cardboard form.

TAILFEATHERS: Remember, this airplane has no nose. Keep the tailfeathers light. If you don't automatically weigh your balsa, now is a fine time to start. I used 5 lb. stock. Once again, the outlines are formed from two laminations of 1/32 x 1/20, soaked and bent around a waxed cardboard form.

MISCELLANEOUS: The landing gear legs are made from some 11 lb., 1/20 stock. The only wire in the gear is some .020 that is sandwiched between two pieces of 1/32 and forms the crosspiece. The wheels are two laminations of soft 1/20 stock that have been bushed with small pieces of 1/16-inch birch dowel. The inner wheel covers are discs of bond paper that have been covered with tissue and glued to the wheel. The outer wheel covers are larger discs from which a pie-shaped segment has been removed, allowing them to be bent into the flat cone shape shown on the plans. The cowling is fabricated by the time-honored method of choosing a soft block of balsa and carving away anything that doesn't look like the cowling. I did some additional hollowing of the finished block as well, more to give me room to install dummy cylinders than to reduce weight. The cylinders are the smallest Williams Brother's models, gussied up with balsa heads and wire pushrods and spark plugs. The prop is a 4-3/4 inch Peck unit. I'm not out to set any records with this airplane, and the Peck prop is very durable.

FINISHING AND COVERING: My references showed about six photos of the Martinsyde, all in that wonderful shade of gray that exists only in WW-I photography that could equally well represent khaki, olive drab, doped linen, or metallic magenta. I made a judgment call and opted for "antique." To get this mysterious parchmenty shade, I used Dr. P.H. Martin's Radiant Transparent Water Color (yellow ochre) applied to the tissue with an airbrush. First, mount the tissue in a shrinking frame of some sort. Then mix 1-1/4 oz. water, 1-1/4 oz. isopropyl alcohol, 2-3 drops household ammonia and about a quarter bottle of Dr. Martin's in a 3-oz. airbrush bottle. Spray this mix on the tissue. The first coat is awful - but have faith. Allow it to dry and repeat until you get a nice "aged" look. Do let it dry between coats, as it's hard to judge the shade you're getting when the tissue is wet. Though the photos don't show it, I got a bit carried away and my Martinsyde is, I'm afraid, a bit more orangey than antique.

The nose block and the portions of the fuselage shown in the photos are silver. The numbers on the rudder are black and the Union Jack consists of a blue field with broad white crosses and thinner red crosses superimposed on them. These markings, by the way, appear on an actual Martinsyde S.1 shown in War Planes of the First World War, Volume One: Fighters, by J.M. Bruce. The wings have no spars and, if you were careful, the tail surfaces are very light. This translates to a gentle application of alcohol to shrink the tissue, followed by pinning the flight surfaces to a flat surface until the alcohol dries.

ASSEMBLY: Meditate for a while, since itty-bitty bipes are a pain to assemble. If you've been careful with the fuselage assembly, careful with the lengths of the cabanes and careful with the alignment of the fuselage sides, you shouldn't have too much trouble. Another big assist comes from leaving little "nubs" on the cabane and interplane struts. Then I use a needle file to drill holes in the balsa mounting positions in the wing center section and outer wing panels. The strut "nubs" then glue into the holes. I find this locks the structure in place nicely. If you've got a better system, by all means use it. I put the tail-feathers on first (using a piece of 1/32 balsa under the stab to provide the decalage called for on the plans), then the lower wing (measuring between the stab and the wing to assure myself that the wing is aligned properly with the stab), and then finessed, tweaked, teased and torqued the upper wing to fit. The interplane struts are added last. This is a fine application for a Titebond type of glue, as you'll want time to move parts around. Last, the landing gear is installed.

My ship weighed just under ten grams, sans rubber and ballast.

FLYING: I firmly believe that no two Peanut scale models of the same aircraft exhibit the same initial flight behavior. Given the size of the models, I'm not sure that one fellow can really duplicate another's weights, incidence angles, etc. In any event, here's how my Martinsyde behaved: using a loop of .10 inch rubber about twice the hook-to peg distance, I needed a lump of lead putty (great stuff, found in fly-fishing stores) about 3/4 the size of a pea to bring the balance to the 20% point on the upper wing. Powered flight showed a pronounced power stall-spin to the left. I added down and right thrust, and wash-in on the left wing panels. Then a tad of left rudder was added to help the turn.

I found the Martinsyde to be challenging enough to hold my interest, without being difficult enough to make me think about taking up origami. With its old-timey looks, it's a great crowd pleaser, as well. I hope you enjoy your Martinsyde!"

Direct submission to Outerzone.

Quote: "Peanut scale Martinsyde S.1 by John Berryman from the May, 1989 issue of Model Builder. Entire wing and horizontal stabilizer have been redrawn, for accuracy."

Supplementary file notes

Article.
Transcript.

Corrections?

Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction