Plan Build Models

Lacey M10

Maurice Ashby  |  May 12, 2009

You can order the Lacey M10 plan at www.myhobbystore.com

When Joe Lacey designed and built his little M.10 back in the late 50s and early 60s for the American home-built market he couldn't have imagined that it would become more popular as a model than it ever did as a full-size. Although hundreds of plans ($8 per set) were sold there was only one other example constructed. Why this should have been is a bit of a mystery, especially as the M.10 was the runner-up in the 1962 EAA design contest.

As a model, however, the design has been a tremendous success. Hundreds (if not thousands) have been built for free-flight, indoors and out, and it has triumphed in many competitions.

The aircraft is fairly simple in layout and has a certain charm of its own, which tempted me to draw up plans for an R/C version. I'm certainly not the first to do so, I remember a larger version some years back in an American model mag. My design is what I would call semi-scale sport, and although the basic outline is not too far out, a few items have been altered, i.e. the wing section, whilst ailerons have been enlarged, as have the fin and rudder areas.

The model spans 40" (1/6-scale) with an all-up weight of 3 lb 2oz, giving a wing loading of 16 oz / sq. ft. As you can see the model is of built-up construction, using medium-soft balsa for most of the structure apart from spars etc.

PAWS FOR THOUGHT

I originally intended to use a .25 glow engine for power, but changed my mind in favour of a P.A.W. .19 diesel that was lazing around doing nothing. As far as a neat installation was concerned things couldn't have been better, with the 19s silencer being very easy to conceal. After the first few test flights, however, I realised that the Lacey needed a bit more grunt. That's not to say the P.A.W. wasn't man enough, it's just that I envisaged a fairly brisk aerobatic performance... I can hear the mutterings, Yes, but its not that sort of aeroplane! And I agree to a point. But, when you look at the layout of the models low aspect ratio wing, short moment arm, and large (ish) elevators and ailerons, it's crying out for power. Besides, with such a light airframe I even thought it might make a good fun-fly. Anyway, the P.A.W. was returned to its reverie in favour of my trusty S.C. 25 glow, and the transformation was immediately apparent. Were now dealing with a sort of clipped wing Cub-type pylon racer-come-aerobat. So, you have a choice - either pull the noise lever back and chug round sedately, or go for it.

Flying wise I'm still experimenting with control surface throws, but set as shown you'll find that loops, rolls, spins etc. are no problem. The take-off is straight with minimum correction needed, followed by a brisk climb. Landings are normal with no nasty tendencies, and the dead-stick glide is very good indeed.

So, that's the sales pitch delivered - tempted? If you fancy having a go there's some satisfying building involved, and at the end you'll have a model that's a bit different. How many Laceys have you seen at the field?

ALL ABOARD
I always start building with the wing, having read somewhere that this gives time for it to cure whilst building the rest of the model. After all it is the most important part and needs to be straight. In truth, this wing is a fairly simple structure, and being only 40 span it can be built in one piece. You'll have to splice the wood to do this, making sure that the joints are equally spaced at the wingtips on each side. Alternatively, if you're cursed with a small building board, like me, you may have to build the wing in two halves and join at the centre with ply braces.

Begin by pinning down the two lower spars and the 1/16 sheet lower trailing edge. The front 1/4 lower spar needs to be raised by some scrap 1/16 to allow for the bottom l.e. sheet. Glue the 3/16 rear t.e. spar in place and add the ribs, not forgetting that the centre and tip ribs are 1/8 thick. Next, add the two top spars and the top t.e. sheeting, followed by the 1/16 vertical grain webbing, front and rear (note the webs are every other bay - see plan). Add the 1/4 leading edge and remove the assembly from the plan when dry.

If you've built the wing as one piece, then now's the time to add the top and bottom l.e. sheeting. Otherwise join the two panels at the centre and add the ply braces followed by the top, bottom and centre-section sheeting. The 1/8 lite-ply servo rails are next to be added. I used a Hitec mini servo for each aileron and found that, by fitting them in the bays indicated on the plan, the servo leads were long enough to go through the centre-section ribs and out through the bottom sheeting, allowing the use of a simple Y-harness to connect to the receiver. Its a good idea to trial fit the servos at this stage so that you can see how much of a balsa filler is required around the protruding servo to stop air entering the bottom of the wing (important, as air in the wing makes a difference to the trim). Two 1/32 ply wing bolt reinforcements are then added to the top and bottom at the t.e., plus a little wedge of balsa block between the t.e. sheeting for extra support.

Apart from a good sanding, that virtually completes the wing construction. The ailerons are simple to make from 11/4 x 5/16 t.e. stock, and can be hinged as preferred (mine are top hinged using hairy Mylar jobs).

TAIL FEATHERS

The fin, rudder and tailplane are straightforward enough and shouldn't need any explanation, just be sure to use a medium-hard grade of balsa.

FUSELAGE
This is built in two sections. The front is basically from 1/4 sheet and the rear from 1/4 square, to allow for the correct fuselage taper from the rear of the cabin.
Begin by marking out the upper front 1/4 sheet fuselage section (I normally use carbon paper for this job). Once you've cut the wing seating and front cabin areas to shape, pin this to the plan. Now pin the lower 1/4 sheet strip to the plan and add the 1/4 filler between F1 and F2 plus the three 1/4 uprights. When dry, remove the assembly from the plan and repeat.

These two front sides are now joined by formers F2 (cut from lite-ply) and F3 (built from 1/4 balsa). When you're satisfied that everything's straight, add the 1/4 ply engine bulkhead plus the four triangular support pieces. Lay this front half aside and build the rear fuselage over the plan in the traditional manner, i.e. one on top of the other, not forgetting to put some cling film, or whatever, between the two to prevent them sticking together (the backing sheet from Solarfilm is ideal for this purpose). When dry remove from the plan, join together at the rear and add the cross pieces - stand it on end and you should have something that looks like an electricity pylon! This rear section can now be spliced and glued to the front part to make up the complete fuselage. Add the 1/4sq. cross-pieces at the rear top and bottom.

It's probably easiest to fit the undercart at this stage, before sheeting the underside of the fuselage. The undercarriage is a fairly simple affair, made from 10swg wire bent into a V shape so that when the front end is up against the engine bulkhead the legs exit at the position indicated and against the inside of the fuselage.

At the position shown on the engine bulkhead, drill two holes (above and below) and bind the undercarriage to the bulkhead using strong nylon twine, then soak the lot in epoxy. Where the legs exit the fuselage glue a couple of hardwood blocks behind, then fill back and front with 1/8 ply. The fuselage underside infills can now be added using medium-hard 1/8balsa.

While the upper front of the fuselage is open its a good idea to fit the engine mount (side mounted, of course) and install the throttle cable. Now fill in the upper forward cabin area using 1/4 sheet planking and fit the 1/8 ply wing dowel locator. When the glues set make a trial fit of the wing, ensuring that the locating dowels are set into the wing l.e. at the slightly downward angle shown. Drill corresponding holes in the ply wing dowel locator and one for the nylon wing bolt. Glue the 1/8 ply wing bolt mount in position, centrally, under the bolt, then mark and drill for the captive nut.

ENGINE COWLING

The cowling has 1/32 sides that extend to the front of the cabin, whilst the inner pieces that locate against the engine bulkhead are made from 1/4. The finished item is held in place by four self-tapping screws.

A dustbin-type silencer would be ideal so as to avoid too much butchery of the cowl on the right-hand side. Unfortunately I couldn't find one suitable so had to modify the existing standard unit.

With the fuselage still uncovered its time to decide whether to use pushrods or snakes to operate the elevator and rudder. I chose snakes as I find them so much easier to install - they're simple to anchor and easy to set up.

RADIO

Standard size servos were used on rudder and elevator, with a mini servo on each aileron and throttle. Regarding the throttle set-up, I usually wind up sticking the servo to the inside of the fuselage with servo tape; try to get as straight a run from engine to servo arm as possible. There was a time when I would use multi- strand cable running in plastic tubing, but now find it better to use piano wire (say 20swg) running in tubing. Its easy to put a bend in the wire to link up neatly with the servo arm if needed.

Mount the aileron servos under the wing in the positions indicated. On the prototype they're located well within the wing with just the servo arm protruding. This made them difficult to box in, and in hindsight I should have mounted them with the lugs and the bottom of the wing, flush. Standard 16swg threaded wire pushrods hook up the aileron horn connections.

The receiver and battery pack are secured to the fuselage floor with Velcro; Ive found this method quite satisfactory, and it allows the battery to be moved around to achieve the correct centre of gravity. The radio switch is mounted just below the cabin line on the left side, away from the exhaust.

COVERING & FINISHING

The two full-size examples built shared the same colour scheme, white with red trim. All red with white trim would make a refreshing change - after all our subject is only semi-scale sport, so no need to be too fussy.

The range of covering materials available to us is quite vast these days; I opted for Solarspan, and have found it very satisfactory. When covering is complete, the tailplane and fin can be slotted in and glued - make sure all is square before the glue dries. Note that the fin extends down and is stuck to the top surface of the tailplane. Before hinging the control surfaces add the coloured trim to wingtips, tailplane fin and rudder. Solartrim is ideal for the fuselage lettering and trim lines, including the black cabin windows. One last thing - cover the wing end plates before attachment.

BITS AND PIECES

The steerable tail wheel unit is a commercially available item from your model shop - use your preferred means of attachment to the rudder. Of course, you could use my method, which was to use a small rubber band that works as a shock absorber between a hook bent in the operating arm and one fixed to the rudder (see pic on page 63).

The fuel tank used was a SLEC 4oz square (blue), however, the tank bay is fairly cavernous so a larger one will fit very easily. To hold the tank in position (centreline of tank in line with needle valve) use thick plastic foam sheet all round.

That wraps things up as far as the buildings concerned, all that's left to do now is fly the beast!

NUFF SAID!

To be honest there's not much more that I can add to what I said earlier on the flying side of things. The model is amply powered with a good .25, so don't be tempted to fit a .40 (someones bound to, nevertheless!) If you fancy dabbling with the performance envelope then maybe you could give flaperons a try. Ive had a go at coupling rudder and ailerons, which warms things up a little. Whatever you do, the Lacey is one of those models that can pretty well become whatever you want it to be, so experiment and have fun!

DATAFILE
Model type:  Semi-scale sports
Wingspan:  40''
Wing area:  450 sq. in.
All-up weight:  3 lb 2oz
Wing loading:  16 oz / sq. ft.
Engine (recd): .25 two-stroke
Engine used: S.C. .25 two-stroke
Propeller used: Bolly 91M2 x 6''
Radio: 4-channel, 5 servos
Control functions: Aileron, elevator, rudder, throttle
Control deflections: Ailerons ±1M4'', elevator ± 1M2'', rudder ± 1''

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