Hints and Tips

Choice of subject

For the beginner to free flight scale modelling, the decision as to which aircraft type to model can have the biggest effect on whether the project is a success or not. Choose a tricky subject (from the construction or flying point of view) and you could be put off for life. I would also recommend not building a scale model until you have built and flown one or two sport models, to learn the basics of building, covering and trimming - these tend to be more forgiving than scale jobs. An ideal first subject would be a high wing monoplane with flat fuselage sides, and a minimum of stringers. The high wing gives maximum stability, and the simple structure makes building simpler, and keeps the weight down. Perhaps not as glamourous as a WW2 fighter, but hey - we can work up to that later - let's get a successful model or two under our belt first!

There are lots to kits choose from, but beware - the wood selection in some is not ideal (often too heavy), and many serious modellers replace much of the stripwood (and even sheet) with lighter material from their own stocks. Some kit propellers are also not the best design to achieve maximum duration from the rubber motor (too little blade area is common). Against this, all the parts you need are there in the one box, and you don't have to worry about transfering former shapes etc. onto balsa sheet.

Plenty of choice amongst available kits - a couple of suggestions from the ranges I have experience of (thinking rubber powered, outdoor, somewhere in the 20 to 30" span region) would be:

Airsail (a New Zealand firm) produce a very nice 28" Pilatus Turbo Porter, and 20" Auster AOP 9 - both with die-cut parts.

West Wings in the UK have an excellent 24" span D.H.Puss Moth in their range, which flies well. Aerographics (another UK firm) produce an Auster J4 kit and this has been joined recently by a 20" span Lacey M-10, which as well as being a nice simple shape, is an extremely good flier.

Hacker Models produce three very complete kits that would be ideal first subjects. There is a Piper Cub, D.H.C.Beaver and Champion Citabria. All parts are cut out and ready laminated balsa outlines are even provided for the wingtips. All three are designed primarily for CO2 power (the Gasparin GM 120 being the recommended power source), but they are easily converted to rubber power.

This should not be thought of as a definitive list by any means - there are plenty of other fine flying kit models out there - these are just one or two suggestions.

I was brought up with the Keil Kraft and Veron Flying scale ranges, some of which can be made to fly very well if built carefully, and the dreadful propellors replaced. They always were rather heavy though, unless you changed the wood, which was usually of the "heart of oak" variety. Most of my childhood efforts managed nothing more than a brief hop, but the aeromodelling bug bit, and I haven't been able to stop since! Experienced modellers might like to have a go at the Veron Tiger Moth and Sopwith Triplane sometime - they both are great fliers. One pair of wings is probably quite enough to be worrying about though if you are new to the hobby!

Building Hints

One or two thoughts:

Cover your plan with clear plastic film to stop the glue sticking to it (e.g. slit open a plastic bag)

When building a fuselage frame, build one over the plan, then cover with plastic film, and build the second half directly over the first - that way they come out exactly the same shape and size

Use a sharp knife, and when making a cut, stick to that old adage, "measure twice, cut once"

Use glue sparingly - it is a lot heavier than the balsa.

When joining the fuselage halves together, to keep them at 90 degrees to the building board, use something like a set square or block with right angle corners on the outside of each frame. One thing that works well is to use those plastic floppy disc boxes that you get when you buy 10. If they are full of discs, the weight of the box is often sufficient to hold the fuselage frame in position.

If you are building a plane with fuselage stringers, scallop out the formers between each stringer after assembly. This prevents them showing through the tissue, and also saves weight.

If your model has a parallel chord wing, so all the wing ribs are the same, I tend to cut a master rib from ply or plastic card, then use this as a template to cut a pile of identical ones from balsa.

Concentrate your weight saving efforts on the rear of the aircraft, especially for a rubber powered plane - if you can make the back really light, this will minimise the amount of noseweight you have to add to balance the model. Half a gram at the back can save 1.5 grams at the front!

After tissue covering the model you will want to water shrink the tissue. Old perfume or Eau de Toilette sprays are very suitable for this task, allowing a fine water mist to be applied. Don't forget to hold wings, tailplanes and fins flat while the tissue dries, otherwise warps can occur. My method (if you can call it that) involves placing the edges of table mats under the leading and trailing edges, leaving a gap underneath the wet part, and balancing small spice jars around the edge of the part to keep it weighted down (high tech, eh?)

When dope is applied to the tissue, make sure it is well thinned (at least 50/50 with cellulose thinners). If you add a couple of drops of castor oil to the jar and mix it in, this acts as a plasticiser, and helps to prevent warps. As with water shrinking - hold your parts flat while the dope dries.

Trimming Aids

When you first come to take the brave step of throwing your newly completed masterpiece at the scenery, it is very unlikely to glide along beautifully straight away - some adjustments are going to be needed! Before you start adjusting anything, make sure the centre of gravity (balance point) is close to the point shown on the plan. Having it too far forwards is less of a problem than having it too far rearwards (a forward c of g actually helps stability).

Probably the most common way of allowing for adjustment on the tailplane is to fit it in a slot through the fuselage that is wider than the thickness of the tailplane. It can be held in place with balsa or ply shims. These can be moved around during test flights to either elevate the rear of the tailplane to correct the model diving, or elevate the front of the tailplane to correct a stall.

Another method of allowing for adjustment is to make the elevators and rudder as separate parts and attach them to the tailplane and fin using hinges simply made from soft wire. This does add a little weight but looks neater, and makes adjustments simpler. Once the correct positions have been determined, a drop of superglue (cyanoacrylate) will lock everything in place. My own experience with this method is that it works great for small models such as peanut scale models (13" span), but can be a bit sensitive on larger models. The large size of the elevators can mean that a very small adjustment makes a big difference to the trim of the model. What I have now started doing is adding movable trim tabs to the tailplane, fin and even the wings of low wing models. I try to put these in a similar position to those on the full size plane, but make them rather larger. These make fine adjustments to the trim easier to make. The wing trim tabs are useful for helping to keep the outside wing of an aircraft down in a turn - for example, imagine a plane circling left - you do not want the left wing to dip, so you bend the trim tab on the right wing up. This has two effects - firstly it reduces the average lift on the right wing, and secondly (perhaps more importantly) increases the drag on the right wing. Both these factors should help prevent the left wing from dropping. On high wing (more stable) models, these tabs are rarely necessary.

Once low powered flights are looking OK, and longer flights are attempted, it may be found necessary to start adjusting the thrustline of the prop. A common reason is the appearance of "power stalling" - the model stalls under high power, though not on the glide. Most models seem to need a at least a little down and right thrust, so I usually build some in. On a rubber model this simply means glueing in the nose bush at an angle - stick a long bit of wire through it so you can see the angle relative to the fuselage. Later adjustment is traditionally by shimming behind the nose block with thin ply, though adjustable bearings are now commercially available. On models using a power unit other than rubber (eg. CO2, Electric or Diesel) it is a case of angling the mounting bulkhead or bearers, or just shimming with washers. In is important to be able to easily get at such power units "in the field" to be able to adjust thrust angles if necessary - do not bury the motor inside the model with only a small access hatch, and remember you will need to get at both sides of any screw fixings. On small models, access panels tend to stay in place with just friction, but you have scope to be ingenious with hooks, rubber bands, dowels or even press-studs!

Other random tips

One simple way to transfer printed patterns for formers, ribs etc. from a plan onto balsa sheet is to photocopy the relevant bits off the plan, cut them out and paste them onto a sheet of paper the same shape as the piece of wood you are going to use. You can stack everything as tight as you like to save precious balsa! Once satisfied, photocopy the result. Next take your new copy , place it face down on the balsa, and iron the parts onto the wood with a medium hot iron. The heat melts the toner and prints it on the wood. It is quite probable that the wood will curl up slightly - a quick iron on the back of the wood should bring it back. I tend to leave the wood to settle down for a couple of weeks afterwards before using it.

Another possibility is to again place the photocopy face down on the wood, then rub cellulose thinners onto the rear of the paper using a wad of kitchen towel.

Yet another possibility is to simply stick your final photocopy face up onto the wood using a spray photo mount adhesive, such as produced by 3M. You then have to cut through the paper and the wood together when cutting the parts out, but this actually helps to reduce splitting of the balsa. The paper is peeled off afterwards.

Simple black markings for a scale model can be produced on a normal photocopier by simply copying artwork onto clear decal sheet, as sold for plastic modelling. I did the small titles and logos on my Corben Super Ace like this, copying the artwork off the plan. If you need a white background, simply copy onto white decal sheet instead of clear.

A neat way of retaining a wheel on a wire axle is to cut a thin slice from a piece of aluminium tubing of suitable diameter, slip this over the end of the axle, and either apply a drop of cyano to the end, of simply crimp on with pliers.

Looking for a windshield for your latest model? - keep a look out next time you are in a supermarket - it is amazing what shapes you can find amongst the transparent packaging used extensively nowadays. I tend to hoard such material - if nothing else, it provides an endless supply of material to have a go stretch formed canopy moulding (and I usually need plenty of attempts before I get get one good one!)

When using a commercial plastic prop for a rubber model, check that it is balanced before fitting. Chances are that one blade will be slightly heavier than the other - the heavy blade will always stop at the bottom when you spin it on a piece of wire. Sandpaper the heavy blade using wet and dry emery paper until the prop comes to rest in a random position after spinning. A balanced prop will give a smoother flight.

Previous page

Next page

Back to home page

You are currently on page 57 of 75