John Stainforth

IC glow engines are far from extinct. OS and Saito still carry a reasonable range in the useful sizes. Personally, I think the smell, mess and noise are all exaggerated, as is the cost of the fuel. In most of the clubs I have visited, members have been very happy to retreat to a nearby pub and spend more on beer (which, let's face it, is very bad value for money) than they have on glow fuel at the flying field.

Have I just been lucky?! RCME always comes up for me in a split second, even on my crummy Tesco phone.

Epoxy setting times are very strongly temperature dependent. When I was living in Texas in a moderately air-conditioned house - internal temperature perhaps 28 + C in the summer - 30 minute epoxy would go off in about 10 minutes, so I was sometimes confronted with a race against time. Because epoxy setting reactions are strongly exothermic, one also has to beware of thermal runaways in any climate, if the epoxy is mixed in a small container with a small surface area: the mixed epoxy can heat up very quickly and set in a flash. This is particularly the case with finishing resins, which have to be decanted immediately after mixing, into a small tray with a large surface area to prevent this happening.

Personally, I think downthrust is completely unnecessary in RC models. It's a hangover from the days of free-flight and single-channel RC models where we were could not adjust the trim in flight. All one has to do to stop a plane climbing under power is reduce the angle of attack by elevating the model down with either the elevator or the elevator trim. This reduces the lift and the drag; no need to reduce power at all. The way to fly a model as fast as possible in level flight is to have the thrust line straight through the C.G. with the plane trimmed to fly level on full power.

It's splitting hairs, I know, but in terms of mass the amount of CO2 produced is slightly greater than the H20. (RHS of eqn: 88 + 72 += 160 mass units = LHS). But still the point is well made that combustion produces lots of water (hence contrails from airliners).

It is worth remembering that before about 1955 every car, ship, plane and all science and engineering was done with slide rules and log tables. War bird airframes were accurate to 1/16th of an inch. The highest precision in engines was the hallowed thou. When I was at school in the sixties we did all our scientific calculations with logs and slide rules. Actually, my experience was much like yours: we were taught to do order of magnitude estimates first, to reduce the risk of screwing up with the slide rule, which came next. Then, finally, log tables. I still do order of magnitude calculations all the time in my scientific work.

A good a starting point is indeed the manual for the OS46X or 55X. If you do as they say, you really can't go too far wrong. If the engine does not start and keep running there is either a fuel supply problem, or a glow plug/battery starter problem, or you've got the needle valve set very badly out. The tuning of glow engines is pretty straightforward.

I have these wonderful motors that run on liquid fuel and generate their own heat!

I usually start with a pair of diagonals (from the leading edge), then 2 pairs of straights, then 1 or 2 more pairs of diagonals, i.e., 8 to 10 bands in all. The final diagonals keep the underlying bands pulled inwards on the dowels.

They should be inserted on the underside, i.e., between the servo tray and the lug (as per instructions!)

I have a Hanger 9 Spitfire with an Saito 100 4s, originally with a 14 x 8 prop. I changed this to a 3-blade 13 x 8 - I can't remember why! It certainly wasn't for scale looks because the 3-blade looks even more obviously too small than the 2-blade. Maybe it was for better ground clearance. Anyway, the interesting thing was that I didn't notice any drop in performance at all; I even got the impression the plane had more oomph with the 3-blade than the 2, but these things are very subjective. The main cost was the aluminium spinner.

People tend to be rather choosy who they bare with!

I have never had to warm epoxies in the UK. That may be a hangover from living in hot climates, where the problem is the other way round: epoxies set much faster than expected. For finishing epoxies, one has to be very careful (even in the UK) if one mixes them in small mixing jars that have a small surface areas, because a thermal runaway can easily occur that makes them set in no time at all. So, I always decant the mixed epoxies into trays with a large surface areas that prevent them getting too warm and setting prematurely.

One thing you can do is cut a female template of the profile of the LE in a piece of thick balsa and use that to continually monitor your progress while you are sanding, to avoid over-doing it. This is an ideal task for a Permagrit sanding block.

There is nothing more disappointing than spending days building wings and fuselages for them to come out warped. (I learned this the hard way as a child.) So my view is that some kind of jigging for both wings and fuselages is highly worthwhile. It does not have to be sophisticated, just fit for purpose. It is very satisfying to set up a build so that you know it is going to come out more or less dead right, because you have ensured that it has no where else to go. This takes surprisingly little extra effort. It's in the same spirit as measure twice, cut once; or better still, measure four times, cut once. Let me put it another way: when I have left things to chance, they often or usually turn out badly.

Silly me, I stick to roughly what the manufacturers recommend. I was using 18% nitro 20% oil in the US for Saitos. Here I am using Optimix 15% nitro 4-stroke fuel; not sure what the oil % is. For OS, I use their recommendations; for Lasers, I follow Jon's advice.

What is worth doing is to trim the edges of the pieces of sheet to be joined with a very sharp knife along a steel straight edge. Then the two halves will fit together like a glove. I put CA along the back of the joint, which wicks into the joint - so sanding the other side is almost a non-issue. Done that way, the joint is almost invisible.

Personally, I would put another crossbeam across middle for extra resistance to curvature.

Ha! As Dave Platt said jokingly [if you try pinning] "it's hell on the thumbs!" Instead use weights, masking tape, and custom made jigs superglued straight on to the glass (as in the picture).

I am completely won over to building on thick plate glass, which is dead flat, as advocated by Dave Platt.

Jon, We've had recommended various solvents for cleaning old engines - diesel, petrol, antifreeze, etc. What about WD40, because I imagine that would be pretty effective (but I have not tried it)? I wondered if you had any experience with that.

I do the same, but with CA. (Actually, one doesn't really have to open up the join with CA, because it wicks into the joint.) I generally use far more aliphatic glue on models than CA, but this is a near-perfect application for the latter.

No balancing stand! The velcro is just to mark the CG position.

A thin strip of self-adhesive velcro, stuck onto the underside of each wing, also does the job.

Surely, the preference for two or three tubes depends on the accessibility of the fuel-to-carb tube? If it's easily accessible, two tubes for me; otherwise, three.