Martin McIntosh

You may have been looking at some of my many build blogs. I use thin Zap for as much as possible. I have seen many builds with dozens of pins holding stuff together overnight; no need for it these days in most cases.

I must agree with Jon this time. A 1930`s bipe with an engine of the period was not exactly overpowered. I have been lucky enough to have flown in and actually looped a full size one. The dive angle before the loop was very steep and quite frightening so a scale model should replicate this. Mine has had a 155 for most of its life and on an 18x8 (still flying with the original one) was fine but I needed to pinch it for an overpowered Spit which donated its 180 to the Stampe, no great difference other than it now has more authority in loops and bunts. Most of my flying with it is as scale like as possible with the motor on 1/4 throttle burbling away to create a pleasant sound. The taps are only opened for loops and rolls and to climb for a spin. Anyone who watched the old Rothmans team will remember that they had to spend a long time regrouping when split up because the aircraft had a fairly constant speed.

Household spray on mould remover is very effective.

MK, does that not give you problems glueing them to balsa or do you use latex?

The peel ply I have used came from East Coast Fibreglass and is very much thicker than the stuff in the video (dress lining, white with red stripes). Probably made the mistake of not adding extra resin but it took a lot of sanding work out on flat surfaces.

MK, why bother with SLEC since you can select your idea of light balsa and not rely on them. All of the main ribs can simply be made the same using the block method. I just cut a couple of ply ribs from one of the kit upper ones to use as templates and made them in four batches which took no more than an hour to do. I use four aileron servos so the wiring holes can be cut out at the same time, much easier than messing with interplane linkages and each can then be adjusted individually. Got mine down to 6.25kg with the 155.

I bought my kit from Ali Mac who had a pile of old kits at the time and what he thought was a Laser 100 but it turned out to be an 80 so took it back and went to see Jon for a 100. He said that it would be inadequate but had one of the new 155 long strokes available so I got that. Later swapped for a 180 which takes it round loops better on the same 18x8 prop. I cut the exhaust stub down to save removing it if I needed to get the cowl off. Throw away the die crunched 1/16th ribs and make new ones from light 1/8th; also fit 1/8th birch ply dihedral braces. (you can bend the ply a bit for the sweep back and taper the spars to fit). The wing tips were particularly tricky because the supplied ribs would not fit and there are a lot of ply parts to fit together. Pay particular attention to the tail incidence because I believe that there were two versions of the plan and guess who got the duff one. I have to fly mine with a huge amount of down elevator trim but this does not affect loops and bunts. Before you even start on it think carefully about where the tank is to go, remembering that the model was designed for a short two stroke so you won`t be able to fit a 16oz one. Put the u/c elsewhere. My retro solution with a 9oz feeding a 6oz works very well whichever way up the model is and is shown somewhere way back on here.

Sorry, I meant acetone!

PTFE is unlikely to work. Even OS fitted tubing on their 26fs.

I tried the MRM finishing epoxy because I wished to spray my Stampe cowl with it. Supplied in tiny bottles only it would have been ridiculously expensive to do a whole model. To my surprise they recommended 50/50 cellulose thinners for spraying; this works with skinning resin which is basically the same thing. Once tried epoxy thinners but it was very slow to evaporate off and more than 10% inhibited setting altogether, same went for meths. Acetone is great for cleaning pots and brushes but I would not try it as a thinner. IPA is usually sold by the gallon as a nail varnish remover but this probably has a water content of around 10% so not pure enough. You certainly would not wish to thin down skinning resin anyway otherwise the cloth would not adhere. West System resin is by far the best bet.

Chris, just as an aside, what size was your Hurri and what did it weigh? I built a TN 72" spit from laser cut parts which were just heavy junk and it turned out at 18 lbs, originally for a 30cc petrol which was too large to fit in so got a laser 180 which powered it fine but landings could be a nightmare. Built another the way I would do it with a loss of 4 1/4 lbs with the same gear etc. 180 too powerful so fitted a 155.

Bert, from what I have seen of those linkages I would not even dare to commit it to flight. Those pull pull wires need to go through the tubes for a third time, no need then to even crimp them. That simple ARTF type screw on throttle link is just asking to work loose over time due to the screw denting the soft wire, especially with vibration present. Sorry to be so critical of what otherwise appears to be a good model.

I remember looking at the Nats F4C winning Hurri a few years ago and the guy was relying on a fan, presumably from a turbine, to cool his engine but he had the front end in bits between flights when I saw it. Seemed to rely on airflow from behind the spinner but have no idea where it exited. I would have thought that an i/c motor would be running too slowly for a fan of that type to be effective.

Cannot remember now how I fitted the 52s in mine. Even though it seems to be a very large model, there is very little room in the cowls (grp in my case). I think that I still have the not so good female mould so if you tell me the H x W x W I can check it. May be useful before you commit yourself.

If you use a lot of these then, The Component Shop sells packs of 50 pairs of genuine JR/Hitec connectors, also several gauges of twisted wire.

I use digital luggage scales which easily weigh a 25kg suitcase. About £3 on ebay.

I shall repeat that I have a £500 Molex tool to do these and many years of professional experience with them. Just send me your cable and connectors and they will be made up FOC.

Depends on if you want an accurately aerobatic model or not, and whether it is high or low wing. Generally, low wing high tail or vice versa. It can greatly influence knife edge flight although there is much more to it than that. Most current F3A types are mid wing/mid tail. On a simple fly about model you probably would not notice any difference.

Tested the motor today, it is capable of going like stink and idles just fine. Laser 5 used because it was in my field box.

I have had no reason to look at the head shims, did not think of that one but it is a possibility and would explain why I could not tune the top end on a pipe. My OPS 60 Resonanzas all ran on straight, being of very high compression. Dave now stocks Beckra 10 but I do not know what else.

Very puzzling as to why two out of three would not run properly on straight fuel which is all I used to use on ABC motors.

Thanks Peter. The first STX60RE was bought around 1980 for next to nothing. It went in a Dalotel, piped with copper tube S bend and may have been the best motor I ever had, first flick starting and straight castor fuel. Smashed to bits after nine years when the wing gave in. Much later I got two from M&R built up from spares. I replaced the carbs with Webra Dynamix ones as before, the reason being that I used crankcase pressure via a TK regulator but the main needle would not close down sufficiently on the Mag carbs. However, I could not get them to run properly. Accidentally filled up with 20% nitro one day and bingo! Don`t ask me why this should be so.

Done it at last! Between the two of us we finally got the piston in but it was very tight in the bore despite a ring gap being visible. When attempting to get the con rod to engage it fell out again. Abandoned the thing in disgust and went to the pub. This actually gave me the opportunity to scour the bore with steel wool and some headlight polishing pads. Got it back in the bore, now freed up, and managed to engage the con rod. Compression is good and I see no reason why it should not run OK. Thanks again for all your suggestions.

Thanks Peter. The first thing I do is to ensure that the ring groove locates fully over the pin. The problem is the ring tension preventing me from engaging it fully into the bottom of the sleeve using my thumb nails. It nearly gets there but not quite and I can still see a ring gap. Dave suggested that I try a little thick oil rather than the WD40 I have been using, also heating the sleeve a little to expand it. Rather reluctant to freeze the piston and ring to shrink them in case the ring gets brittle and snaps, but it may work. May get the owner to come round before I continue so that he can call the shots.

Please see my post above which explains all of this, and why I cannot now check the ring in the sleeve. I do not believe that it is a gapping issue. Spoke to Dave W. today and he more or less agreed that these have very high tension and can be difficult. Would not care so much if it was my own motor but has already cost my mate 25 quid!