John Stainforth

Don, OK, I am naming one with more. For my 1/5th scale S6b I am using an 7/8" x 850 mm F3a Unlimited Gator carbon fibre tube and sleeve that passes through 9 ribs in each wing panel and 2 ribs in each wing root: And there is also a small, much shorter rear wing tube. I don't see wing tubes as dead weights that have to be minimised. The tubes are superb (strong and light) spars that add considerably to the strength of the wings. So even if my design is overkill (which it probably is) I don't think the long wing tube is in anyway detrimental (except its cost!)

Many thanks to all for the feedback. I gave the wrong units for the cubic wing loading - I meant to say kg/m3 not g/cc. I could just as well have used imperial units, but I am a big fan of metric and air has a density of 1.225 kg/m3, so these metric units are rather easy to compare with that, e.g. a cwl of 5 kg/m3 means an aircraft that has an effective overall density about 4 times greater than air. I also made a small error in my approximation for the wing area of fighter jets in that I did not allow for their sweepback, so the cubic wing loadings are somewhat exaggerated - they should be reduced by about the sine of the angle of sweepback. I have used logarithmic scales for both the weight (actually mass) and wingspan axes of the plot. The equations of the straight lines are given by the power law M = cL^3, where M is the mass of the aircraft and L a measure of its length scale and c is the cubic wing loading, which has units of density. So the logarithmic relationship is log M = log c + 3 log L David, when I said that cubic wing loading does not have to be scaled, I only meant this was broadly true, and it certainly does not mean that we should give our scale models the same cubic wing loadings as their full-size counterparts. I agree with you about this: models of the heavy wing loaded fullsize planes would not be much fun to fly and would have to be flown unrealistically fast to stay in the air. My Hanger 9 Spitfire is one of those red dots on my graph and it has less than half the cubic wing loading of a fully laden full-size Mk 1 Spitfire. (The later marks of Spitfire had increasingly higher wing loadings). Likewise, I am building my model S6b to have less than half the cubic wing loading of the fullsize.

Interesting thread. For those who are not mathematically inclined I have made an empirical log-log plot of aircraft weight versus wingspan for a very wide range of aircraft from the smallest indoor models to the fastest full-scale jet aircraft. The thin lines are lines of equal cubic wing loading in metric units of 2, 4, 8 and 16 gm/cc. The small dots are monoplanes. The ones with the smallest wingspans (between 10 and 20 inches) are indoor model aircraft, and the largest are very large aircraft such as the B747 and An-124 and 125. Some of the full-size planes are highlighted with coloured symbols. The red circles about a third of the way up the plot are my own model aircraft. I was astonished to see that the smallest indoor flyers, and my own model planes, and the largest transport planes all plot around the same cwl line of about 4 gm/cc (let's call this the Boeing 747 line!). For some of the aircraft I have both laden and fully laden data and for these the fully laden cwl's are about twice those of the unladen (8 cf 4). All these data suggest that cubic wing loading does not have to be adjusted with size of aircraft. I also plotted data for a variety of birds (open circles) and was surprised to find that nature uses a very wide range of wing loadings. The lightest wing loaded birds are soaring birds with cwl's better than most model gliders. The heaviest wing loaded birds are those that can dive at great speeds (e.g. falcons), which retract their wings to reduce their aspect ratios. These birds have even higher cwl's than racing seaplanes (e.g. S6b), WWII fighters and the earliest jets (e.g. Meteor) . Only the fastest jets have higher cwls. The highest of all are the Starfighter, EE Lightning, B58 Hustler, F4 Phantom and SR71 Blackbird - but those are more or less flying bricks!

Interesting thread. For those who are not mathematically inclined I have made an empirical log-log plot of aircraft weight versus wingspan for a very wide range of aircraft from the smallest indoor models to the fastest full-scale jet aircraft. The thin lines are lines of equal cubic wing loading in metric units of 2, 4, 8 and 16 gm/cc. The small dots are monoplanes. The ones with the smallest wingspans (between 10 and 20 inches) are indoor model aircraft, and the largest are very large aircraft such as the B747 and An-124 and 125. Some of the full-size planes are highlighted with coloured symbols. The red circles about a third of the way up the plot are my own model aircraft. I was astonished to see that the smallest indoor flyers, and my own model planes, and the largest transport planes all plot around the same cwl line of about 4 gm/cc (let's call this the Boeing 747 line!). For some of the aircraft I have both laden and fully laden data and for these the fully laden cwl's are about twice those of the unladen (8 cf 4). All these data suggest that cubic wing loading does not have to be adjusted with size of aircraft. I also plotted data for a variety of birds (open circles) and was surprised to find that nature uses a very wide range of wing loadings. The lightest wing loaded birds are soaring birds with cwl's better than most model gliders. The heaviest wing loaded birds are those that can dive at great speeds (e.g. falcons), which retract their wings to reduce their aspect ratios. These birds have even higher cwl's than racing seaplanes (e.g. S6b), WWII fighters and the earliest jets (e.g. Meteor) . Only the fastest jets have higher cwls. The highest of all are the Starfighter, EE Lightning, B58 Hustler, F4 Phantom and SR71 Blackbird - but those are more or less flying bricks!

Don, Neat tip re preventing bleeding! Thanks.

I never use 5 minute epoxy, because it becomes unworkable too quickly for the speed at which I work!.

Great work! Looks as though it will have a really low wing loading.

I always fully charge my RX batteries before I go flying and I find that I can do a lot of flying before the loaded voltage comes down to the nominal voltage. So I would probably set an alarm to 4.8V for a 4.8V battery- but I've not tried this in practice.

>No the debate Don are you addressing this reply to me or someone else? Are you also BEB?

>It isn't really up for debate What are you referring to: the content of the debate or the the debate itself?

The energy density of batteries versus fuel is the biggest reason I don't fly electric model planes more than i.c. ones. I anticipate that my interest in electric planes will increase as the energy density of the batteries increases.

I have to disagree with BEB - I think this has been a good discussion of the pros and cons of i.c. and electric model engines (witness the great interest it has provoked) that has been neither tedious nor wandered far off topic. One of the disadvantages of i.c. engines versus electric is the oily mess they make, and some contributors to this discussion are now merely pointing out that with more modern oils and lower oil contents it's not such a bad issue as it was.

Over a fifteen year period up until a few years ago, I tried a lot of the standard anti-virus software packages from the awful Norton and criminal McHaffee to the dubious Russian Kapersky, all of which seemed to put malware onto one's machines and were quite difficult to get rid of. I eventually landed on Webroot, which I have now been using for about five years and which has performed with no problems or irritations

I don't think it would be too difficult to compile a table of "typical noise levels of Laser engines" at 7m (i.e. according to the BMFA 7m test). All you would have to do would be to ask for volunteers to bring their Laser-powered models up to your local flying field to be tested. You could insist on a few standards such as APC props. Maybe you could get several clubs involved. I think it would be very useful, because some clubs are pretty fussy about noise.

Erfolg, You will be glad to know that I am very interested in Electrical and Electronic Engineering and actually went to Leeds University to study that subject in 1969 (though I changed to Earth Sciences later because I wanted a more "outdoors" job). In the early 1960's I made single channel radio gear (TX and RX and Galloping Ghost) from scratch, etching printed circuit boards, and all the mechanical parts of the TX as well. For the transmitter joy sticks I used Woolworth screwdrivers with the handles rounded down. It is not that I don't like electrics, it is just that I prefer flying i.c. powered models - although I do have several electric ones. I also think that i.c. is still relevant today, especially as scale models are all of full-size aeroplanes that are powered by i.c engines. I have given my word to several people that I will move over fully to electric powered models the day that all the Rolls Royce Merlins in vintage Spitfires etc have been swopped out for big electric motors. Also, I fly in full size planes about forty times a year - and I am off to Arabia tomorrow in a typical modern airliner (787) - so i.c. engines are still relevant to me and quite a lot of other travellers. Remember too that the aeroplane owes its existence to the invention of the i.c.engine, so surely i.c. is somewhat relevant to our hobby.

"Why is there no I.C. RTF mass market?" Isn't this because the profit margins for the manufacturers and distributors are way higher on RTFs (plastics and foamies) than balsa and ply ARTFs? In America, the distributors are reducing their lines of ARTFs for that reason. And you can't hang an I.C. engine on a foamy too easily. So perhaps the relative increase in electrics is being driven partly by the supply side rather than the demand side.

Erfolg, I guarantee that a Laser V in your house (yes, in the living area of the house) will induce gasps of praise and admiration, at least from the male half of the species. By comparison, electric motors in the vicinity are likely to be more or less ignored, like unwanted wallflowers! BTW cupboards in the house are ideal places to store model planes, and after a bit, you never know, your wife may come to appreciate the pleasant faint aroma of glow fuel. (She may even take up the hobby.)

Electric RTF foamies may be a good way of "getting people into the hobby", but will it keep them in? I personally started aeromodelling in the late 1950's and 60's for the challenge of building the planes and then the challenge of flying them. It had nothing to do with the ease of building or flying. I am grateful for ARTF's for getting me back into the hobby when I didn't have enough time to build models, but now that I have retired I have gone back to building because, after putting many ARTFs together, that gets rather tedious. I worry more about the damage that RTF electrics are doing to the hobby than the demise of i.c. engines. Many people who buy "park flyers" take them out to a local park, without joining a club, and crash them or lose interest in them very quickly. It would be interesting to know what the average number of hours (or minutes) of flight time is on all the electric RTFs that have been sold. This particularly applies to camera-bearing drones with gyro stabilisation and GPS. I have one that I bought a year ago, and it's amassed a total of about half an hour of flying! It's wonderful technology, and if I was using it of commercial purposes I would love it. But flying it is pretty dull. To land it, you hit a switch and it flies back until it is overhead and than lands at one's feet. Miraculous, but about as interesting as turning off the TV with the remote!

Dave, Glow fuel is not a fossil fuel - it's comprised of methanol and nitromethane and some oil (which could be non-fossil).

Yes, here we go again, but with a provocative heading such as "Death of IC", I think it is deserved. It's great that we have all types of power plants in our hobby. Personally, I have a few electric planes but I find the ic ones more interesting and I find charging batteries more of a hassle (for very limited flying time) than filling tanks with glow fuel and cleaning models. I also find the articles in the magazines on electric ARTF and RTF foamies rather dull. I would be very surprised if 2S glow dies out completely - engines such as the OS46AX and 55AX are just too good in times of reliability and power to weight ratio for that to happen. I much prefer the sound of 4S glow, though. I haven't gone to petrol yet, mainly because I don't like the smell of petrol. I have belonged to five clubs and I have seen a slight tendency for a blind eye to be turned to the very raucous noise of large petrol powered planes (often because the people flying these are senior members of their clubs) and a disproportionate fuss being made over quieter glow engines If I was forced to fly electric planes only, that would seriously diminish my interest in the hobby. Vivat internum combustione!

Like so many things in aeromodelling (and most things), preparation is key. In the same vein as "measure twice (or three) times and cut once", it really pays to select the wood for the wing spars carefully. Someone who has strongly advocated that is Dave Platt in his really useful videos. It takes very little time to match the wood for spars, port and starboard, top and bottom by their straightness and bending behaviour. The same goes for the wood used for sheeting. Symmetry is everything, as is having a true building board and holding everything where it should be while the glue dries, whether you are using pins or magnets or weights. I favour weights, and back copies of RCME are perfect for weighing wings down, as long as the wing structure is jigged accurately.

For those interested in the discussion on chicken hopper tanks and how many to use with a Laser V, I have done some tests with my Laser 200V inverted on my testbench with one large upper tank (about 22 oz) and one very small lower tank (2 oz). I just managed to squeeze in two feed (clunk) lines into the small tank,in addition to the spill/drain line, the hopper fill line, and the air release line. (I used a Slec tank fitting on the top of the tank for that line.) My layout is exactly as described by Steve Dunn in the useful diagram he posted on 16th Dec, and it seems to work perfectly on the workbench. My only problem now is that the engine seems mighty loud at full power - I measured 86 dB at 7 metres. For these hopper tank tests I used an 18x6 Master Classic airscrew, but I am thinking of loading the engine a bit more with an 18x8 or 20x6 prop to reduce the tip speed. Anyway, I am now fitting the tanks to my Black Horse Turbo Beaver and I'm hoping that the engine will be considerably quieter once cowled and with different props. Jon, any comments on typical noise levels of Laser engines when fitted with the most suitable props, etc?

I think the decision to buy a 3D printer for aeromodelling probably depends on what you want to do. For a whole plane it may be worthwhile, but for odd parts here and there I can't see that it adds up. For small parts, such as fairings, etc, it makes more sense to upload the necessary files from your 3D drafting package to one of the online 3D printing companies. Then you have access (at a price) to vastly superior 3D parts made on top-end, state-of-the-art machines that cost hundreds of thousands of dollars. This is what I have done for the 1/5th scale Supermarine S6b that I am building. The 3D parts (from Shapeways in New York) look great and are very tough, but I hasten to add that the plane has not yet flown and it will be interesting to see how these parts, and their paint finish, stand up to the rigours of model flying and glow fuel. My main hesitation in buying a 3D printer now is that the technology is advancing so fast that almost anything one buys is bound to be obsolete the moment it has been bought! The technology is improving whilst the price is coming down.