IBob

Hi Kurt, really interesting to read of your control mods and see your progress! I'm most interested in your Arduino work: I do a bit myself. Credit where it's due: my fuel valve setup is a direct copy of Mark Kyle's setup on his original XL, and I referenced his build thread here a great deal during my own build. Also, and as Mark mentions, I fitted a flashing LED instead of the bulb supplied for the low fuel indication. I then fitted a second one in parallel on the pilot's side (the standard indicator goes on the RH side of the panel). The flashing LEDs were sourced from RS, the fuel manifold and valves we source from China, though you may have more economical sources where you are. Keep the pics coming: it's great to see another aircraft coming together.

Yep, a couple of things struck me. The first was that, while Juan Browne is an excellent and knowledgeable commentator, in this case he was commenting on something that he clearly has little practical experience of. The second was the amount of time they spent stacking that aircraft: a full 30seconds and it may have gone on longer without the stall, the way they were mucking around. During which time the aircraft is burning off height and flying on beyond the spot. Given that the thing has handles and steps, it should be easily possible to stack and leave in half that time.

It does sound like the Camloc would be your better option. That's what I have on my oil inspection hatch, which is opened every preflight. I think they are better suited to that sort of constant use.

Give us a clearer idea of what you are trying to do Spacesailor. My aircraftt has Dzus for the fg cowlings (higher load, greater weight) and camlocs for oil inspection and belly hatches. Different fasteners will be more appropriate in different applications. In all cases there will be lookup tables identifying the sizes and how they are measured. It's just you sometimes have to do your own homework finding the appropriate table. And you have to know how they are measured, or you're just guessing. I would guess Aircraft Spruce only take orders for part numbers to avoid arguments with folk who guessed, then didn't get what they wanted. Camloc info is here: scroll to the bottom and it says how to measure for them: https://www.aircraftspruce.com/catalog/hapages/camloc4002.php It doesn't look as if they carry the shortest size. If it helps, the shortest (slotted head, undercut) Dzus is the AJ3-25 for 3/16" diameter or AJ4-25 for 1/4" diamrter. (So the first part of the number is diameter in 16ths and the last part is the length in decimal....gotta love this stuff!) They have a length of .25 or 1/4". If they are still too long (or if you have to buy the next size up which is AJ3-30 or AJ4-30) all you do is pack and/or rework the spring they get hold of.

Blueadventures, my cowl is inside and I would do the same again. The purists would say it is less streamlined, but this is not a streamlined aircraft and I can't see the overlap making any difference. I also like the idea that my cowling is more likely to stay with the aircraft, tucked in as it is......) My understanding is that it used to be a struggle to fit some cowls this way, but for me it went very easily. Maybe this is a feature of the XL and S, probably also it is due to the corrugated steel hoses that allow very tight smooth bends without flattening.

PS for anyone building: due to variations in cowl thickness, some adjustment of the individual fasteners will probably be required. I did this by reworking (okay, bending) the springs, and in some cases by packing under the spring where it is attached to the inner cowl. As with all cowl fitting, this really needs to be done before the paint.

It's also challenging for those of us with more than the usual pair of thumbs, Nev.....)

Here is the Aircraft Spruce page that spells out the dimensions: https://www.aircraftspruce.com/catalog/hapages/dzus.php Note they are measured from the head to the spring bar they attach to. That's the -40 and -45 of the number, which are 400 and 450thou respectively.

Savannah supply homegrown aluminium fasteners that can bind and spread. I replaced all mine with steel Dzus from Aircraft Spruce: Model Cat # Quantity 121J-540-Z3C AJ5-40 13 121J-545-Z3C AJ5-45 3 That includes a couple of spares, though I have learnt to be really careful taking them out when on grass.

Plus one for the Lightspeed Zulus here. I've always struggled to hear over noise, I find them very good. And surprisingly good even if you don't turn on the ANR (don't ask.........).

You're welcome, Kurt. During my build, I benefited hugely from the posts of others on this site. My aim was to add to that by posting some of my own. Further fuel system comments after 2 years of flying. In no particular order: I have had no fuel leaks. I am very happy with the fuel valve arrangement (copied from Mark Kyle's first build) which I firmly believe is the best option when using 4 tanks. This allows flexible management of all 4 tanks (typically I would take off and climb, descend and land on inboard tanks, switching to outboard for cruising). It allows simple periodic testing of the low fuel switch in the collector tank, which cannot otherwise be tested without draining all tanks. (There is a test button on the panel, but this tests only the indicator, not the switch, and the switch can fail.) And it allows the outboard tanks, which are less often used, to be flown to exhaustion in cruise. If building again, I would pass the various tubes to the face of the inboards tanks through larger grommets and holes in the ribs, since the tanks may shift and swell some with use: that is, I would allow more clearance round tubes where they pass through the rib. The newer kits now have inspection hatches allowing access to the tank fittings. I think this is an excellent idea. I fastened my under-tank panels with rivnuts, but fitting inspection hatches is a far more workable solution. I had uneven feed from L and R tanks. Apparently most aircraft have this, and it is very difficult to eliminate completely. In my case, more fuel was invariably taken from the RH. I was able to greatly improve this by removing all undulations from the LH lines where they passed across the rear of the cockpit. The lines were hose at this point, and I now have them held straight by tying them to a length of aluminium L section with cable ties. (This is all tucked away inside the simple shelf I made to carry the lines across.) This has effectively removed high spots where air can sit, impeding fuel flow. A final improvement I may make, though not essential, is underwing breathers of solid pipe, rather than the plastic lines I currently have. These work well enough, but do not sit straight, so despite trying to trim them evenly they will tend to give slightly different tank pressures. My thought is to have aluminium tube down through the wing, with the plastic pipe on top allowing removal of the fuel caps. I would have the underwing part trimmed at approx 45degrees to the airflow, like the plastic ones. At one stage I did experiment with forward facing breathers, but abandoned that very quickly as it resulted in excessive tank pressures and a huge amount of crossfeeding. All the best with the build, Kurt. Do post some pics as you go, we all enjoy seeing an aircraft coming together.

Onetrack, I'm pretty sure the issue of gusts etc has already been dealt with in part of the wider discussion this caused. However, on reflection, I'm with Facthunter on the treadmill issue: not because I think the idea of using a treadmill is invalid, but because what we see there is a momentary snapshot quite probably affected the momentum of the prop. What we would need to see (for the treadmill experiment to be convincing) is a very long treadmill and the vehicle continuing to make it's way along it after the initial burst introduced by the operator holding it still.

Weird that folk can accept a vehicle travelling crosswind and on various headings at well over the windspeed, but they can't consider a mechanism for doing that in one particular direction......)

Maybe part of the confusion is around what is driving what. As I see it, the wind is pushing the car (downwind). If the car is moving, the wheels are turning. If the wheels are turning, this causes the prop to turn, since the two are linked. And the prop is pitched to blow backwards , into the wind. It's the wheels that are driving the prop, not the other way round. And if the car is travelling downwind at wind speed, the prop is turning, pushing back against that wind, so causing the car to go faster than wind speed.

BTW and if anyone is interested, the performance of evac tube solar water heating is outrageous: I have the smallest 20 tube system and it provides all our hot water for about 9months of the year, and some of it for the other 3 months. The operating principals are totally different to the old flat plate technology. This thing is actually a heat pump that works even on overcast days. Heading into summer, I am (again) looking at ways to dump the excess heat. Ours is a low pressure system. My only reservation in a high pressure system would be the long term durability of the header that takes the tubes.

Yep, I have an evac tube solar hot water system, with the collector some distance from the hot water tank. Took a fair bit of tinkering to get it settled down. The supplier kept insisting the (multispeed) circulation pump be turned up due to the distance, in the end I turned it down to minimise cavitation as the water temp rises. It still grumbles sometimes, but it works, and has been for some years now.

Turboplanner, I live in a 1920s bungalow, with a header tank lifted as high as it will go in the roof space (not very high, about 1.5m at the base, due to shallow roof). The outfeed goes horizontal across the width of the ceiling space, then down a cavity to under the floor, where it is then split out and piped to the various taps and hot water cylinder. The header tank is supplied by a pump. If we allow this system to drain during a power cut, it will not then prime itself once we have water back in the header tank: nothing will come out of any of the taps, including the lowest, which are bath taps approx 700mm off the floor. To get the system going again, I go out to a tap I installed which is almost on the ground and connected to the lowest part of the system. Turning this on results in about a minute of gurgling and spitting, then a small amount of water, then full stream. On the odd occasions when house-sitters have been told what that tap is for, they listen to this with an expression of benign disbelief. And even though I figured out why this happens, it's still oddly counter intuitive to have a tank in a roof and taps down below, but no water coming out... I found this situation instructive when it came to building my aircraft: I went to some lengths to remove any undulations in the fuel pipework.

It's certainly a curly one, Bruce, and if we can believe the story, the physics prof lost $10,000 and I would suggest part of his reputation because he couldn't see it. While some of the principals are different, I found the wheely thing at about 1330 on the YouTube recording quite useful: it shows a free running wheeled object being driven forward by something pushing on it, but travelling forward faster than what is pushing it. In a sense that is what the wind car is doing: being pushed by the wind, which turns the wheels, a certain amount of that turning energy then being used to push back against the wind.

Bruce, if the wind dropped to zero, the various frictions of the wheels etc would cause the vehicle to slow and stop. Exactly as it does with any other vehicle. I can see where this may look like and attempt at a perpetual motion machine, but it's not. It would only be that if the thrust developed by the prop was greater than the rolling energy required to drive the prop. So it can't work in nil wind, but with a constant wind delivering energy to the system (by pushing it along), very careful gearing and avoidance of friction enable the rolling wheels to also turn the prop. I would suggest there is a narrow envelope where this works, or we would indeed have something that accelerates indefinitely!

Bruce. with no wind the only force acting on the thing would be gravity (okay, and equal air pressure all round) and no resulting movement on flat ground.

We just had yet another Americas Cup, with all the contenders sailing faster than the speed of the wind. Granted this was not downwind, and granted the mechanics of what is going on is different and initially counterintuitive, but I can see no reason to reject it out of hand just because we can't initially see how it works.

I don't see why not: in both cases the air is moving relative to the surface. If you think about it, the planet we live on is one enormous treadmill moving under the atmosphere around it?

I'm amazed at how very polite and civilised this conversation is. And especially in light of the fact that a slice of the aviation fraternity still measure their masculinity by the position of their third wheel...............)

Looking really good there! Just PM'd you.....

Marty_d who is building a 701 but using some savannah parts including wiring, raised the same question here on 11 August: https://www.recreationalflying.com/topic/28196-marty-ds-ch-701-build-log/?do=findComment&comment=512650&_rid=6547 It's not clear what the other wires are intended for. But it would be nice to know!