Firstly apologies for my last post which was a bit sketchy on the details. I was very tired that night and really should have waited until the following morning to write that post.
This week I've cracked on with fitting the wheel spats. No big dramas there - the plate on the inboard side of the wheel that aligns the holes (and nut plates in my case) has to be in exactly the right position. It had moved under transit to the paint shop and back so gave me a little bit of a headache while I tried to figure out why the spats did not fit like they used to! Also the front of the plates where bent out a little bit - again in transit to the paint shop - so I had to straighten them back again.
Next up was performing a fuel flow test. The LAA insist upon this even though we have a fuel injected engine. Good to do anyway for peace of mind that everything works as it should and the flow rates are the same, which they were in my case. See the maths below which shows that the fuel pumps deliver 136.36 litres per hour! More than enough for the max consumption of the UL 260iSA which is 27 litres per hour. The LAA want to see 125% of max flow, we have 500% - more than enough.
Those of you worried about me putting the pipe wrap on one of my exhausts can now sleep easy. I have removed it. After reading on Kitplanes about cowling heat management, Larry Vetterman (the Godfather of light aircraft exhausts) said pipe wraps are a bad idea because they increase the temperature of the metal to an unacceptable level and can even damage the stainless steel. I've removed the thin Fibrefrax and replaced it with thick Fibrefrax - 1/8 inch in the area closest to the exhaust. Fingers crossed it is okay and doesn't melt my newly painted cowl!
Next up was cleaning the inside of the fuel tanks. Ewwww what a stinky messy job this was. Petrol is nasty stuff! There was a heap of crap inside the tanks, some of it was from when I was fitting the fuel caps but there was also a lot of primer that got in there from the paint shop. I made up a cleaning device with an old toothbrush inserted into a piece of fuel hose and taped in place. This did the trick nicely and I was able to scrub away all the primer. A flush out with fresh fuel and things are better. I will not fly the aircraft until the pre-filters are replaced though as there will no doubt still be some crap in the system that will find it's way to these filters that are just before the fuel pumps.
I finally got around to doing the Chemseal (Proseal) job on the fuel sender/tank plates too. Ultra messy stuff this, kind of impossible to make a neat job with it. Lucky no one will see this as it's on the inside of the tanks.
Onto the ailerons...
I was struggling a bit to get the correct range of movement with one aileron and finally decided I should phone Pete. He said "Along with the retractable gear the ailerons are the worst job on the whole plane". This made me feel better. He said you could spend a week trying to get these right and still never get there. He's tried all sorts of fixes over the years but at the end of the day you have to accept the range of movement you get when both ailerons are connected as one will limit the other. I've managed to get mine within the ranges so that's good. I had to grind a fair bit off the bottom of one weight to get the clearance.
The control 'stop' by the way is the counterweight hitting the wing skin inside! This is altogether wrong and a proper control stop should be fitted. I noted that the French Twister had a mod to include a control stop on the bottom of the stick in the cockpit and this is a good idea.
The manual is wrong with the maths on the balancing section too. See below screenshots. They have copied the text from the flap section and not updated the Fulcrum distance so the maths is wrong. They say an answer of 7 when it is actually 21.54 given their figures. The distance from the Fulcrum on the ailerons is 12cm and when that figure is used the 7 comes out correct. Confusing or what!
Either way there is no way the aileron will be within the weight they state also. 1.75 to 2.2 kg. Mine was over this before paint!
The most important thing that has to happen is that the counterweight must be heavy enough so that the aileron is 'nose heavy'. The measurements I got in the end were as follows.
Port aileron: Scale reading of 96 grams (0.096kg). So 0.096 x 9.81 x 12 = 11.3
Starboard aileron: Scale reading of 75 grams (0.075kg). So 0.075 x 9.81 x 12 = 8.8
So both are well within the limit of 25 to 5.
The weights suggested in the manual for the counterweights are really out of range massively as I ended up adding about 50% more lead weight to get the range correct. Lucky I had some left over from the flap counterweights - which are not needed anymore. I bonded these in using flock then the next day followed up with a layer of Carbon over them and part of the existing weight to make it secure.
Tomorrow G-FUUN will make it's way out to the airfield to play with the other planes. I have a feeling it's going to be a long day with picking up the trailer I am hiring and making at least 2 runs to the airfield, not to mention the loading and unloading. A beer will be in order on Friday night for sure!
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| Spats on. They are probably the only element aesthetically that I don't like on the Twister. Maybe one day I will build my own. |
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| Spats don't look bad from the side - it's just the front view that I don't like. |
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| All set up for the fuel flow test. 5 Litre measuring jug on the return line. |
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| iPhone stopwatch is good for measuring accurately. |
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| 500% of max consumption - I'd say that's good enough! |
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| Gizmo for cleaning out the fuel tanks. |
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| Crap that was inside the tanks. |
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| Pipe wrap removed and the closest area of the cowl replaced with thick Fibrefrax. |
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| Chemseal on the inside of the fuel senders. |
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| Messy stuff! |
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| Measuring the counterweight on the scales. |
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| Amount shown here is not enough! I had to add more and about 50% of original weight on one aileron. |
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| Aileron maths - wrong! |
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| Taken from the flap text I think - without changing the Fulcrum distance figure - as this maths does make sense. Although spot the mistake - it still says a scale reading of 0.06kg then has 0.14kg in the equation. |
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