Hasse
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Everything posted by Hasse
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Hi all, Just an update. I changed the fuel hoses from the main fuel switch and forward (under the cowling) and used 5/16 (suction) and 1/4 (pressure) - no problems. However, I got worried when I saw the condition of the original hoses (that came with the kit seven years ago). In particular the bit that runs outside beneath the floor from the fuel switch to the electric pump was in a very poor condition with cracks and was actually leaking. I suppose that the hoses in the new Savannah kits are better than what I got seven years ago but if not - don`t use them! -
Thanks for the comments! I will use the Gates fuel tubings as recommended and will stick to three dimensions (1/4", 5/16" and 3/8")(6, 8 and 10mm). I am not looking forward to the job exchanging all those fuel tubes. Removing all the sheets, all rivets, awkward positions, emptying all tanks from fuel and explosive gas. Would it be a good idea to ventilate the tanks with N2 or carbon dioxide, perhaps? Anybody who has done this and could give some rocommendation? Thanks Hans
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Hi everyone, It´s time for me to exchange all the rubber fuel tubings in my SavannahS, Rotax 912 (eight years since built). Four dimensions (6, 7, 8, 10 and 11 mm) were delivered with the kit and as some dimensions are difficult to find (particularly if you want a quality brand) I wonder if all dimensions are really needed. For instance, the 7 mm tube is used to connect the mechanic pump with the electric pump while the 6 mm tube connects the mechanic pump with the "spider". In other words, fuel to the mechanic pump is delivered via 7 mm tube and fuel from the mechanic pump via 6 mm tube. Is there a reason for this based on flow, pressure or what or can I use the same dimension to and from the mechanic pump? If there is a reason, would it be possible to keep the 6 mm and exchange the 7 mm to a 8 mm tube which is easier to find than the 7 mm tube? Also, the 11 mm tube is used for a few connections in the wings while all connections from the wings to the fuel reservoir are 10 mm (3/8") as well as the tube from the reservoir to the fuel valve. Perhaps I could use 3/8" tubes for the wing connctions instead of the 11 mm? Do you Think it would be possible to skip the 7 and 11 mm tubes and stick to the 6, 8 and 10 mm (1/4", 5/16" and 3/8")? Many thanks Hans
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Hi Capillatus, Thanks for the nice video. Where are you located? I've got a Savannah at Kjula (ESSU) and would very much like to visit as many places as possible in Sweden, and in particular those with reliable ice thickness on the lakes during winter.
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Hi Mark, Hmm, I see what you mean. Problem is that during flight testing (has to bee 50 hours to complete the personal flight manual - Swedish rules for experimentals) nobody can join me. So for another of 30 hours or so it will be only me, a couple of sandbags and the GoPro on board. Also, now it's autumn which means lousy flight weather until Winter. So I have to wait a bit longer with the final testing. I asume it's the oppposite in Australia./Hasse
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Hi 1Phils, Ok, so did it keep its attitude or became it softer after the bending?/Hasse
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Hi Mark, You are absolutely right. That's also what I found. I jumped inside and taxied around for a minute and after that both wheels pointed outwards. At present I always fly at MTOW (with two sand bags as a passenger) for testing reasons and that extra weight may also add, I suppose. Anyway, it's good to know that the main spring is probably not destroyed, only a bit too soft, in my opinion. Thanks all for your help - this is a great forum for discussion and support./Hasse
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Yes, well that's also what I thought. I found it quite soft. On the other hand, shouldn't all Savannah main springs have the same hardness? Anyway, I will see what happens after a couple of normal landings./Hasse
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Thanks you all for your help! However, I am not going to re-bend the main spring after all . When I tried to remove the spring I happened to place a jack on the spring in the centre under the U/C and lifted the aircraft in order to support it later with some trestles. Anyway, this pressure on the spring seemed to do the trick because the angles now seems completly ok with both weels pointing outwards as they did before. Apparently the spring has some kind of flex-point which should not be exceed but if this happens (within some limits I suppose) may be restored just by applying pressure in the centre and push it back. Does that make any sense? If this doesn't work, I will let you know/Hasse
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Thanks IBob, The picture and your drawing are great help when bending the main spring to the original angles. I hope you will be flying soon./Hasse
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Thanks Kyle, You wouldn't happen to know what angle I should aim at? I assume around 10 degrees.
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Dear friends, Has anyone removed and re-bent the Savannah main spring? If so, how did you do it? According to ICP this may be done twice without affecting the spring strength significantlly. I can't remember having done any really hard landings but either my memory is going bad(mad) or the main spring is too soft for my hands. Still, there are a lot of talk about the front wheel suspension but I couldn't find any threads in this forum where people have complained about the main spring. Anyway, rumour says that ICP has a new and stronger version of the main spring./Hans
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Hi Peter This is good news but surprises me somewhat. Considering the gravel and the small wheels I never thought the Savannah would move forward unless full throttle. Also, when landing, if I understand you right, you can keep the nose wheel off the ground until about 15 kts? Must try this - without gravel/Hasse
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Great feeling, I can imagine! Quite rough surface and not very long but obviously sufficient also for a take-off. How much did you need?
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Yes "Head in the cloud" there are many more test that can be done but not by me. I am sufficiently convinced by my test results and will change from car petrol and start using, as often I can, 91/96 aircraft fuel which is ready accessible in Sweden. Btw, neither ethanol nor iso-propanol gave any cracks in my tests.
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Ok rankamateur and Heads in the cloud, I'm not familiar with the chemico/physical basis of the development of cracks in the Lexan, polycarbonate. However, let's say that you are right (which I doubt) and that it all depends on the rate of evaporation. If so, than Mogas (with aromatics)evaporates at such a rate that it creates cracks while aviation fuel 91/96 (without aromatics) does not. This is not very likely as the two fuels have approximately the same vapour pressure. If you distribute small aliquots of the two fuels over a surface you will find that they evaporate at approximately the same rate. If the cracks in lexan is due to evaporation this cannot be the whole truth. There has to be some sort of initial dearrangement of the polycarbonate (caused by the aromatics) that is especially pronounced in areas under stress prior to the temperature effect caused by evaporation. Personally, I wouldn't be surprised if mogas would induce cracks without any evaporation. Something to test? Anyway, here are the links to my small tests. Please excuse my English and poor directing (not all Swedes are related to Ingmar Bergman). You should be able to open the links by coping to Google./Hasse
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Sorry, but I can't leave this "crack business" to rest. Where I live, I have several pilot friends who claim to have spillt lots of standard aircraft petrol on lexan doors and windows with no or only little signs of cracks. Why the difference from my experience? The only difference as I see it is that they have to use the lead free aircraft fuel (called 91/96 here in Sweden) that lack aromatics like benzene and toluene, which in contrast are always present in car petrol. Therefore, I made this small test comparing the effect of 91/96 aircraft fuel and car petrol (mogas) on Lexan (bent with rough edges). I also added a piece of Lexan where the edges were protected by polyurethane tape (same as propeller tape). The results was pretty obvious - fuel without aromatics does not crack the Lexan. Also, polyurethane tape appears to give a considerable protection to the effect of mogas. I will show the video as soon as I learn how to./Hasse
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Hi Nev, Ignition OFF? There won't be any windmilling propeller on a Rotax with gearbox, right? So, at landing, either full throttle or ignition OFF with a silent engine and immobile propeller meaning you need to engage the starter to wake up the engine. Interesting situation! Hasse
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Agree, there is essentially no risk that the rods between the manifold axle and the carburators will break. However, as I also have changed the original throttle control sticks to push-pull friction lock controls (AS, A-800) there may be a "weak" spot. This would be the cable end "B" nut which connects the friction control to the manifold axle and the rods. If this breaks or loosens I have to reach over and try to control from the passenger seat. If booth cable ends breaks up then it would be nice to have weak springs that opens the throttles. There are perhaps many more options. Hasse
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Hej Rankamateur, Perhaps, but the standard set up with flexible wires obviously needs the force from springs to pull the wires to open the throttle. I would imagine that the extent of this force depends on the friction in the wire cables. Still, the weaker springs that Rick mentioned have about half the force of the originals so that might be sufficient. Worth testing!
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Great! Will test both without and with weaker springs. Btw. You and this forum are invaluable sources of information and assistance. Many thanks. Hasse
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Hi again Rick! I've just installed and tested your recommended throttle conversion and it works very well. Thanks for the suggestion! The only minor remaining obstacle is that I still find the original Rotax carburator tension springs too strong for the purpose and make it unnecessary hard to fine-adjust the throttle. Do you know if anyone has tried to install weaker carburator springs? Hasse
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Great! Many thanks Rick, I found the parts and have made the order.
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Hej Rick, I like your throttle "solution" and will try it but there are two things that I can't figure out. First, where did you find the device that you used to anchor the friction cable and pass it through the fire wall? Secondly, where did you find the neat wire stop that you used to anchor the friction cable end to the main axle arm? Are these parts to be found commercialy or did you made them yourself? Any hint is appreciated because the original ICP throttle control does not make me happy.
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Yes "Head in the Clouds", Agree, polycarbonate is the obvious choice even with petrol spilled all over the screen - provided the sheet is flat and unstressed. Unfortunately, windows and doors in the Savannah are bent and under stress and do not love petrol.
