Birgir
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Hi I have been thinking about LED-lights and an easy way to implement navigation lights into some of my models. The reason I’m planning this is not only for decorative purpose but also to make it easier for me to be certain about the direction of the model in the air. It has happened, when the model is far away, that I’m not sure for few seconds and that’s not nice Browsing the net I notice that many are advising to put a resistor with every LED and connecting to the receiver battery through the receiver. My plan on the other hand, is to use a 3 volt button-battery to power the LED with no connections to the receiver battery. I’m planning to have a battery slot somewhere in an accessible place on the model where I can slip a button battery in, to turn on the lights. My questions are: If I’m using a 3 volt battery for a 3 volt (approx.) LED do I need a resistor? Is it ok to connect a few LEDs parallel to one battery, for example a CR2032 3V? Comments and ideas are welcomed. Birgir
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I‘ve been thinking (yes, it does happen) about prop types and sizes. Earlier in this thread there was an informative discussion about prop sizes. After some testing with a very primitive testing method, rubber band and a ruler, I came to the conclusion that a 10*4 was giving the most pull and decided to stick to that prop size at least while solving other problems (CoG, weight and better wheels) I understand that a higher pitch gives more speed and more diameter gives more thrust. So if I want to keep load on the motor constant, I can get more thrust with more diameter and smaller pitch, but that would, in theory, give lower speed. For my Bleriot and SC30FS it appeared in my rubber band test that 10*4 would work best. That was actually suggested to me much earlier, i.e. aiming for thrust rather than speed. (Thanks Jon) I have been using nylon props, Robbe Dynamic, for all my testing and flying because they don’t brake easily and can survive a nose over or two. But from aesthetic point of view a wooden prop would look much better on a Bleriot and it has also been suggested that a wooden prop would max performance. So now to the actual question. If I go from Robbe Dynamic nylon prop to Turnigy Type A Beech Wood Propeller, can I use the same diameter and pitch? Jon Harper has pointed out that those A type props run really fast and therefore I might use 11*5. Based on my limited experience and knowledge I would think that 11*5 would put more load on the motor demanding more thrust and speed than 10*4, especially if it spins faster due to thinner blades. I would welcome any explanation, comments, suggestions and tips about the difference between using wooden and a nylon propeller. B.
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Following Donald’s suggestion, I switched 100 gr of lead with 3 * 25 gr and took off. Everything went ok but it didn’t seem to make much difference. So, I landed, removed 25 gr more and took off again. Everything still ok, a little change for the better, not as much elevator needed to maintain constant height. Next decision: remove another 25 gr. Now, my courage was increasing and I had a new idea. How about different style of landing. Until now I have always landed on half a throttle, flying the plane in, aiming for a smooth landing. What about having the motor idling and gliding in for landing? Well in just a few second I realized that Bleriot XI is no glider. Under cambered short and wide wings are not at all similar to gliders wing. The model came down more like an elevator than a plane. When landed, I realized that somewhere before, I had seen a picture of similar landing. Talking about scale Luis Bleriot’s first landing in UK was probably very similar to mine. Only minor damage and already fixed, further adjusting of CG must wait another day. B
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Thanks Donald But I‘m a little confused. When you say “too far aft” do you mean “too far forward”? I will take 25 gr. out at a time. B
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Today we had yet another calm day in Iceland, - what is the world coming to. I did some more practice on my Bleriot and now I have two tasks at hand. The first one is fine tuning of my SC30FS. When I run it full throttle for some time it tends to take a brake and stops delivering full power for five to ten seconds. If I relax on the throttle it picks up again. I’ve tried to lean the mixture, quarter of a turn clockwise, but that increases the problem. If I make the mixture richer, turning counter clockwise I’m not getting as much power. Does anyone have experience of this? Could this be something that disappears with a little more running in? The second task is trimming. As I´m getting better at controlling the model in the air I now have started to trim for levelled flight. It looks like the model only has one speed, full throttle, and needs 5 degr. of up-elevator to keep constant height. Considering that the elevator area of the split stabilizer is quite big, (68 sq.in.) this is considerable amount of up-trim. There are probably two main factors to take into account. The first one is the down thrust of the motor. I haven’t been able to test this properly but it feels like the model slows its speed and loses height very rapidly when the throttle is pulled back, not pulling up as I would expect if the down thrust would be too much. It is as per D. Boddingtons plan. The second factor is the Centre of Gravity. At present I have got 600 gr of lead up front and the CoG is about 12 cm from the LE. On D. Boddingtons plan the mark is about 10 cm from the LE. Would it be right to presume from the flight experience that the ballast is still a bit too much and would be ok to move the CoG one cm further back or so? My intentions now are to remove 50 or 100 gr of lead and have a try. Does that sound sensible? Any thoughts, comments and ideas are welcomed! B. Edited By Birgir on 16/10/2016 18:45:35
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Hi everyone Today there is a fairly calm weather in Iceland, about 5 m/s, so I decided to practice a little more with my Bleriot Better tuned engine and also more running time has increased the power a bit but it still is very scale like. I have also put neoprene tires on the wheels – thanks for the tip David. The wind was a bit swift and the model was swept side to side. The take-off went very well, I have taken PatMcs advice to mix the left stick 30% to the right rudder stick and it works well. When in air the rudder and the split elevator do have a very good control over the model. Even when a sudden side gust almost rolled the model 45 deg. full rudder could level it off and for a short time it looked like the model was flying sideways, at least compared to the ground. I hope there will be more opportunities to practice later this autumn – this is very much fun even though the wind is about the limit the model and I can handle. B.
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Hi I ‘m still doing some exercise and learning to control the Bleriot. I’ve realized that in the first tries one of my mistakes was to use the elevator to keep the fuselage wheel on the ground. My thought was that keeping the fuselage wheel on the ground would help the control on ground and at the same time ensure that the model would not nose over. I was also worried about the tail being set too high so the take-off incidence of the wing would not be enough. I have now learned that it is better to relax on the elevator, keeping it neutral on the runway. The model soon lifts the tail getting into the correct fuselage datum line (I think). There is no danger of nose-over and it is much easier to get up speed. When suitable speed is acquired a small pull on the elevator stick gets it airborne. When in the air it is very important to keep the model straight into the wind using the rudder against the direction the model tends to go to. If not, it will drop a wing and go back to the repairing table. This is where I am at the moment. No major damage, just small fixing here and there. Any comments and advice are very welcomed B.
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Well, it still felt at least a bit stressful Actually I flew two flights. The first flight I left Luis on the ground (56 gr.) but added 100 gr of lead up front, having total of 700 gr. ballast. The power was very marginal and it felt more of a problem to keep the nose up rather than being tail heavy. So the next flight I skipped the extra 100 gr and put Luis in again (about 2630 gr total, I think). I also noticed that the elevators seemed to have moved on their axes. I corrected that, tightened the screws holding the middle and took off again. That is the flight in the video. After not so graceful landing I realized that the elevators had moved again and where not in line with each other. The aluminium pipe is not glued well enough in the elevators and can be moved. There were just a minor damage to two of the balsa pieces in the side of the fuselage. The lesson learned is. a. CoG about 12 cm from the LE looks ok at present b. The power is marginal but ok with 10x4 prop c. The split elevator does its job well, but needs fixing d. This was great fun! Birgir
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At last, at last – the first flight of my Bleriot tonight! Birgir
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Congratulations Dave!!! This is very interesting to hear. I’ve not been able to have spare time and calm weather meet yet but this news makes me very restless. Hopefully I can find a time on a calm August evening soon. Thanks for the description, it will help me to build courage for my first takeoff. B.
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Good to hear that your Bleriot is back on its feet again, David. It didn’t take you long to get it fixed. Lost 800 gr of weight, where is the CoG now? I fly mode 2 and if there is no aileron I have elevator and rudder on right. My first plane where three channel Kiel Kraft Mini Super with that setup, later I added aileron. **LINK** What size prop are you using? B.
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David, I think you have come up with a very solid plan and I look forward to hear about the result. I will try to learn from you and have decided to do the following Skip the extra 200 gr leaving the CoG at 33% Skip the on-board tachometer Leave Luis on the ground for the initial flight. This will probably loose about 250 gr of weight. By the way, in what kind of stores can you expect to find neoprene cord, what is it used for normally? I will leave for Glasgow tomorrow morning so more tests must wait until next week. B.
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Congratulations on the prizes David. You say 2 prizes, in which categories where those prizes? Sorry about your mishap but remember Luis didn’t succeed in his first try either. Thanks for the detailed descriptions it helps me a lot to prepare for the first take-off – and the first setback probably too. As you say it seem to have no major damage and I’m sure you can find a way to put the longerons together again without too much gain in weight. Am I understanding you correctly when you say “at least 30% back” you mean 30% of the cord of the wing, i.e. 30% of 34 cm that is 10 cm, or more. More being more tail heavy?. (Bear with me, English is not my first language) As you can read in my earlier posts here, I’ve added 200 gr extra to the front to get the CoG point from about 11 cm to about 10 cm back from the leading edge of the wing making the model 2950gr (A bit porky ) Maybe that is not wise after all. After looking at the pictures in you album it looks to me as the ballast is at the top of the “engine room”. Could it be better to lower it as much as you can to make the model more stable left-right? Did you have any time to experience if the wing warping system is doing its job? PS. Thanks Keith, but the wheels are made from foam band and are not really inflated. But probably a little too soft. The making of the spoked wheels is explained (in Icelandic) at : **LINK** PPS: „An expert is a person who has made all the mistakes that can be made“ - Niels Bohr B.
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Well, to be on the safe side for the CoG I added extra 200 gr of lead up front making it total of 800 gr. That included the total weight of the model is 2,950 gr. With the right prop and a hard surface, I'm still pretty convinced that I can get it airborne. B.
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Just for your amusement I put together a 5 min video of my first, failed flight attempt - enjoy!
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Thanks Jon I´ll bear that in mind. The good news is that the municipality has just finished building a cycle-path next to our airfield and it looks good enough to be used as extra runway for us. I might try that on the next calm day B. Edited By Birgir on 02/07/2016 17:58:10
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Dear friends I agree that wooden prop will be more scale like on a Bleriot so I tried to order the Zinger props that Jon pointed out to me. But Brian at Elite Models tells me that the production has stopped and they are out of stock. So I‘ve ordered a Turnigy Type A Beech Wood Propeller from Hobby King. **LINK** They look similar to me. Do you think that those props are suitable? I‘ve ordered 9x5 and 10x4. B.
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Posted by David Germany on 28/06/2016 21:10:06: We have our club Model Of The Year competition this coming Sunday and I was hoping to enter the Bleriot, only problem is that a condition of entry is that the model has flown previously or flies on the day. We'll have to wait and see. David How is the outlook – will you be able to enter the competition on Sunday? B
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Exactly, - and that is the reason for onboard tachometer ☺
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Thank you all for this discussion, it is very informative for me at least. The props I have been using are all robbe, dynamic, I have now tested five different props. 9*4, 9*5, 9*6 and this morning 10*4 and 10*5. Using my primitive rubber band, stationary, bench testing the 9*5 and 10*4 give the best result. The 9*4 went up to 12.000 rpm and is probably indicating that it is not delivering the power transmission intended. The 10*5 did 9,500 rpm and the 10*4 just over 10,000 rpm, stretching the rubber band a little more than the 9*5 did at 11,000. I now have a „on board tachometer“ and look forward to be able to have some max rev reading after the first flights so I can compare stationary and in flight rpm. Although I find these experiments and testing quite fun and at the same time helping me to understand the complex matter of prop sizes and pitch I think that probably Donald Fry is right. The main problem is the airfield. We have been cutting it very close and not putting any fertilizer in, so now we have the problem of soft moss taking over the grass. I believe that from a proper airfield I could get the model up to suitable take off speed without a problem. B.
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Thanks for the info. So, if I would use the fishing scale method to test for the amount of force needed to get the model moving on the grass field, subtracting it from the static thrust, converting it to Newton I could calculate the speed of the model on the runway in 10 sec. (s*N)/kg = m/s This should work in theory but the fishing scale method is far to crude for this to have any value in reality - I think. Is this logic correct? B.
