Simon Clark

All servos and pushrods / control surfaces act as a closed loop control circuit and any control system can go unstable under certain circumstances if the gains are too high and there is not enough damping. This is a slightly simplistic way of looking at it and the reality and associated maths is very complicated. It is possible that the mass of your rudder coupled with the mechanical throws that you have are hitting a resonance point and causing control instability. By gently touching the pushrod, you are introducing a small amount of damping which takes it away from the unstable point. Some servos will suffer more than others and with tolerances even two examples of nominally the same type may react very differently. It is safest just to swap the servo out for a different and better type but you could try changing the mechanics of your system a little by moving the pushrod onto a different hole on the control horn or servo arm - yes this will change the overall rates but to a certain extent you can compensate by using servo end point adjustment and rates etc. Good luck Simon

Hi, 8BA is just a little larger than 2mm but might be OK. You can get brass hex head bolts and nuts from MACC Models: https://maccmodels.co.uk/shop/8ba-x-1-2-hexagon-brass-pack-of-10-2/ https://maccmodels.co.uk/shop/8ba-brass-nuts-2/ They do other options as well Good luck Simon

I like the idea of Super Phatic and have heard some good thigs about it - just a simple question: do you just wick the glue with the sheets already pushed together like you would for cyano or do you open up the joint and apply the glue in the same way as for normal aliphatic. I assume it is best to wick it in but I have never used this stuff! Thanks Simon

https://bmfa.org/laurie-peake-1953-2021 Probably not what you wanted to find out. Simon

Thanks for all the replies - it sounds like I have got the right method but I need to be a bit more careful / skilled! Simon

I apologise if this has been covered before or is too basic a question but: What is the best way to glue balsa sheets together for wing skinning etc.? I usually start by taping the sheets together on a flat surface then open up the join, add some aliphatic and put back down on the flat surface with a few weights. It works OK but I always end up with a very slight mismatch in angles, a glue line that is difficult to sand out etc. Does anyone have a fool proof method that gets good consistent results? Thanks Simon

I agree that the RX should be OK if the pin block area of the PCB is checked and there is no visible damage or solder splats etc. However, be very careful with the ESC. One very likely failure mode will result in the ESC BEC outputting the full supply voltage. If this has happened and connect up with say, a 3S pack, then you will probably blow your RX and all servos attached to it. If you want to check the ESC, then try first with your 2S LiFe as the main supply and measure the voltage being supplied to the RX. If it is anything other than the expected 5V then the ESC is toast and should be thrown away. It is also possible that he BEC output will have shorted out, so when you connect your battery, be ready to disconnect immediately if anything gets hot or doesn't work as expected. Good luck Simon

Originally Spektrum servos were made by JR. The DS821 is definitely a JR built unit. When Spektrum went away from JR, they kept the original JR spline design. You can still get JR arms from many different places as has already been said. Simon

I have a degree in mechanical engineering and started off working as a mechanical development engineer in aerospace. Pretty soon, I realised that I wanted to understand electronics so I read Horowitz and Hill from cover to cover. After that, I ended up working mainly as an electronics engineer. A brilliant book, that makes sense of it all! Simon

I finally got round to finishing off my electric Tracer. I have flown it with the following setup and it is absolutely brilliant: Motor: Overlander 3542/05 (1250KV) Prop: CAM folding 9.5 x 5 ESC: Overlander 60A Battery: 4S 2200mAh, 45C I used this prop to make sure that hand launching was easy at the possible expense of top speed. Although the speed is probably a little bit down on the i.c. version in full race spec, it is not that far short and a real adrenaline buzz. To launch you just hold it in one hand, apply full power, hold with nose up a few degrees and let go. I have made a cut-out in the wing to allow the battery to be put in without removing the wing and this needs it to be reinforced with ply spars. The whole wing and tail are covered with lightweight glass cloth put on with epoxy. I have built it with no side or downthrust but it does climb under power so would have benefitted from a little downthrust. I have got round this with a simple throttle to elevator mix (although I haven't got it right yet). A couple of pictures are attached. Give it a go! Simon

I have no experience with this particular motor, and the info is limited, but might be worth looking at or at least giving Robotbirds a call to see what else they might have https://www.robotbirds.co.uk/mt2808-660kv-ccw-thread.html Simon

I have been using Futaba 3008SB and 7008SB which have the same voltage specs as the 3004SBB with 2S LIPOS for ages without any problems. This thread worried me so I contacted Futaba and they have just confirmed that the 7.4V limit is for the nominal voltage level and that a battery fully charged to 8.4V is fine. So it is OK to use these receivers with a 2S LIPO Simon

There definitely seems to be some sort of problem here. From the BMFA home page, if you click on the 'join us' button, you get a broken link. The same thing happens if you try the 'contact us' links. So any potential newcomer to the hobby may miss out and even give up. I suspect that this is just some minor temporary glitch but it does need to be sorted out asap. Simon

According to their website they are Taiwanese. I've not seen one myself but I have heard very good things about some of their other engines from people I trust. Seems like a low risk, if you are in the market for that type on engine. Simon

Hi E.D., I think you are right - this file shows all OS engines from 1936 to 2020. The 90FS from 1983 is very similar in layout to the 60FS and 75FS but does have rocker covers O.S.1936_2020.pdf Simon

In theory yes - although there is no battery hatch and so this needs to be thought about. As a coincidence, I have just started building a Tracer for electric as an experiment. I am changing the way the wing is mounted with two cap screws a couple of inches back from the LE and another two at the rear. This means that with suitable ply spars (a recommended mod anyway), I can remove a bit of the front of the wing, hopefully enough to get a battery through and then have the top fairing / canopy a removable hatch cover. At the moment, it is just a few thoughts and I don't know for certain if it will work, but I am fairly confident. I've got a lot of things on at the moment so not sure how long it will take me to get it done but it will probably not fly until next year now. If it works, then I'll put some pics and more details on the forum Simon

The Tracer is certainly a brilliant plane and is a cheap way to get your thrills. If you race them, then you have to use an APC 8x8 prop, but if you just want to fly them for fun, like myself, I would recommend using a 9x 6 prop which is nearly as quick in a straight line but makes hand launching much easier - I just get airborne with an underarm lob. I would highly recommend giving these planes a go

You can still get them today through Barry Lever at Pylon-line. Now they are powered by West 32's in the club 32 class. Absolutely brilliant fun to fly as an adrenaline rush, even if you don't want to race them.

Easy Composites and Buck Composites both do strip, rod, round tube and square tube and some angle but not channel or beam: https://www.easycomposites.co.uk/cured-composite-materials https://www.bucks-composites.com/categories/carbon-fibre They also do all the other things that you are likely to need Simon

The Peatol lathe is actually American made and called Taig in USA. Back in the 70's when it first came out my dad considered importing it commercially and we tried them out quite a lot. For what it is, it is OK but the some of the aluminium slides wear out quickly and the tailstock used to jam up. Fine for very small simple jobs but not as versatile as the others being considered here

All, I don't think that there is only one manufacturer and that all the lathes are basically the same. There are two well known and respected Chinese manufacturers of small machine tools - SIEG and WEISS, and there are probably many others. Axminster and Arceurotrade actually state that there machines are SIEG but other brands do not say who makes them. I am pretty sure that Warco use WEISS for their 'WM' range but I do no know who makes their 'mini lathe. I have a Warco Super Mini Lathe from about 6 years ago and it is similar to the SIEG products but definitely NOT a SIEG with some subtle but significant internal differences. I am also pretty sure that Warco's current supplier of the mini lathe is different again. Whatever brand you finally decide on, to a greater or lesser extent, they all benefit from a bit of work and a few modifications. I would say that 'as supplied' my lathe was very poor performance but after some simple adjustments to the gib strips etc, it got a lot better. Then I added extra adjustment screws to the gib strips, honed the slides and changed the main bearing to angular contact types. The transformation was dramatic and it is now very good. Siimon

Back in the '70s, I used to race electric cars with Futaba 27MHz am gear. The motors were brushed, often with worn out brushes casuing a lot of sparking and none of them had any suppression components fitted at all. The only time I ever got any interference was when someone else turned their transmitter on, on the same frequency. It should be fine! Simon

I have a T18SZ which is essentially the same and there are a number of ways to achieve what you want but probably the simplest is: 1. Setup your main motor in the usual way 2. Setup the secondary motor on another channel that you are not using and make sure that the control is set to the throttle stick (either J2 or J3 depending on which mode you fly) 3. Setup the throttle curve for the secondary motor to whatever works best, which is probably the same as the main motor. 4. Setup a dual rate function on the secondary motor channel to be operated by the switch that you want to turn the motor off 5. Flick the switch to the 'motor off position' and then use the AFR function to setup a throttle curve on the seocndary motor that is just a flat line at minimum setting (best to use the point or spline type curve). If you are used to using flight modes (conditions), then I would recommend doing the above except for setting up different flight modes and then setting up the throttle curves as per above. The advantge of using flight modes is that you can also change any other thing, like the rates, trims etc all at the same time. I hope thsi makes sense? As I said, this is a very versatile TX and there are many ways to achieve the same thing, what I am suggesting is only one way of getting there and there may be others that work better for you. Good luck Simon

I have been a subscriber for nearly twenty years. I cant remember using the digital archive back then, but certainly have had it for many years before Covid.

I was told that I might have access on August 4th. It still doesn't work, so I asked again for a definitive date and am now being told that I will have access on August 17th. I agree, it is not very good to have an unreliable promise to restore something that you always had, especially as it is costing me more and I have to pay in a less conveneient way! I might also consider not renewing next year. Simon