Greybeard

Posted by Mike Hardy on 21/10/2013 14:29:45: Hi, My 63" arrived today, Next - to generate a wood list. I notice there are shapes to be cut from adhesive backed paper then stuck down. I take it you remove the paper once the shape has been cut from the balsa? Mike You do remove the paper after shaping the parts although sometimes it is reluctant to come off. Before you start cutting I advise that you check the dimensions against the plan where possible as on my 88" there were a lot of discrepancies that needed correction.

Posted by Martin Harris on 20/10/2013 18:37:56: I consider that a club rule to protect others is a good thing, hence we don't allow "live" models of any kind behind a certain point. What a club could and should do is to encourage its members to be aware of any risks and adopt practices to minimise any personal risks. For example, I won't allow a student to reach over a spinning prop to remove their glow connection, or carry a model with the propeller pointing in someone's direction - including electric models, which hopefully ingrains these behaviours into them when they are operating without supervision. Thinking about when to arm an electric model and how to restrain/handle it is something to be done from the start and I find the least receptive to be older experienced pilots who were brought up in the predominantly IC days when electric power was a bit of a contradiction in terms! Thank you Martin, that is what we are working towards but have to establish "best practice" first; hence this thread.

Posted by john melia 1 on 20/10/2013 10:18:21: i take it you meant "cannot face" nylon and dope ? i dont mind having to sand a lot , i've never used nylon and dope , any tips ? Sticky keyboard, at least that's my excuse. Tips for nylon and dope! Don't do it in doors would be the best advice I can give.

In my experience the six or so hand injuries I have witnessed from i.c. engine operation have come from two causes, one is reaching through the propeller arc from the front to adjust the needle valve, and the other is grabbing at an unrestrained model that has started to move and catching the propeller. The point has been made that electric motors react to obstacles in a different way to i.c. engines insomuch that they increase power when meeting an obstruction, so carry on chopping for longer than an i.c. engine that tends to stall on overload. Electric power should be safer to operate than i.c. we simply want to make sure that it is.

Profilm is much better and tougher than Solaspan so that would be my recommendation; that's if you canno tace nylon and dope.

My unease with the proposals in my O.P. stem partly from my distrust of electronic switches and the likelihood of them failing to the live state. No one seems able to give me a guarantee that this cannot happen therefore I must assume that it can and at some point will. I use the same philosophy when buying lotto tickets. Secondly the use of an inhibiting switch invites both confusion and complacency so I have little confidence in that method either. Turning the transmitter off and relying on the live receiver’s failsafe on 2.4 systems may be the best way forward but I am suspicious that interference or a receiver fault could still activate the system. The more I think about the problem the more convinced I am that a mechanical isolation device in the battery circuit is the only safe way to proceed.

Posted by Max50 on 20/10/2013 08:19:12: If you arm the model at the flight line; how do you restrain the model, while holding the transmitter and plugging in a safety connector. I wouldn't like to put my tranny down on wet grass while restraining the tailplane and plugging in a connector. If you had a restraint at the flight line then that would take one action away, but i would think a condition hold on your transmitter in the pits would be better, and be part of your SMART checks. As an i/c flyer i was wondering what steps you electric guys take in arming, as an electric motor wants to still keep turning whatever is in the way. What do the competition F3A people do with their mainly electric planes? Quite interested to know?. Also if you're taking your 'A' or 'B' test with an electric; what is the examiner looking at with this action of arming, and where the arming should be done? We have a model restraint stand near the flight line which has a transmitter stand incorporated.

Ben, most commercial kits and plans are over designed from the structural point of view, they have to be because it's not known how they will be used or abused. It follows, in my opinion, that most designs can be lightened considerably if you are a confident flyer and have a sense for structural engineering as your background suggests that you have; however I'm not sure that steel shares the same grain structure as steel.

Posted by Martian on 19/10/2013 19:15:30: Hi Greybeard my lipos are 3s 2200 mah I feel like a proper modeler now I have 4 planes on the go and non of them kits Edited By Martian on 19/10/2013 19:16:37 Four active models, I'm impressed. I guess a 3s 2200 mAh lipo should power a 1.5Kg model of the Barnstormer type, so I would go with Phil's suggestion above and go with the 52" size.

I’m not afraid of electric flight, neither is anyone else that I know of, but the medium has an inherently higher risk over i.c. engine insomuch that an apparently benign motor can become active unexpectedly by for example catching a throttle stick with a lose neck strap or simply because the operator forgot that the model was armed. I for one have seen enough of other people’s body parts together with associated blood and flesh flying around a pit area not to want to see a repeat performance. The point of my question was not to find out who suffers from an electric flight phobia but rather to glean sensible ideas or experience of the points I raised in the opening post. I would like to know, for example, if it is possible for a powered but shut down ESC to fail to an active state such that the motor will run. In other words could the motor start with the receiver in failsafe mode?

Posted by Martian on 19/10/2013 17:52:56: Still undecided as to which Barnstormer pref it will be one the will fly on 3s batts cos thats what i have Two in series make a 6 cell pack which is what I plan do, the more important number is probably the mAh rating.

Posted by ken anderson. on 19/10/2013 16:34:28: ok GB....I would have thought a half way box would be the way to go.....keep the models and pilots away from the runways when they are connecting/ disconnecting the batts.....as there is nothing worse than someone on or near the strip messing around with a model when other flyers are attempting to land / takeoff..... ken Anderson.....ne...1 .......proposal dept.. I agree but that does involve carrying a live model which is something we wish to avoid. Your input is appreciated.

We want to adopt the best safe practice so are investigating all proposals hence my request for input from those here.

Your heading suggests that you started this thread as a place for the general discussion of Barnstormer issues hence my chiming in; am I wrong?

We had a discussion at my club on ways to improve the safety of electric flight systems in the pits and transit to and from the flight line, in particular methods to prevent inadvertent starting of the motor. We already follow the requirement that the models failsafe should be set to stop the motor on loss of a proper signal. One idea is simply to delay the connection of the battery until the model is on the edge of the landing strip and to disconnect it there immediately on landing. This is fine if the connection plug and socket is readily accessible or if a suitable arming plug is fitted as has been discussed in other threads. As an alternative we have a proposal to rely on a spare transmitter switch mixed through a spare channel so that it inhibits the throttle channel thereby preventing operation of the throttle. The idea is that the throttle can then only be brought into use by moving this switch to the “on” position so that the throttle channel becomes operative. This, it is felt, will allow the batter pack to be connected in the pits and the model to be safely carried to the flight line without any possibility of the motor starting even though the motor and ESC is live. Yet another proposal suggests turning the transmitter off prior to delivering or collecting ones model from the strip so that its receiver goes into failsafe and thereby ensuring that the motor cannot start. I will welcome others thoughts on these proposals in order to help me clarify my thought as at the moment I have some unease with the latter two ideas.

Depends what you are building, I've removed 5 grams from a rudder this morning by inserting holes and I consider the effort worthwhile; others may not. Forstner bits are very good for drilling blind hols in softwood but nowhere near as good as the grit cutters mentioned above for cutting holes through balsa. I have both types by-the-way.

Posted by Toni Reynaud on 18/10/2013 18:42:27: Another thought on the Arming situation is to put the Arming connection (such as those described above) into one of the three leads to the motor. This will allow the motor to act as loudspeaker during initial switch-on and battery checking, but with one phase effectively removed from the motor input, the motor can't turn. End result is a system which allows checking of the radio system without the possibility of the motor running. I'm not completely sure of the electronic theory at work but if you did this to a mains three phase motor you would risk burning out the motor.

I disagree with Danny and Peter, every gram saved is a worthwhile saving and will result in improved performance. One gram off the average tailplane for example will result in 5 grams less nose weight being required. Lighter models have a wider speed range and can land more slowly than a heavier ones.

The instructions for the 88" contains an unquantified wood list which is not very helpful, I just ordered sheets of the appropriate thickness and appropriate grade and strip off the parts required.

For small clean holes up to about 10mm in balsa I use sharpened bass tube, over that size I use the cheap diamond grit tile cutters mentioned above. All are used in a pillar drill. For plywood I use standard wood bits.

Posted by IanR on 17/10/2013 22:53:14: Erfolg, is this the kind of thing you're looking for? **LINK** Ian I'm supprised that no one markets these in the UK, I imagine that they would sell well.

I have some 6mm plugs on order so that I can make up a plug such as Chris illustrates, in my case it will be housed under a flip-up hatch cover.

Posted by BayNavigator on 17/10/2013 18:51:26: How about the biplane versions, the 58" & 72" Bi-stormers? I have an unstarted 58" version. I might just make it my next build. You could leave the lower wing until later.

Thinking on this subject further it is probably better to use a different style of connector for the plug to those used on the rest of the system to make it harder to connect the shorting plug directly across a battery. My club has a simple rule regarding electric models and it is that batteries are only connected on the strip immediately before takeoff and disconnected immediately on landing. Further advice on the use and fitting of battery isolation switches can be found on page 27 of the BMFA manual.

It's worth doing a search as this subject has, I think, been discussed here many times. Purple Power list them as Battery Plugs others call them Arming Plugs. Since the plug carries the motor current it should be made from the same connectors that you are using for the rest of the system. .