Robert Edney Posted February 23, 2018 Share Posted February 23, 2018 Hi chaps, the last time I started a new thread while still on the same build I got a bit of a telling off, I did post this question on the other thread but got no response so at risk of offending anyone here goes, I have taken the term taking my time to another level but I am finishing the covering which is not as easy as it looks on you tube but I'm getting there, I have got the servo,s , radio and ordered a brushless motor kit with ESC and prop. Finally the question, it says to use a 3s battery but I'm confused with what one 1500 my etc there seems to be so many, I am quite pleased with my build so far and can't waste money on something that's not right, any help would be great. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted February 23, 2018 Share Posted February 23, 2018 There are many factors that affect "which battery" There is the question of size and weight - the bigger the battery the bigger and heavier it gets - obviously in any model there is a physical limit to the dimensions of the battery, there is also the question of weight - the Lipo is one of the heaviest things in the model so it will have a dramatic effect on balance - in most models the battery needs to go as far in front of the desired CoG as possible to avoid having to add (dead) weight to balance it - most people if they need more weight up front use a bigger capacity battery rather than lead Secondly there are the electrical questions? Duration of your flight and the ability of the battery to supply the current demanded by the motor/prop combo To estimate duration we need to know the current drain - that can be established roughly by taking a reading of the amperage at half throttle - divide the battery capacity by the current drain and yo have a rough estimate of duration of flight - the bigger the capacity the long the flight The current draw by the motor will vary with the prop you fit, a small one will use less current but provide less thrust, a larger one will give more thrust but use more current So where do you start???? We have a 3S 1500 Battery - you have ordered the motor, esc and prop - so when those arrive the best thing is to set up a test bed - fix the motor to a lump of wood (not balsa) and shove it in a vice- connect up the radio and bing in the ESC and test the motor WITHOUT the prop, you will need a WATT METER to check the current draw is below the ESC Rating with the motor running- now fix the prop and again read the current - it will have jumped up a LOT.... make sure that at full throttle there is still at least 15% headroom between max current drawn by the motor and the ESC rating As a rough (very) guide to power you will need (ish) at least 100 Watts per Lb of model for a typical training/sports model If you motor/prop/battery combo gives at least that - then great, if not one of them has to be changed Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted February 23, 2018 Author Share Posted February 23, 2018 All I wanted was to build a little plane and see it fly not send men to the moon, now this is starting to get silly, I'm certainly not going to start buying watt meters etc, surely there must be some sort of scale like for an 800g plane a 3 s 1000 mh lipo but you're starting to scare me with all the scientific stuff Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted February 23, 2018 Share Posted February 23, 2018 The intention was not to scare you, but without details of the plane its an impossible question to answer and rather than just ignore you I was trying to illustrate the variables if the plane is 800g then you will be looking for around 150Watts To get 150 Watts from a 3S lipo then you will be pulling around 12 Amps max - so say 6 Amps average So your 1000Mah lipo will give you around 5 minutes flying time - give or take So its a reasonable set up so far What motor and prop have you ordered? Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted February 23, 2018 Author Share Posted February 23, 2018 I bought it from Amazon as a kit it says it is for models in the 700-1200g range, 800 being optimum, I don't know how to post links but the reviews all seemed positive so I bought it, if I had known I would have waited but I thought seeing as my plane is in it's optimum range it would be OK and then I only needed a battery, never mind Quote Link to comment Share on other sites More sharing options...
Pete B Posted February 23, 2018 Share Posted February 23, 2018 All of Dave's advice above is sound, Robert, as the reality is that mismatching components such as motor, ESC and prop can easily result in having a model that has too little or too much power, or even prompt an unwanted electrical firework display! In your model's case, however, it's a simple motorised glider, so the size of the battery will dictate the duration of the power run, as you'll find you'll just use the motor to climb to height then glide, repeating until you've used the available battery power. With any glider, it's important to not add unnecessary weight which will degrade the gliding performance, so I'd go for a battery that is sized to a) fit the available space and b) provide sufficient weight at the nose to balance the glider at it's correct centre of gravity without needing extra weight, if possible. If your model is flight-ready, apart from the battery, then balance the wings on the C of G indicated on the plan and see how much weight is required to achieve the balance point. Then choose a battery of about that weight, provided it will fit in the model. For example, a 3S 1300mAh pack weighs about 100g, a 1600 mAh about 140g.Either of these should give you several climbs of a couple of minutes, sufficient to gain height. Once you've established how much weight is needed, then research the available battery packs at your LMS or one of the online retailers and buy accordingly. The fact is, it's not a 'one size fits all' hobby - you have to do your research to get the best possible result - and that's what makes it such an absorbing hobby! Pete ps - to post a link, just copy the address of the page, click on the link symbol 5th from right on the bottom row of the reply box and paste the address where indicated and click 'OK'. That's it! Edited By Pete B - Moderator on 23/02/2018 18:28:53 Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted February 23, 2018 Author Share Posted February 23, 2018 Thanks Pete now that makes good sense to me and obviously I hadn't thought about it like that but that Doe's sound like a good idea, killing two Birds with one stone Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted February 23, 2018 Author Share Posted February 23, 2018 **LINK** Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted February 23, 2018 Author Share Posted February 23, 2018 I think I did it if I did that's what I bought Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted February 23, 2018 Author Share Posted February 23, 2018 Finally posted a link to what I bought and everyone went out, LOL Quote Link to comment Share on other sites More sharing options...
kc Posted February 23, 2018 Share Posted February 23, 2018 Well they probably didn't reply because there is not enough info on that motor to give any opinion! When you get the motor tell us the motor numbers and details of the ESC. Then people can offer more advice. Quote Link to comment Share on other sites More sharing options...
Dickw Posted February 23, 2018 Share Posted February 23, 2018 Scroll down a bit on that link to see motor details as follows:- Motor Weight(including connectors): 70g Size: 27.5x30x30mm RPM/V: 1500KV ESC Constant current: 40A Weight:39g Size: 45x24x9mm Prop 7'x5' As said before, pick a battery sized to fit the space and with a weight to get the CG right, but something around the 1200mAh mark should be a good starting point. Dick Edited By Dickw on 23/02/2018 20:37:32 Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 4, 2018 Author Share Posted March 4, 2018 I was doing the covering with the iron from the kitchen and melted it once or twice so I have ordered one from hobby king but I've got to say for my first attempt I am quite pleased, I've put some photographs in my album, what do you think, I hope it fly's Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted March 4, 2018 Share Posted March 4, 2018 Judging from the size of the table Robert, then you have built a nice looking small glider. I have such a model using 2s and 3s small lipos about 1000mah, and using a 20A ESC As the model is just power assisted for gaining height, then essentially a glider. Was a power assisted glider your intention? As no undercarriage is in the view Or a fully rise off ground aeroplane, where power is used throughout the flight? Edited By Denis Watkins on 04/03/2018 21:31:50 Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 4, 2018 Author Share Posted March 4, 2018 There was no undercarriage on the plans which worry's me a little bit as I think the tail might get damaged on landing, but it was always going to be a power assisted glider, may be when I trust my gluing ability I might try to build a bungee launched plane but I have visions of it breaking up on launch, but I must admit that I think I got the bug and am deciding what one next and this one hasn't been out the house yet Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted March 4, 2018 Share Posted March 4, 2018 OK Robert, hang fire buying anything else. Am guessing 40A is over the top And doubt the airframe will carry a 1500mah pack Could you type out the wingspan of the glider, and flying weight from the plan if it is there Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 5, 2018 Author Share Posted March 5, 2018 The glider is 1500mm and about 800 g but I don't know if that is with all the motor kit and stuff or just the plane Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted March 5, 2018 Share Posted March 5, 2018 Apologies Robert, I just read through, and you have good advice and predictions on the 40A set up you bought. My concern is the model in the picture does not look to be 28oz/ 800grms And as a powered glider, it does not need motor thrust all of the time. Apologies Robert, but now weigh the build on that table, and come back with the result Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 5, 2018 Author Share Posted March 5, 2018 I just double checked the measurement and it should fit snugly with a little sponge around to stop it flopping around Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 5, 2018 Author Share Posted March 5, 2018 Unfortunately I have no scales but just looked at an e-mail from the supplier and he said the one he built was in the 750 760 range and said mine would be about that depending what wood and covering I use Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 5, 2018 Author Share Posted March 5, 2018 Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 5, 2018 Author Share Posted March 5, 2018 Battery arrived, fits OK, just waiting for the motor and the iron to finish the covering and then we will know, Doe's it f!y??? I really hope so after all this! Quote Link to comment Share on other sites More sharing options...
kc Posted March 5, 2018 Share Posted March 5, 2018 Robert, Two things came to mind when I saw the fuselage photo 1. Lipos have to be secured -usually by a Velcro strap and a Velcro patch on the Lipo to stop them sliding back and altering Centre of Gravity. 2. 'Snake' outers need to be firmly supported near servo and near elevator All that sort of thing would be checked by a competant instructor before test flight, so it's best to sort this out at home first. It's free at almost all clubs so get an instructor at first rather than wrecking it on the first flight yourself Quote Link to comment Share on other sites More sharing options...
Robert Edney Posted March 5, 2018 Author Share Posted March 5, 2018 I will without doubt get it checked out at my local club and I still have to cover the rear wing, elevator and rudder and put on the control horns I only put the snakes in to find the right length and I will take them out before covering the fuselage and will put in a piece to support the outer part of the snakes, and will be making sure every thing fits snugly and is secure at the front. At the rate I'm going it will probably still be a couple of weeks till I'm done and will post some photographs when I think I am done Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted March 5, 2018 Share Posted March 5, 2018 Read kc again Robert, very sound vital advice. Those servos are set correctly at right angles When you connect the receiver, they more than likely go to neutral out of line Carefully remove the servo screw, lift off the arm and replace the arm as near to a right angle s it will go Then retighten the screw Neutral surfaces can then be set by adjusting the push rod lengths and using the transmitter. Get an approximate balance with fingers under the main wing spar and move the battery too and fro to balance. Do all the surface movement tests with NO PROP ON. With the PROP OFF Invariably there is power to the motor at set up time, so no prop on Ascertain the motor is off with the stick down If it is not, then reverse the stick with the transmitter. Google RC plane failsafe Also correct prop direction Also motor kill switch and electric motor Arm Plug, bought or made There is more to come Quote Link to comment Share on other sites More sharing options...
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