Robert Parker Posted February 17, 2019 Author Share Posted February 17, 2019 Hi All, It's been a while since I last worked on the Dornier having had a bit of a distraction and built myself a DB Bi Stormer. I have spent some time today looking at the Dornier and trying to catch up on my train of thoughts back in September and having wired and installed the motors back then and am now a bit puzzled. For some reason, which I cannot recall I have fitted 3530/14 motors with 30amp ESC's oops, these motors require a 50 Amp ESC. I think I must have ordered the wrong size or had a senior moment again. If I kept the motors and bought new ESC's they would be a tight fit in the outer nacelles and almost impossible in the centre one plus I am a little concerned about the heat / cooling Central nacelle, a bit crowded without the ESC and the incoming power cables Possibly a twin with freewheeling central prop? That's all for now Regards Robert Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 17, 2019 Share Posted February 17, 2019 I am a little confused Robert. If these are the motors you have, they are rated at 22A max so a 30A ESCs should be fine. If you are planning to use a 4S lipo (nominal voltage 14.8v) and prop them to their max 22A (not advised generally) you will have 325W per motor or in the region of 975W for a 9lb model. Should be OK for a model of this type, I would have thought? Perhaps I am missing something? Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted February 17, 2019 Share Posted February 17, 2019 Hi Robert, Apologies for not being able to give you any kind of advice here regarding your speed controllers, but at least I feel that you might have your mojo back for your Dornier. Not that sure when following Piers's link that that particular J3 really needs an ESC... Never thought one would start a 3530 with an IC 'stick'... Well at least learning a bit every day, ain't it? Cheers Chris Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 17, 2019 Share Posted February 17, 2019 Ops, should have been this motor! Now everyone is confused! Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted February 17, 2019 Author Share Posted February 17, 2019 Hi Both, As I said I'm trying to get back into this model and why I had got 30Amp ESC's, however, now this is possibly where I have confused myself, looking at the motor data sheet which is the same as Piers 2nd link and click on upload files then click on motor instructions it states 50Amp. Though I must agree with a 30 Amp ESC should be OK with a max current draw of 22amp just puzzled why instructions call for a 50Amp. Regards Robert Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 18, 2019 Share Posted February 18, 2019 I think it is because you are dealing with Hobbyking instructions and something was 'lost in translation' on this occasion. Robert, could you confirm that you are planning to use a 4s LiPo, as you are not going to get enough power on a 3s with this setup, I would have thought? Also, how did decide on the propellers you have fitted? The spec sheet for this motor suggests an 8 x 4in on 4s but that is for a two blade prop, so presumably you are using something like an 7 x 4in, three blade prop. ? Hopefully you have tested your setup with a watt meter in any event. A great project Robert, thanks for sharing. Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted February 18, 2019 Author Share Posted February 18, 2019 Hi Piers, I was hoping to use a 3s set up but I do have a 4s which I would need to make some slight adjustments to the battery box. As for prop sizes, I assumed i would be using a 3s setup and from the instructions prop size for 2s = 12 x 6 and 4s being 8 x 4, therefore, 3s would be 10 x 5 for a two blade and using a rule of thumb to down the diameter an inch for three blade, but a 9" prop would fowl the fuselage so by physical restraints I went for 8 x 4 x3. Now that I have aired my thoughts I hopefully do some testing this week with different prop sizes. Will keep all informed of the results. Regards Robert Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 18, 2019 Share Posted February 18, 2019 3s LiPo (nominally) 11.1v x 22A (max) = 244.2W per motor, x 3 = 732.6W total input. I thought that it could be a little marginal with a 9lb model but then again it has a good sized, highish aspect-ratio wing, so it could be fine. Might struggle a bit off water if that is your plan? With any luck the testing with different props will prove me wrong. Good luck. Be interesting to hear what others think. Edited By Piers Bowlan on 18/02/2019 06:47:20 Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted February 18, 2019 Author Share Posted February 18, 2019 Hi All, I have just carried out some prop tests this evening. Here are the results, Firstly, I just connected up a single motor. Not wanting a repeat of Saturday's disaster where after connecting a 4s battery to my TN Lancaster following some repairs and wanting to check out why she behaved so different from the previous flight to which I managed to burn out all 4 ESC's in a matter of seconds even though they were marked 2 - 4s, a smoking model in doors is not a good sight thank goodness the wife was out and the smell had gone by the time she returned. So new ESC's ordered along with new motors just in case. So back to the Dornier, the props and batteries were what I had to available, the order of the test was 3 blades first as they were already fitted then the 7 x 5 and then the 8 x 5 props. The batteries were all freshly charged at the start of the testing period with each motor run lasting a few seconds. single motor fitted with 8 x 4 x 3 blade Battery 3s 4000 167Watts 3s 6000 172 Watts 13Amps 4s 5000 402 Watts 3 Motors running 7 x 5 2 blade APC props Battery 3s 4000 333 Watts 29Amps 3s 6000 365 Watts 30Amps 4s 5000 723 Watts 46Amps 3 motors running 8 x 5 2 blade APC props Battery 3s 4000 433 Watts 38Amps 3s 6000 472 Watts 40Amps 4s 5000 935 Watts 60Amps 3 Motors running 8 x 4 3 blade GWS props these do seem a little flimsy and may flex I think Battery 3s 4000 434 Watts 38Amps 3s 6000 470 Watts 40Amps 4s 5000 950 Watts 62Amps So it looks like I have to modify the fuselage to take the 4s, it is only just a bit too big to fit. I have no intention flying off water with the exception when our field becomes water logged. Any thoughts Piers or others on the above Regards Robert Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 19, 2019 Share Posted February 19, 2019 Well, as no one else has put their head above the parapet (!), I would be inclined to fit the 8x5 two blade prop and run it on the 4s LiPo. After all 935W is near enough 100W per lb as a ballpark figure and 60A is 20A per motor, so within the 22A max. Also a 7x5 three blade prop might be enough on 4s too, if you want scale fidelity. On your earlier photo, showing just 8mm clearance between the prop tip and the Fuselage, presumably that was with the 8x4in three blade prop fitted? I just wondered, as if you want to stick with a 3s LiPo could you try a bigger prop (9x6) but if no room, the other options are a higher kv moto r- or bigger motor. Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted February 19, 2019 Author Share Posted February 19, 2019 Thank you Piers, The 8mm gap is with the 8 x 4 props, the 8 x 5 is a contender but I might try some others later on. I do think the 4s is the battery so I'll have to alter the battery compartment but not until I have done a trial balance as I was way off on my FW 200 Condor and had to move the battery back 8", though that is part of the fun of own designs. Regards Robert Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted March 2, 2019 Author Share Posted March 2, 2019 Hi All, A bit more done today including re-calculating the CoG position as this has been on my mind since my terrible maiden attempt of my FW 200 Condor which had a major CoG error, the new position is 12mm forward of my original position possibly due to the weight gain. Her she is just a few seconds after opening the throttles, yes that's right just a few seconds it all happened so quick I did not have time to react. This remarkable Image taken by a fellow club mate, just before impact and the resulting damage helped put me off working on the Dornier and a lot of self doubt set in. All of the damage has been repaired and she is waiting to have another go, CoG moved a lot further forward after re-checking and confirmed by a fellow modeller. So, back to the Dornier, I have modified the battery box to allow a 4s lipo to fit and drilled for the wing retaining bolts. Following that although there is still a lot to do I balanced the model and at least the battery box is in the right place and in it's present state the battery is at the rear end of it, so hopefully after finishing and painting I'll still have some room to play with for the battery position The battery can move right up into the nose if needs be. That's all for now Regards Robert Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted March 10, 2019 Author Share Posted March 10, 2019 Hi All, Made a little progress, the biggest being what to covering type to use. I had thought about using tissue and Poly C which is what I used on the Condor. After some thought and knowing that she will be belly landing on grass, I wanted something hard and durable and I was going to glass the bottom of the hull anyway, so I thought why stop at the hull. I know the shape of the fuselage will be challenging but I will do the same as when i built it and that is one side at a time, hopefully not ending up with a banana. Never, glassed before so this will be the first for me, always willing to learn. So I have now got all of the materials I need and made a start by giving the entire model a coat of sanding sealer. That's all for now Regards Robert Quote Link to comment Share on other sites More sharing options...
Bucksboy Posted March 10, 2019 Share Posted March 10, 2019 Have a look at the Bucks Composites site, he gives advice on glassing using foam rollers. I’ve glassed four planes and it gives great results and very easy to do. Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted March 16, 2019 Author Share Posted March 16, 2019 Hi All, I have made a start on the glassing on the wings, put it off for a bit, a process I've not done before, well not for around 30 years anyway and the products I used then were from Halfords and it was only a cowl, got good results though. Back to the present day, well I must say the task i had been putting off was a real pleasure to do and as I was using Poly C I could use it in the kitchen with no hassle from anyone else in the household. Underside done, now on the topside, this is even better than using tissue no bubbles no tears and so easy to work with........ I even covered the nacelles with the same piece as the wing just a single relief cut at the back of each nacelle and it was done, why have I not used this stuff before. I used Poly C and tissue on my FW 200 Condor. On with the second coat to start filling the weave, by the time I was ordered out both sides of the wind and ailerons plus flap all had two coats not bad in three hours plus Wales won - perfect. Next more coats to the wings to continue filling in the weave plus sanding sealer to the fuselage and continue making a new wing for my TN Lancaster just to keep me busy. That's all for now Regards Robert Edited By Robert Parker on 16/03/2019 19:27:41 Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted March 17, 2019 Author Share Posted March 17, 2019 Hi All, More applications of Poly C to the wings today as well as experimenting with the receivers. I intend using two receivers on this model to make life a little easier at the patch, 1 located in the fuselage operating the rudders and elevators and the other in the wing for everything else. My radio equipment is a Spektrum DX9 using a 4 channel receiver in the fuselage and a 6 channel receiver in the wing. I bought a new AR620 as it has no antenna and a AR400. I have never done this before even, so all set up TX on and in bind mode and both receivers in bind mode and both bound successfully however, on switching off both TX and RX's remove the bind plug and switched on Tx then RX's the 620 worked but the servos connected to the 400 barely moved, both RX's had separate power packs. Tried them both individually and they both worked fine. So attempt 2. as above but changing the AR620 for a AR610 and re-bound both RX's bound and worked perfectly. I now have my receivers sorted. 3rd, 4th and 5th coats being applied so far. In the background my new wing for my TN Lancaster is coming along well as the old one was beyond repair following a hard landing, new wing has liteply ribs and nacelle formers instead of balsa hopefully not added too much weight but gain strength.. Well back to give another coat of Poly C. That's all for now Regards Robert Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted April 25, 2019 Author Share Posted April 25, 2019 Hi All, Due to work commitments I have not done a great deal to the Dornier over the past few weeks. I was a little disappointed with the Poly C as in a few areas the sheet covering warped / wrinkled in a few places but with a shape knife and some cyano most of them went back OK except for an area over the flap where the grain runs diagonally and I have a nice rippled effect which I have sanded and filled to be acceptable. I have this week made the outer wing struts and changed the method of fixing to the sponsons as I was not happy with just using a wood screw so I opened up the underside of the sponsons and epoxied blind nuts on the hardwood I had previously fitted, much happier now. Well mostly anyway, when I fitted the rear wing struts they did not align with the front ones as I had hoped. Still not the end of the world just looks a little odd from the front. The wing is now very solid and in parallel with the tail, now to patch up those holes and figure out how to make the diagonal brace between the front and rear cabane struts. Next I need to get the fuselage upto the dame level as the wing so more Poly C and cloth and decide how I'm going to get power from the battery in the fuselage to the wing, two ideas in my head at present. That's all fro now Regards Robert Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted April 25, 2019 Share Posted April 25, 2019 Those struts are aluminium? I would simply use them! Positive for the middle pair, return down the longer outer four. . Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted April 25, 2019 Share Posted April 25, 2019 Hi Robert, Nice you're back to the Dornier. Regarding the 'swollen' sheet, I don't know if you did it, but best is to cover the balsa with a thin layer of sanding sealer before applying the glass coat & Poly-C. It avoids the wood to absorb too much water during the process. Keep it up, young man. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted April 25, 2019 Author Share Posted April 25, 2019 Simon, I wish I had thought of that earlier in the build, but there may be a way, just need to think a little on it. Chris, I did coat the whole model in sand n seal, which is water based and no problems arose when I applied it it was only after I started applying the Poly C, at first they went back but just stayed there. I try to avoid using traditional sanding sealer / dope as my workshop was a spare bedroom before building the benches. Wanting to prevent my wife from complaining any more than she needs to I do try to avoid strong odours of paint, dope etc which I do outside and leave the model in the sun house overnight to dry if I can get away with it. Regards Robert Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted April 28, 2019 Author Share Posted April 28, 2019 Hi All, Well having given Simon's suggestion some thought I went ahead with electrifying the struts, although front positive and rear negative These self tapping screws to be locked in place with cyano. Before fixing in place the connections were given a good pull to check the crimping was nice and tight. These two connections will be bolted on when the wing is attached using spring washers. Probably not the neatest solution. I have carried out a voltage check, 12.35v at battery and 12.35v at the struts. Now I have sorted this out I can resume finish off sheeting the hull. That's all for now Regards Robert Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted August 1, 2019 Author Share Posted August 1, 2019 Hi All, It has been a while since I have done anything to the Dornier. Having intended spending some time carrying out house renovations this turned out a to be a bigger and more expensive project that expected, still I have built up a fair decent amount of brownie points from the wife who is VERY happy with the end result. so much so that I think I have started her thinking of what's next.........uuummmmmmmmm, time to disappear back into the workshop for a while. Anyway back to the Dornier, this week I have glassed the fuselage along with many many coats of Poly C and am now looking forward to spending my time with the wet "n" dry, at the moment there is nothing to really show as the poly C dries clear and it all looks like balsa. I have also been fighting the urge to start another model as I'm missing the building part. That's all for now Regards Robert Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted August 2, 2019 Share Posted August 2, 2019 Hello again, Robert; Great to have you back in the shed.... and with a load of 'brownie points'. If I'm allowed a suggestion, instead of 'overloading' your FG with coats of Poly C, why don't you try out the Freddie B formula? It's lighter, a lot easier to sand and gives a perfect finish even used on blue foam or Depron. You can find it in my 'old' Ballerina build blog. Please have a look at page # 43 & scroll down a bit... really worth trying. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted August 3, 2019 Author Share Posted August 3, 2019 Hi Chris, Thank's for that, I having read your Ballerina post, I recalled reading it at the time and over time it faded away in the old grey matter. Now printed off and filed for use. Regards Robert Quote Link to comment Share on other sites More sharing options...
Robert Parker Posted August 11, 2019 Author Share Posted August 11, 2019 Chris, all I can say is wow "Freddie's formula", is great and as you say easy to sand though must add that a FFP3 or above dust mask is a MUST Fuselage now ready for painting perhaps might get a coat on this evening if it stops raining long enough. I'll try the wings next, which to be honest have not worked out as good as I had hoped for. That's all for now, hopefully some photos next post. Regards Robert Quote Link to comment Share on other sites More sharing options...
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