Lucas Hofman Posted March 23, 2017 Share Posted March 23, 2017 I will give it a try and leave it to you guys to judge if it is an improvement. Bit of a folly, since the inner struts will have a AL to AL joint. Maybe not if I can make the lugs from 1 mm brass bent in a fork shape. Still far away. Lucas Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 23, 2017 Author Share Posted March 23, 2017 Wings pretty much finished so as an excuse for more bench flying I thought I would have a weigh in and cg check.Currently 1.85 kg (4lb 2 oz) and 30 % chord . The battery can still move forward if needs must so with only the radio/servos and covering missing i am hopeful of managing without ballast. Tim Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 23, 2017 Author Share Posted March 23, 2017 Oh and the photo of where I am at... Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted March 23, 2017 Share Posted March 23, 2017 Very tidy Tim, Looking forward to seeing it covered...One of my most favorite parts of a build. D.D. Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 24, 2017 Share Posted March 24, 2017 Posted by Tim Ballinger on 23/03/2017 19:09:37: Wings pretty much finished so as an excuse for more bench flying I thought I would have a weigh in and cg check.Currently 1.85 kg (4lb 2 oz) and 30 % chord . The battery can still move forward if needs must so with only the radio/servos and covering missing i am hopeful of managing without ballast. Tim 30% chord on which wing Tim? If is is the upper you are good. Covering is quite heave (I guess 200-300 gram added) and most of it is behind the CG.This probably means rudder and elevator servo's should go as far forward as they can go. Lucas Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 24, 2017 Author Share Posted March 24, 2017 Top wing Lucas. Yes plan is for rudder/elevator servos right up front. I left the snakes as long as I could and will trim accordingly. Tim Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 26, 2017 Author Share Posted March 26, 2017 Since I was installing servos I also commissioned the esc (60A). Hence I could not resist checking the power output. So the 3548/05 consumed 47A and produced 700W on an 11x8 using a 4S. Pretty much the manufacturer spec. Might not be spending too much time on full throttle ! Tim Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 27, 2017 Share Posted March 27, 2017 What is the kv on that motor Tim? 700W sound a lot to me for a 2kg plane. But you can always set the endpoint of the throttle to 80 or 90% to tame it a little. Lucas Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 27, 2017 Author Share Posted March 27, 2017 Lucas, it's a 900KV . Tim Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 30, 2017 Share Posted March 30, 2017 A quick run of motocalc suggest you will nearly be able to do vertical ascents! Lucas Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 30, 2017 Author Share Posted March 30, 2017 Do you think I'll need to cover it first ? Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 31, 2017 Share Posted March 31, 2017 Not for the verticals. But you landings will be easier with covering on the wings too . Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 31, 2017 Author Share Posted March 31, 2017 Completed the radio installation, connected the top and bottom ailerons and everything appears to move ok so that's it for a few weeks while I am away. Then its final sanding , covering and a bit of cockpit detailing at the end of April beginning of May. Tim Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 31, 2017 Share Posted March 31, 2017 Nearly a pity to cover it Tim. What is the black stuff on the cockpit coaming? And what weight are you on now? Lucas Quote Link to comment Share on other sites More sharing options...
Martin Dance 1 Posted March 31, 2017 Share Posted March 31, 2017 Very nice build Tim, as Lucas says what weight have you reached now? I'm glad you're away gives me a chance to catch up between sessions on the allotment. So when you get back I should have a finished Skywriter and the start of the annual glut of courgettes! Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 31, 2017 Author Share Posted March 31, 2017 Lucas, She's 2.16kg . That's with all radio/servos/battery & esc. CG is at 35 % or 30% if I move the battery under the motor a bit more. See what the covering does but may struggle a bit without some ballast. The black stuff is soft automotive fuel tube slit down its length. Tim Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 31, 2017 Share Posted March 31, 2017 I hope to come this far before breaking for the summer, then she can hang from the ceiling uncovered until autumn comes. The fueltube looks very good, I will get some for the coaming. Your weight is inline with Lindsay's. He needed some ballast, but then he used heavy covering. You can still make lightening holes in the elevators and rudders if you want. It saved (on mine) 12 grams, which corresponds with 40 grams lead up front. But then, is 30-35% too far forward? The whole lower wing is further back. 35% sounds about right to me to get the average on 25%. Lucas Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 31, 2017 Author Share Posted March 31, 2017 Funnily enough I was just contemplating if putting holes in the elevators rudders would be a hedge against ballast. As far as cg position goes I was only going on Lindsay's write up which aimed at 70mm or 30 % of top wing. I did not read of him needing to change that so probably only flying will tell us more. Tim Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 31, 2017 Author Share Posted March 31, 2017 Guys , Found this on cg for stagger wings.... https://www.rcgroups.com/forums/showthread.php?519833-CG-on-biplanes-with-forward-top-wing Tim Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 31, 2017 Author Share Posted March 31, 2017 So if my sums are correct and assuming a 10% larger area for the upper wing (and hence a cg that is 0.45 of the distance between the 30% MAC point top and bottom wings) then the required cg is 93mm from the le of the top wing or 40%of the top wing MAC. Anyone care to check that ? Tim Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 31, 2017 Share Posted March 31, 2017 The CG on the plan is for sure a safe starting point. I would not be surprised if you end up with 5% further back after flying a while. But this is very dependent on how "neutral" you prefer planes to be - that is will they level out when sticks are released or do you want them to continue straigth on. Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted March 31, 2017 Share Posted March 31, 2017 Your computation is correct but the starting points may not be: - 30% MAC for each wing is quite far back. 23-25% is safer to start with - the upper wing is in free air and is more effective. The second drawing on the rcgroup thread accounts for that. I would stick to the 30% as on the plan for the first flights. If you have to use weights that you can easily remove to achieve that. The "leads" used to balance Aluminium car wheels are ideal for that. Lucas Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 31, 2017 Author Share Posted March 31, 2017 Without access to a wind tunnel to figure out where the CP actually is, erring on the safe side makes good sense. However if I come out at 35% without ballast I will be well satisfied. Tim Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted April 25, 2017 Author Share Posted April 25, 2017 Had a bit of a break and started off again by having a fiddle with the cockpit and windshield. Windshield not quite as symmetrical as I would like but I guess it will suffice. Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted April 28, 2017 Author Share Posted April 28, 2017 Fuselage covered except for trim lines which will be white just not decided where and how many. Quote Link to comment Share on other sites More sharing options...
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