Danny Fenton Posted November 20, 2009 Share Posted November 20, 2009 Well I thought I fancied a little light relief from my winter scale building (a Brian Taylor Mustang and a Brian taylor Hurricane, both electric with sound are on the bench together). I have always liked the Chipmunk and will one day build an accurate one, but not just yet. I saw Andy Glover flying one of these Black Horse Chippys at the Nationals, in Flying Only and it went really well on just a standard 120 four stroke. It seems this beast is a little rare and there are very few pictures on the forum of one so I had a bit of a struggle justifying the purchase. But having seen it up close I am very pleased with it so far. The front end is a little weak and will need a bit of beefing up, as well as a longer motor mount/box fitting. the pilots are 1/4 scale and this model is slightly over 1/5 so they will have to go, but other than that it looks a great basis for a lovely model. You could easily go to town on this model with detailing, I am not however going to do that as this is for winter flying, nothing more. The model will be built to accept either 6S3P 2300mAh A123 or 5S2P 10,000mAh Lipos ( I have them lying around and ought to use them, before you ask ) Some pics before we get into the build, which by the way will not be starting for a week or so as i have a few things to sort first. The pics: You will see how well the 2 x 5S 5000mAh packs fit in this last shot, the tray for the 18 A123 cells will fit nicely underneath. Giving me the option of either. This model is supposed to weigh 6.4 hg and my field limit is 7kg so we will see how it works out. Black Horse stipulate a 45cc Petrol for this, I am going to use an electric motor of just 1500 watts. Which is around 100watts to the pound, however this is a large model at 85" so I am into new territory here....... Should be fun. Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted November 20, 2009 Share Posted November 20, 2009 Those pilots look too grumpy anyway Danny, hope you find some with a smile on their faces. Looks a great interesting "quick win" to me, not much building for a lot of aeroplane. I'll be watching with great interest. Trust you'll be flying it as soon as the weather breaks? Cheers Chris Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 20, 2009 Author Share Posted November 20, 2009 Chris, what are you saying the pilots are styled on my aged visog...... Its not quite the great deal we had with the Seagull Sea Fury's, this kit is very nearly £300 but as you say alot of aeroplane. It is well designed and clearly flies well in the hands of Andy Glover. I have been through the instruction "leaflet" and lets just say I am glad I have built similar before because the instructions are vague, and the pictures don't appear to refer to the model I am building. Oh well, all adds to the fun I suppose. I am resisting the urge to strip the film off, fill the gaps in the sheeting on the wings, cover it in resin and glass cloth and add oodles of detail........must not detail........must not detail..........must not detail................. Chris is helping me with my 12 step plan, well its only one step really "must not detail" What's wrong with this picture? Now the maths and all mine and Chris's experience say this will work but the common sense in me says how can a little motor like this drag this hulk around............ Answers on a postcard to the mad kilowatt flyers at Greenacres MAC Edited By Danny Fenton on 20/11/2009 23:18:36 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 20, 2009 Author Share Posted November 20, 2009 I couldn't resist balancing the tail on to see how it looks. Am I the only sad soul that does this? Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted November 20, 2009 Share Posted November 20, 2009 This one is big! I know everything is relative, but by my standards this is big! Evidence the photo of it taking up my whole lounge this afternoon. I think its the size of the plane making yr motor look small Danny, You have plenty of power there. Not 45cc worth I grant you, But Andy Glover didnt need that either. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 20, 2009 Share Posted November 20, 2009 Yes it does look a little on the small side eh Danny I am sure 100 WPlb will be just fine for the chippy - but are you sure thats a 1500 watt motor - and if so, is that its limit, or have you ( as I am sure you have ) built in some safety margin here? I would think 1800Watts rating would be closer to the mark for some headroom. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 20, 2009 Author Share Posted November 20, 2009 Hi Timbo, safety margin????.............it has to weigh less than 15lbs to get in weight for our field, therefore 1500 watts max is all it should need....... yes this little gem of a motor is a real powerhouse. I guess what really worries me is is the weight of the motor. I may have a real job getting the cells far enough forward. Bit like your Camel I guess. The original Chipmunk only had 150hp so it should be slow........ I might do a few taxi trials before comitting aviation though, just to be on the safe side..... Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted November 21, 2009 Share Posted November 21, 2009 That's nice Danny and I quite like the pilots too. It'll be nice to have a big scale model that doesn't have the hassle of retracts. I've just electrified the Hangar 9 Pawnee and the 4S pack was tiny inside the fuz to the extent that although the calculations said she would fly fine, even experienced electric flyers took one look and questioned the set-up. Edited By David Ashby - RCME Administrator on 21/11/2009 05:52:13 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 21, 2009 Author Share Posted November 21, 2009 Hi David, Yes during the winter the warbirds are not flyable on our field, the wet ground just plays havoc. Hopefully this will still operate happily even though the wheels are not enormous. One good thing is at 1/5 a scale prop is just 16" I guess the the thing that is causing me doubts about the motor is not the weight calculations, its the power required to evercome the drag from such a big airframe. As Chris has already told me drag increases exponentially with speed, so should be okay, we will see, If it doesn't work I can always fit a bigger motor. how did the Pawnee go? I have a soft spot for the Pawnee despite fhaving been given the honorous task of washing out that hopper, not a pleasant job. Cheers Danny Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted November 21, 2009 Share Posted November 21, 2009 Very well, flew like a nice big low wing Cub, which is what it is of course, but a lot more positive and without the need to co-ordinate rudder in the turns. A nice relaxing model. I would throw in a gratuitous picture but don't want to spoil the thread.... Edited By David Ashby - RCME Administrator on 21/11/2009 11:56:50 Quote Link to comment Share on other sites More sharing options...
Tom Foreman Posted November 21, 2009 Share Posted November 21, 2009 Which motor are you going for Danny? I've just received a nice Turnigy SK5065-270 from Hobby City with matching HV ESC, its equivalvent to a 120 size glow and good for 1800W although voltage wise it will only go up to 29.6v (8s1p Lipo or 10s1p A123). Havn't decided on a model yet, could be a toss up between a YT Spitfire or a Chris Foss Xtra Wot. The whole drive system (Motor + ESC + UBEC + 8s1p 3700 LiPo) weighs 1.3Kg (2.86lb) hopefully enough ballast for either model. Look forward to seeing more of your Chipmunk Cheers, Tom Quote Link to comment Share on other sites More sharing options...
Tom Foreman Posted November 21, 2009 Share Posted November 21, 2009 With regards to power, 1500W might not seem much, but if your running at 85% efficiency compared to 25% for an IC motor then it explains why it needs a 45cc engine if your losing 75% of the power! Tom Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 21, 2009 Author Share Posted November 21, 2009 Hey David please lob a piccy of the Pawnee in lol, it wont spoil the thread Hi Tom, yes IC is mainly noise lol, I have two motors in mind, but the first one I will try is a 4260Xp which is good for 1475 watts on 6S A123. The revs will be a little higher than I like, but I know I wont need to use more than half throttle, so it shouldn't be an issue. Of course I could be completely wrong, and will have to eat my proverbial hat Cheers Danny Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 21, 2009 Share Posted November 21, 2009 Posted by Tom Foreman on 21/11/2009 14:59:03:With regards to power, 1500W might not seem much, but if your running at 85% efficiency compared to 25% for an IC motor then it explains why it needs a 45cc engine if your losing 75% of the power! Tom Thats a very good point Tom Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted November 21, 2009 Share Posted November 21, 2009 I'm really interested in this one as I have a theory that says models get more efficient as they get bigger. So where we'd need 100W/lb with a 3lb model, I think we need less per pound as planes get bigger. Our 10lb plus, Sea Furys go really well on 800W and we only use that to power round huge loops. Most of the time we are well down with the throttle stick. So if this comes out below 15lbs (which it must!) then it should go as well on 1200W. So more than that will be a bonus and used little. Less than that would probably still be fine but more scale like. If a bit less power means a lot less weight, then that is another choice to be made. However, weight might be governed in this one, purely by the need to get the c/g right. Finally don't forget, the 100W/lb rule was around in brushed motor days, and they were hard to get above 60% efficient. We are pretty spoiled these days. Quote Link to comment Share on other sites More sharing options...
Tom Foreman Posted November 21, 2009 Share Posted November 21, 2009 Did you see the Megastar Link a 30lb model flying on 60 - 80 W /lb? Big Prop which can be more efficient, especially with low wing loading like the Easy Star. On a completely different subject, have just run up a 90mm electric ducted fan F22, 1400W for a 2Kg (4.4lb) model (hopefully when finished) gives 320 W / lb Edited By Tom Foreman on 21/11/2009 16:07:22 Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted November 21, 2009 Share Posted November 21, 2009 Posted by Chris Bott on 21/11/2009 15:42:31:I'm really interested in this one as I have a theory that says models get more efficient as they get bigger. So where we'd need 100W/lb with a 3lb model, I think we need less per pound as planes get bigger. Our 10lb plus, Sea Furys go really well on 800W and we only use that to power round huge loops. Most of the time we are well down with the throttle stick. So if this comes out below 15lbs (which it must!) then it should go as well on 1200W. So more than that will be a bonus and used little. Less than that would probably still be fine but more scale like. If a bit less power means a lot less weight, then that is another choice to be made. However, weight might be governed in this one, purely by the need to get the c/g right. Finally don't forget, the 100W/lb rule was around in brushed motor days, and they were hard to get above 60% efficient. We are pretty spoiled these days. I'm sure there's something there Chris, my Tigercat weighs 20lbs and flies like a rocket on 1600 watts, tis a twin mind......Edited By David Ashby - RCME Administrator on 21/11/2009 21:13:53 Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted November 21, 2009 Share Posted November 21, 2009 Ok, you asked for it - one Pawnee pic. Flies nice and scale on the E-flite Power 46, 60amp ESC, 14x6 prop and 4S 3800 Li-Po. About 90 watts/lb, flies 10 mins. Still trying to find a pilot though, if anyone knows where I can get a 1/5 - 1/6th full body pilot? Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 21, 2009 Author Share Posted November 21, 2009 Hi David that looks great. As for pilots figures how are the Dragon BBI figures for scale? They are 1/6 and can be picked up on Ebay for around a tenner. This is the desert pilot I am using in my British P-51 Cheers Danny Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted November 22, 2009 Share Posted November 22, 2009 AH that's great, watching a few items on ebay now. Are the figures very heavy Danny? Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 22, 2009 Author Share Posted November 22, 2009 Hi David, they are a little, the best thing to do if you are keeping an eye on the weight is to substitute the main torso and limbs for foam or balsa. The head, hands and feet are seperate so its easy to fit them to the foam substitutes. There are several different styles, and the price varies considerably. I have a permanent search reminder on EBay that notifies me when a new one is listed. As some are very rare. There is an EBay seller in the UK called Clare, who will split down outfits if you are interested I will ftry and find her E-shop for you and post the link if you are interested? These figures are enough to make me want to only ever build to 1/6 scale PS, I enjoyed the article on the Tigercat, looking forward to the flight report. Chris Bott has a DH88 of a similar size (88") and it goes really well on two 600 watt motors, in fact over powered. Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted November 22, 2009 Share Posted November 22, 2009 Just ordered one Danny, cheers a nude George W Bush with a separate jacket and Mrs A says she can make the trousers. I'll do some surgery when he arrives and the office should then have a bod. Thanks re the Tigercat, right sorry to go off topic - now have you finished and flown that Chippy yet? Edited By David Ashby - RCME Administrator on 22/11/2009 09:01:15 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted November 22, 2009 Author Share Posted November 22, 2009 Lol glad you have a pilot David, no I am not even going to start Chippy until the end of the week. but don't blink or you will miss it, its pretty straight-forward and i am not going to modify very much at all. I have studied and have a plan.............. Keep your eye on Ebay for Dragon clothes, I got a great leather with sheepskin collar flying jacket for a fiver. I also got a good flying suit for a couple of quid that would probably suit your "croppy" off thread? who us?.......... Quote Link to comment Share on other sites More sharing options...
Klippy Posted November 22, 2009 Share Posted November 22, 2009 Watch it lads, all this talk of nude bushes is bound to get moderated.Black horse Chipmunk, there back on topic! Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted December 3, 2009 Author Share Posted December 3, 2009 Nothing in life goes to plan.....I had intended getting this build under way a week ago However have finally managed a little on Chippy. Fitted three fairly hefty servos into the fuselage. It was a very tight fit as the fuselage was a bit narrow There are slightly longer lengths of unsupported piano wire than I would really like but i am trying to build this more or less as per instructions. Anyway the tailwheel/rudder linkage is fairly cunning in its design, however let down in the execution. A piece of piano wire forms the tailwheel and continues up in line with the back of the fin and forms the torque link to operate the rudder. Very clever. This means the tailwheel is a little further forward than scale but does mean no visible horns on the rudder. Those that know the chippy will know that the fin and rudder is only OVER the tailplane so any controls are really prominent. This method hides all that and for the sake of the tailwheel being slightly out. I can live with that. Now the problem with the execution. For this to work properly the piano wire must run pearallel to the fin trailing edge. This then translates to the tailwheel mounting bracket being manufactured at the completely wrong angle. If you bend the piano wire then the hinge will bind up, the line must remain straight. The simple solution was to make a packing piece of light balsa for the bracket. Okay If i can find a little time this evening I will try and do a bit more...... Cheers Danny Quote Link to comment Share on other sites More sharing options...
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