Basil Posted July 12, 2021 Share Posted July 12, 2021 Sarik are advertising a complete kit for this Edgley Optoca ( By John Wright) build. I bought a plan some time ago but already have to much to do on existing builds. I have brought this model to poeples attention before but had little response. My thinking is that if Sarik are making a kit they have had enquiries in numbers. Has anybody bought the kit or built one? It would be interesting to hear from them. Over to you folks. Bas Quote Link to comment Share on other sites More sharing options...
Maurice Dyer Posted July 12, 2021 Share Posted July 12, 2021 Not made one Basil, but always thought it would make an interesting model. I don't know, but it's crying out for a big electric dusted fan . Does somebody make one big enough ? Not dabbled on edf before. Cheers Maurice Quote Link to comment Share on other sites More sharing options...
Basil Posted July 12, 2021 Author Share Posted July 12, 2021 I think that has been said before!!!! But I think the same, after all that's all it is(Eh!!!!!! Thats all it is !!, said simply) If Sarik make a kit then there must be a demand, but from whom??? Bas Quote Link to comment Share on other sites More sharing options...
Don Fry Posted July 12, 2021 Share Posted July 12, 2021 Aaarrr, but I’ve always suspected, we buy plans, as a lady buys a handbag. And a Sarik short kit is the things what goes in the virtual handbag. The demand would cease if you were made to use it, or build it, as the case might be. 1 Quote Link to comment Share on other sites More sharing options...
PeterF Posted July 12, 2021 Share Posted July 12, 2021 7 hours ago, Maurice Dyer said: Not made one Basil, but always thought it would make an interesting model. I don't know, but it's crying out for a big electric dusted fan . Does somebody make one big enough ? Not dabbled on edf before. Cheers Maurice Looking at the one plan section on the Sarik Hobbies website, the duct diameter is 11 inches, this does not need a ducted fan but a ducted propeller. Given it needs a 60 size glow engine and a 250mm EDF is rated at 15 to 40 kW with 55kg of thrust an EDF would be overkill. The cost would also be prohibitive and a waste if run at low power to suit the model. Quote Link to comment Share on other sites More sharing options...
Outrunner Posted July 13, 2021 Share Posted July 13, 2021 15 to 40kW and 55kg of thrust, in a model. The mind boggles? Quote Link to comment Share on other sites More sharing options...
Basil Posted July 13, 2021 Author Share Posted July 13, 2021 (edited) PeterF, yes it uses a ducted prop, on a glow engine. My interest is in an electric conversion, but I dont fully understand all the criterior involved that allows me to calculate( Speculate) on the motor/prop combinations, bearing in mind that certain dimensions are dictated to by the design. I dont know anything about ducted fans. Cant you use a more appropriate sized fan rather than fitting the fan to the space, just fit a smaller fan. Surely it does not need to fill the space entirely. Or does extra space around the fan negatise or adversly effect the fans performance. Why oh why has seemingly no one has built it, or will own up to that fact.!!!!! Bas Edited July 13, 2021 by Basil addition Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 13, 2021 Share Posted July 13, 2021 When does a multi blade ducted prop become a ducted fan? The full size Optica uses a 5 bladed fan. There are also 5 bladed props. There is no reason why an 11" ducted anything has to consume or even be capable of consuming 15 to 40 kW. It is just an issue of finding a suitable motor/fan or prop combination to fit the available space. Basil To answer your question it might be useful to find out the Watts used to drive an 11" prop or better still an 11" multiblade if you can find one and then compare that to the power from the equivalent glow. Remember most RC planes do not need the direct scale equivalent of a full size prop. How many RC P51 Mustangs manage nicely on a 2 blade and with a reduced diameter at that. The props used on larger quads might be a good source. Quote Link to comment Share on other sites More sharing options...
Basil Posted July 13, 2021 Author Share Posted July 13, 2021 There are some 3 bladed available.11x6/7/&8.'Mastercrew' On 4max, brushless, 3535-1390 ,11x5.5, 2s. I have emailed them for guidance. bas Quote Link to comment Share on other sites More sharing options...
kc Posted July 13, 2021 Share Posted July 13, 2021 You asked " Why oh why has seemingly no one has built it, or will own up to that fact.!!!!! " and the answer is probably that it's the most difficult type of model to build! I think I mentioned in another thread that I knew of a most experienced aeromodeller in Australia who started this model but as far as I know encountered so many problems making a proper scale model that he ( probably) gave up. Obviously it's not an impossible model as the original designer proved but it clearly difficult to hide all the gear and make a practical yet scale model. Before you order cut parts make sure the huge canopy is also still available. Quote Link to comment Share on other sites More sharing options...
Basil Posted July 13, 2021 Author Share Posted July 13, 2021 Hi KC, I have to much on to start yet another!!!!!!. Exploring more for the future. Yes you are correct in thinking that. I have a copy of the plans and in my estimation is not without its problems, even that of size!. I think we have spoken before about this. I like to shake the tree occasionaly and see what falls out.Just dont understand why Sarik would contemplate any investment without some interest especailly offering a full kit, with canopies etc . Bas Quote Link to comment Share on other sites More sharing options...
Basil Posted July 13, 2021 Author Share Posted July 13, 2021 Just heard back from George re electrification. He suggestes; 5055-595, 11x6 3bld, 6s 4500 lipo. Provides 705 lbs of thrust, speed 60 mph. I think the top speed is misleading as its supposed to be a spotter plane used instead of a chopper. In my book that means SLOW flight. Bas Quote Link to comment Share on other sites More sharing options...
Brian Lambert Posted July 13, 2021 Share Posted July 13, 2021 (edited) 3 hours ago, Basil said: Provides 705 lbs of thrust You could lift a Mini with that, or at least make it go very fast. Edited July 13, 2021 by Brian Lambert After thought. 1 Quote Link to comment Share on other sites More sharing options...
Matt Carlton Posted July 14, 2021 Share Posted July 14, 2021 Would it be possible to mount two 3 bladed props to make, in effect, a six bladed prop. Use a low pitch like 11 x 4 to keep the flying speed down but the thrust high? Quote Link to comment Share on other sites More sharing options...
kc Posted July 14, 2021 Share Posted July 14, 2021 The big problem is likely to be how you could fit the Lipo in at the position for correct CG and be able to change it without ruining the scale appearance. A rough mock up might prove whether this is possible or impossible without the expense of buying the kit......... Quote Link to comment Share on other sites More sharing options...
eflightray Posted July 14, 2021 Share Posted July 14, 2021 Built light it should be ideal for EDP, especially as a relatively slow observation plane, FPV ? I once considering a scratch built one using an old helicopter bubble canopy. Ray. (my avatar is a twin EDP, 6" props) Quote Link to comment Share on other sites More sharing options...
Basil Posted July 14, 2021 Author Share Posted July 14, 2021 KC, yes that thought did occur to me, a 6s lipo of that size weighs 635grms, all in the cockpit I would imagine!!!!.That would equate to a fuel wt of a similar amount. What does say a tank+ fuel weigh for a 60 engine.?I've just had a quick look at the paln, bit confusing.You could at the very least get the lipo near the CG. In the leading first quarter perhaps. I think the motor is oversize if so ,use a smaller lipo does help. BAS Quote Link to comment Share on other sites More sharing options...
Basil Posted July 14, 2021 Author Share Posted July 14, 2021 7 hours ago, Matt Carlton said: Would it be possible to mount two 3 bladed props to make, in effect, a six bladed prop. Use a low pitch like 11 x 4 to keep the flying speed down but the thrust high? matt, surely there's not enough room on the spindle for 2 props!!!! bas Quote Link to comment Share on other sites More sharing options...
Basil Posted July 14, 2021 Author Share Posted July 14, 2021 Sorry folks a mis type as pointed out by Brian. its 7.5 ibs of thrust not 750. Very Very sorry, I consider my wrists well a trully slapped. Then again I might like it. Keep it clean folks. bas Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 14, 2021 Share Posted July 14, 2021 I am struggling to find a picture of a built Sarik Optica. Even their web site only shows a picture of the full size. It appears John Wright took some scale liberties as his engine is mounted as a pusher so there is no 'afterbody' in the duct which on the full size actually holds the flat 6 Lycoming thus on the full size the fan is in a tractor arrangement. Apart from adding another layer of construction complexity there is no reason with electric power why a true scale layout could not be used although the battery would probably have to be placed across the canopy under the seats to achieve a workable CofG. Quote Link to comment Share on other sites More sharing options...
Basil Posted July 15, 2021 Author Share Posted July 15, 2021 Simon, I have a copy of 'Scale aircraft' dated winter 1988!!!!.The front page features 5 AC's in line in the air. Inside is a 2 page article by John Wright with a picture of him holding the finished model. You cant see any detail. The plans from sarik lack detail of the engine and its mounting, so cant draw any conclusions about that I would have thought that given the size of the leccy motor and the Lipo's that achieveing the CG would be diffult. I am no expert, just the opposite in fact. Bas Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 15, 2021 Share Posted July 15, 2021 Basil The Optica is aerodynamically quite an efficient airframe so with an idea of its likely all up weight you could establish a reasonably accurate figure for the Watts required to fly it. The Sarik web site, or anywhere else come to that, makes no mention of its weight only the wing span and that it uses a 61 engine. There is a a post in the RC Universe website by someone seeking help to build the 81.5 " span version, also designed by John Wright, that had removeable foam outer wing panels. Dated April 2007 the post was viewed 624 times but had zero replies! It would appear the John Wright Optica has never been a popular build. I do have several ducted prop planes as well as true EDFs but nothing comparable to the size of your Optica. Quote Link to comment Share on other sites More sharing options...
kc Posted July 15, 2021 Share Posted July 15, 2021 Well the post on RC Universe was the person from Australia who I mentioned earlier as you can see he had many replies including some from me ( I am kdc ) and I had lots of email correspondence from him too on many aeromodelling topics. Eventually the correspondence dried up and I think he had sidelined the project or perhaps abandoned it after a couple of years. So it would seem even an expert builder probably gave up on this design which should give you some pause for thought before you too start this plane! Back in 2007 this design was in the RCME etc Plans Service and only years later did Sarik Hobbies take over the plan with all the other RCME etc plans. Quote Link to comment Share on other sites More sharing options...
Basil Posted July 16, 2021 Author Share Posted July 16, 2021 Simon, in addition to the 2 pages found there is a continuation of another 2 pages, descibing the build. It is said to wiegh 11 lbs,( 10.5 with built up rather than foam wings). This is with the 60 engine and presume a full tank of gas.In its favour is the high aspect wing ratio. You are obviously well versed in electric formulea so I look foorward to you input.John Wright does make the comment that he had a 60 that he wanted to use(Giving the impression that it was oversize) and this made the plane rather fast at the top end.I will send you a PM. Bas Quote Link to comment Share on other sites More sharing options...
Basil Posted July 16, 2021 Author Share Posted July 16, 2021 (edited) The wing measures 2 wings @ 32" x 11 1/2", (736 sq "). 176 ozs ,div by 736 =0.239 ozs / inch sq!!!. Is that correct. How does this compare. Is that how its worked out. Bas Edited July 16, 2021 by Basil Quote Link to comment Share on other sites More sharing options...
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