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Edgly Optica


Basil
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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

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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. 

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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.

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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

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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.

  

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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.

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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

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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

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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.........

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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

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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

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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.

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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

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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. 

 

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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.

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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

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