kc Posted July 16, 2021 Share Posted July 16, 2021 It is normal to consider ounces per square foot. so the sq inches should be divided by 144. Therefore if the weight is 176 ounces that makes it about 34.4 oz per sq ft. Pretty high! Quote Link to comment Share on other sites More sharing options...
Don Fry Posted July 16, 2021 Share Posted July 16, 2021 Convention, a glow motor set up is weighed with an empty tank. I don’t think I would much fancy a 10.5 to 11 lb model on a 60 2 stroke, plus 8 oz for fuel, and then try to fly it as a spotter look alike, benign wing form or no benign wing form. And a lot of work to find out. Quote Link to comment Share on other sites More sharing options...
eflightray Posted July 16, 2021 Share Posted July 16, 2021 Found this -- https://www.youtube.com/watch?v=Ho5QhjOql6A Ray Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 16, 2021 Share Posted July 16, 2021 Wing loading for models is usually expressed as oz/sq ft (or gms/sq dm). Your figures come out at 34.43oz/sq ft. Quote Link to comment Share on other sites More sharing options...
eflightray Posted July 16, 2021 Share Posted July 16, 2021 (edited) Wing loading, 34 oz/sq.ft eeek! My B-25 Mitchell is scratch built in balsa. 93" span. 9lb 11oz including 6s battery. 20 oz/sq.ft Flies on 60 watts/pound Admittedly it's four woops, twin props, but I'm sure the Optica (92.5" span) could fly with a single prop on not much more power. Just keep the weight down. P.S. my B-25 first flew in June '93, and I still have her. Ray The picture was from quite few year ago, the plane looks the same though ? Edited July 16, 2021 by eflightray Quote Link to comment Share on other sites More sharing options...
Dad_flyer Posted July 16, 2021 Share Posted July 16, 2021 10 hours ago, Basil said: The wing measures 2 wings @ 32" x 11 1/2", (736 sq "). That is only 72" (+fuselage width) wingspan? I thought this was a 90"+ plan. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 16, 2021 Share Posted July 16, 2021 (edited) Basil Wing loading is normally quoted as oz/sqft so the wing area 736 is divided by 144 = 5.1 sqft Wing loading is thus 176/5.1 = 34 oz/sgft. That figure is well into the 'sport' class plane wing loading rather than a slow flyer (or glider) where a wing loading could be as low as 10 oz/sqft according to this site. 72"? Are you omitting the centre section? The wing area normally includes the full span so 92 x 11.5 = 1058 sq" or 7.3 sqft. That gives a loading of 176/7.3 = 24 oz/sqft. Even so still no slow flyer. Edited July 16, 2021 by Simon Chaddock Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 16, 2021 Share Posted July 16, 2021 Sarik give the span as 92.5" making the scale aprox 1/5 therefore the wing area should be 1/25 of full size, which according to Wiki is 170.5 sq ft, making the model's area 6.82sq ft. At a weight of 176oz wing loading should be 25.8oz sq ft. High but not spectacularly so. Quote Link to comment Share on other sites More sharing options...
Basil Posted July 17, 2021 Author Share Posted July 17, 2021 9 hours ago, Simon Chaddock said: Basil Wing loading is normally quoted as oz/sqft so the wing area 736 is divided by 144 = 5.1 sqft Wing loading is thus 176/5.1 = 34 oz/sgft. That figure is well into the 'sport' class plane wing loading rather than a slow flyer (or glider) where a wing loading could be as low as 10 oz/sqft according to this site. 72"? Are you omitting the centre section? The wing area normally includes the full span so 92 x 11.5 = 1058 sq" or 7.3 sqft. That gives a loading of 176/7.3 = 24 oz/sqft. Even so still no slow flyer. Simon, yes I omitted the centre section. The measurement given by me were for the wing asy as given on the plan. There is the fuse section between them @ some 29", this includes two wing stub(Wing proper) @ 7 1/2". Bas Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 17, 2021 Share Posted July 17, 2021 It could be argued that the full size Optica is not really a slow flyer. 260 hp. Max weight 2900 lbs. Wing area 170 sq ft gives a wing loading of 17 lbs/sqft. By comparison some true slow fliers. Piper Super Cub (Similar wing area but 40% lighter) 150 hp. Max weight 1750 lbs. Wing area 178 sq ft gives a wing loading of 9.8 lbs/sqft. Fieseler Storch (Similar weight and power but 60% more wing area) 240 hp. Max Weight 2920 lbs. Wing area 280 sqft gives a wing loading of 10.4 lbs/sqft. Not a recognized slow flyer Cessna 172 160 hp. Max weight 2450 lbs. Wing area 174 sq ft. gives wing loading of 14 lbs/sqft. Just saying. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 17, 2021 Share Posted July 17, 2021 Doesn't wing loading take the tailplane into account as this also provides lift? I don't know the answer, just wondered. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted July 17, 2021 Share Posted July 17, 2021 Yes Simon, and it’s loiter speed is not many units above the stall speed, and on a three seater the pilot, loitering near stall, is in an outer seat, rather than in the middle, so he’s temped to do some of the observation work load as well. And it was sold as a a low speed observation aircraft. Complicated way to do a poor job. Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 17, 2021 Share Posted July 17, 2021 59 minutes ago, Gary Manuel said: Doesn't wing loading take the tailplane into account as this also provides lift? I don't know the answer, just wondered. Disregarding tandem wing etc layouts, the tailplane's function is to maintain the mainplane's (AKA wings') required angle of attack. Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 17, 2021 Share Posted July 17, 2021 1 hour ago, Simon Chaddock said: It could be argued that the full size Optica is not really a slow flyer. 260 hp. Max weight 2900 lbs. Wing area 170 sq ft gives a wing loading of 17 lbs/sqft. By comparison some true slow fliers. Piper Super Cub (Similar wing area but 40% lighter) 150 hp. Max weight 1750 lbs. Wing area 178 sq ft gives a wing loading of 9.8 lbs/sqft. Fieseler Storch (Similar weight and power but 60% more wing area) 240 hp. Max Weight 2920 lbs. Wing area 280 sqft gives a wing loading of 10.4 lbs/sqft. Not a recognized slow flyer Cessna 172 160 hp. Max weight 2450 lbs. Wing area 174 sq ft. gives wing loading of 14 lbs/sqft. Just saying. I had similar thoughts to Simon & came to the same conclusion. I've added the Optica's data from Wiki to an existing spreadsheet showing a selection of light & pre WW2 aircraft that could probably be built as models to the scale weight & power as the full size. Scale data.xls Note : I've adjusted the common scale to suit the 93" span Optica. The true scale weight(s) & power for the Optica are, IMO impractical. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 17, 2021 Share Posted July 17, 2021 1 hour ago, PatMc said: Disregarding tandem wing etc layouts, the tailplane's function is to maintain the mainplane's (AKA wings') required angle of attack. Thinking about it, you are right. If the aeroplane is slightly nose heavy as most are, the tailplane would actually be pushing the tail downwards to keep the nose up. Quote Link to comment Share on other sites More sharing options...
kc Posted July 17, 2021 Share Posted July 17, 2021 The original article and plan in RC Scale Aircraft Quarterly 1988 Winter clearly state the wingspan as 81.5 inches, so I don't know why Sarik who were not the original publishers ( that was Argus/ MAP) should now state it's 92.5 inches! It would appear to be an error unless someone measures the actual plan they supply and find it is actually 92.5. Quote Link to comment Share on other sites More sharing options...
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