ericrw Posted October 23, 2015 Share Posted October 23, 2015 What size would a two bladed prop would be the equivalent to a four bladed 16x6 prop ? Would the two bladed prop increase/decrease the speed of the model; foam Mustang P51D 1600mm ws ?? Please advise ! Quote Link to comment Share on other sites More sharing options...
Stevo Posted October 23, 2015 Share Posted October 23, 2015 Are you sure you mean a 16x6 prop... Quote Link to comment Share on other sites More sharing options...
PatMc Posted October 23, 2015 Share Posted October 23, 2015 A 19x6 two blade prop of the same "family" as the four blade [i.e. similar blade shape, thickness etc] should give about the same rpm, therefore power. It will probably be a bit more efficient so may increase the speed & rate of climb. Quote Link to comment Share on other sites More sharing options...
Stevo Posted October 23, 2015 Share Posted October 23, 2015 I' love to see a 19x6 prop on a 1600mm Mustang Pat... Quote Link to comment Share on other sites More sharing options...
PatMc Posted October 23, 2015 Share Posted October 23, 2015 Steve, I was surprised when the OP mentioned a 16" prop on a 1600mm Mustang but a 19" prop would actually be near enough the correct scale size. Quote Link to comment Share on other sites More sharing options...
Stevo Posted October 23, 2015 Share Posted October 23, 2015 Well you do have a point Pat 👍 Quote Link to comment Share on other sites More sharing options...
Josip Vrandecic -Mes Posted October 23, 2015 Share Posted October 23, 2015 Hello Dear Eric , First of all I give you greetings from the Adriatic Sea....and now small contribution from me: Propeller design theory says: 2 to 3 blades, reduce diameter by 10%, 2 to 4 blades reduce diameter by 15%, pitch stays the same in both cases. .....................AND VICE VERSA... Cheers Jo Quote Link to comment Share on other sites More sharing options...
cymaz Posted October 24, 2015 Share Posted October 24, 2015 This may help Quote Link to comment Share on other sites More sharing options...
ericrw Posted October 24, 2015 Author Share Posted October 24, 2015 The four bladed, 16x6 prop, is the stock prop, as provided in the kit. If I reduce the diameter, as suggested by Josip, for a two bladed prop, what effect would it have when flying the model ?? Quote Link to comment Share on other sites More sharing options...
Geoff S Posted October 24, 2015 Share Posted October 24, 2015 2 bladed props are more efficient (in fact 1 bladed props are the most efficient and IIRC are used on control line speed models for that reason). I had problems with the 4 bladed prop on my HK Mk24 Spitfire because it tended to nose over on landing and tended to break the prop even at low speed. I fitted a higher kv motor and sawed off a couple of blades to solve it Actually I also packed retract mechanism so the undercarriage legs were a bit further forward which stopped most of the nose over difficulties. But 2 bladed props can move out of the way whereas there's always a blade near the ground if there are more of them. Geoff Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted October 24, 2015 Share Posted October 24, 2015 Posted by ericrw on 24/10/2015 12:19:08: The four bladed, 16x6 prop, is the stock prop, as provided in the kit. If I reduce the diameter, as suggested by Josip, for a two bladed prop, what effect would it have when flying the model ?? I think you are misreading Josip's post eric - to go from 4-blade to 2 blade you would need to increase the prop diameter not decrease! Josip is talking about going the otherway - ie from a two blade to a 4 blade. So as Pat suggests a 19" of the same diameter would be about equivalent. But I'd check very carefully that you have enough ground clearance for a 19" prop before buying. BEB Quote Link to comment Share on other sites More sharing options...
ericrw Posted October 24, 2015 Author Share Posted October 24, 2015 Thanks BEB , I would like to know what too expect of the flight characteristics, if I did use a two bladed prop. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted October 24, 2015 Share Posted October 24, 2015 If you can fit the equivalent then it won't make a lot of difference. The model might seem a little more powerful because the two-blader is more efficient than the four-blade prop, so slightly higher top speed maybe, a bit more lively in the climb possibly and the verticals might be a bit stronger. But it will be marginal, to be honest I'd be surprised if you noticed much difference. BEB Quote Link to comment Share on other sites More sharing options...
Owdlad Posted March 24, 2016 Share Posted March 24, 2016 Hi folks, quick question? If the recomend prop size is 14x10 but I've only got enough ground clearance for an 11" possibly 12" dia at a push. What pitch should I go up to? 11x14 or 12x13 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 24, 2016 Share Posted March 24, 2016 Owdlad In principle a prop with a pitch greater than its diameter is moving into the realms of the prop stalling when static which can make the take off run rather long before it gets up to flying speed. A few more details would help. What is the motor? IC or electric? What is the plane? Why is your ground clearance much less than the recommended prop? Quote Link to comment Share on other sites More sharing options...
Owdlad Posted March 25, 2016 Share Posted March 25, 2016 Sorry in my haste I'd forgotten to add some details. The engine is a webra 80 Long Stroke pumped & piped The model is a Pb Tornado fitted with retracts. I have shortened the main legs as much as i can but without major surgery I cannot lengthen the nose leg. The joys if inexperience springs to mind Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted March 25, 2016 Share Posted March 25, 2016 My Tornado ran a 12*10 on an OS61SF and pipe, that cuts the grass on anything but a freshly mown strip. It's also not short of power once it gets rolling, but it is slow to accelerate a) because the pipe is hindering it at ground rpm, b) that high pitch prop probably is stalled below flying speed in any case. Quote Link to comment Share on other sites More sharing options...
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