How to retrofit a Ducted Fan Engine for Propeller Use
04-01-2006, 11:35 PM
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How to retrofit a Ducted Fan Engine for Propeller Use
Ok I know it has been done but I have never seen one. What is the techinique for useing a ducted fan for use with propellers. What engines can be use, what pipes, what props, what airframes, etc. I already know the ducted fans engines pull in the 20,000+ range and require small propellers. Someone who uses this setup could share with the rest of us. I hear that they will pull a sleek plane very fast
04-02-2006, 01:41 AM
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RE: How to retrofit a Ducted Fan Engine for Propeller Use
They are ported completely wrong to turn a useful sized prop. Plus the crankshaft is probaby too short. Why would you do it anyway when you can get an engine made to do it in the first place?
04-02-2006, 06:51 AM
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RE: How to retrofit a Ducted Fan Engine for Propeller Use
Hello,
you should ask in the "Extreme Speed Prop Planes" forum. These guys know their job.[sm=biggrin.gif]
you should ask in the "Extreme Speed Prop Planes" forum. These guys know their job.[sm=biggrin.gif]
04-02-2006, 07:40 AM
#4
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RE: How to retrofit a Ducted Fan Engine for Propeller Use
Buzz,
Engines originally intended to power a 5" diameter ducted, are timed to be at their best between 21,000-25,000 RPM.
As such, propping such an engine to spin more slowly, to observe the prop manufacturers' RPM limits (and to prevent the risk of a 'grenaded' prop...), would be using a thinner part of this engine's power curve. Wasted performance potential.
On the other hand, propping them to spin at their original RPM, would require an F-1 type pylon racing prop.
These are available only for .40 engines and are the only GFN props that would endure this RPM.
Normal .40 size C/F props, like from Bolly, would serve the same purpose and would properly load a .91 sized D/F engine, for its intended RPM, without breaking up for sure (not guaranteed not to break up at 23-25K, but the risk of it happeneng is lower).
Engines originally intended to power a 5" diameter ducted, are timed to be at their best between 21,000-25,000 RPM.
As such, propping such an engine to spin more slowly, to observe the prop manufacturers' RPM limits (and to prevent the risk of a 'grenaded' prop...), would be using a thinner part of this engine's power curve. Wasted performance potential.
On the other hand, propping them to spin at their original RPM, would require an F-1 type pylon racing prop.
These are available only for .40 engines and are the only GFN props that would endure this RPM.
Normal .40 size C/F props, like from Bolly, would serve the same purpose and would properly load a .91 sized D/F engine, for its intended RPM, without breaking up for sure (not guaranteed not to break up at 23-25K, but the risk of it happeneng is lower).
