Trundle

Ive only ever seen scale turbojets and turboprops

Has anyone seen/built/flown a scale turbofan?

If not why doesn't someone build one? They are more efficient produce more power and are lighter than their fuel-guzzling turbojet counterparts. High bypass scale turbofans would look awesome on a scale airliner but I think there would be a lot of benefits even with a low bypass turbofan.

WrenTurbines

Eddie Weeks and Mike Burlington have tried it, see

http://www.rcuniverse.com/forum/m_26.../tm.htm#262925

It's not easy. One of the big problems is that on a turbofan the two shafts run one inside the other. That's not so difficult for a fullsize engine but very difficult to do on a miniature turbine where the shaft is usually less than an inch in diameter. See here for good pictures of the layout and information about turbofans, showing some of the reasons why it is so difficult to miniaturise.

http://en.wikipedia.org/wiki/Turbofan

Sara Parish
Wren Turbines

EddieWeeks

The one I made has two different shafts turning different directions, and its basically a bolt on unit.

Sometimes referred to as an aft fan. If anyone wants it they can buy the whole thing from me for $800.

I never finished it, but I am confident it would have worked well with enough cooling to the rear bearings.

Eddie Weeks
http://www.variablepitchhobbies.com/