Could you please settle an argument for me. I say that a FOD guard on a turbine does not have a detrimental effect on thrust/power but a friend of mine insists it does. Anyone with experience of using one please reply.

Stu,
your right.
It does not have a detrimental effect on thrust/power, tell your friend to keep flying props.
CZ

That's the best laugh I have had all day....too funny!

Your friend MAY be thinking of ducted fans and applying the same theory to turbines. The inlet of turbine is a low pressure zone and hence a FOD screen has minimum to no effect on our models. I flew my HS with and without FOD screen and recorded almost identical top speeds at Fresno jet meet last year!

I can't comment on model turbines, however, fod screens are used on some full size applications and they do make a difference. Two examples i can think of off the top are the A-37 jet fighter made by Cessna and the HH53 chopper. In the case of the A-37 the screens are retractable.

One thing that you guys might be overlooking is the size of the mesh of the screen. A mesh size of 1/16 inch will probably not cause any degradation in airflow-OTOH a mesh size of 1/32 or smaller would. I have seen some tea strainers tha use a very small mesh size (between 1/64 and 1/32 inch). Only sure way is to test it with and without. Scott

I have experience on 2 types which have FOD screens and both suffer around 8% degredation when they are used. One is the A37 Dragonfly (which has retractable screens) and the other is the S61 helicopter. The ones on the A37 are linked to the undercarriage and cover the inlets when the gear is lowered and there is weight on the wheels. (You can also lower them manually i.e. before a strafing pass). The S61 had FOD guards fitted for summer use only as they can ice up in the winter (as can those on the A37). Hope that this helps!

So what do you guys make the screen from, I have a wren wm54 and have been thinking of making a mesh cover of some sorts!!!
Any ideas would be appreciated.....

Lee

Lee 999
Check this recent thread on the subject.
Johnny

http://www.rcuniverse.com/showthread...893&forumid=26]

. . . so long as the open area of the mesh is greater than the max aperture of the intake?

Pilots,
Yes- I would say it does have a definite effect on a model gas turbine - because the first time you ingest some FOD in your engine because you ran it without a screen - the thrust WILL be degraded and so will your bank account (if enough gets sucked in there).......moral of story - use SOME kind of screen to protect your engine....JMHO

Jackjet

It can ruin your day if the screen ices up.

Stu,
your right.
It does not have a detrimental effect on thrust/power, tell your friend to keep flying props.
CZ

We call them "bug smashers" in the land down under

and yes i do still enjoy flying bug smashers too....