I have a TechOne SU-27 flat foamie with a 64mm edf.
The edf housing is only attached to the airframe at two points.
At a specific rpm the edf housing resonates badly and contacts the impeller.

I'm tempted to cut out a couple light ply ring segments to glue to housing.

Am I on the right path?

Is this a common issue?

Thanks,
Eric

Just sounds like your fan in unbalanced....pretty common especially if its a stock unit. A lot of my edfs will resonate at a certain RPM, but usually goes away when I exceed or decelerate.

Try and rotate the impeller a few degrees on the shaft at a time, recheck untill you hit the sweet spot

If you can remove the motor fan unit, I offer dynamic balancing services for a fee. It will run very smooth afterwards.

Don

Thanks for the advice.
I did balance the impeller.
In this case i can actually watch the the housing deflect inward towards the impeller at a specific RPM.
Any other ideas?

If it is your shroud defleting. Get ahold of some CF strands/tape/mesh and epoxy this around the shroud to beef it up.
Take a look at how guys use the CF tow strips to beef up the glassed intakes. same method same purpose.