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Repairing foam blades
| Instructions how to repair broken foam blades. Flying with repaired blades can be dangerous. Take appropriate precautions. |
Introduction
Foam blades break easily. That's a bad thing but also a good thing, because otherwise something more expensive might break.
They are cheap, but not that cheap...
While waiting for a spare parts shipment that was held in customs, I noticed that foam blades broken at the blade root are surprisingly easy to repair:
- Cut off the broken end
- Drill a new hole
- Glue the GFK disks to both sides
- Squeeze flat
- Balance, attach and fly!
Below a cut through a blade that was beyond repair. A soft foam core is surrounded by a harder plastic shell.
 |
Step-by-step instructions
Cut off the blade end
Stack both blades, align the blade tips and cut both at the same time with a knife.| There are two types of foam blades: symmetric and asymmetric. They have almost the same shape, but the difference can be noticed at this step. |
Remove remaining blade material from the GFK disks
This is a bit of work, but straightforward: Cut off the plastic material from the GFK disk, so that no white plastic remains on the yellow GFK. Don't be shy with the knife, the GFK material is pretty tough.
Mark hole location
- Insert the blade end into the blade mount on the rotorhead
- Leave 1 mm space, so that the blade can swing back- and forwards
- Mark the location of the hole with a 2 mm drill
Drill hole
Again, stack both blades on top of each other. Drill a 2 mm hole.Glue GFK disks
Use the back end of the 2 mm drill to guide the GFK disks.The side that was glued previously should again face to the inside, otherwise the blade won't turn as smoothly.
Remove the drill.
It may be a good idea to add some more glue from the outside.
| Note: Cyanacrylate glue will dissolve the foam core of the blade. In particular, do not try to seal the back end of the blade with CA glue |
Cut edges
The edges are rounded, as shown.
The circled area is important: When the blade hits an obstacle, it allows it to swing back in the blade mount, preventing damage to the rotorhead.
Blade thickness
The blade needs to be squeezed a bit, so that it fits into the blade mount, and can move easily.
Balance blades
Balance as usual.  Instructions |
Do they break?
Since the blades are now thicker at the blade root, will they still break on impact, or damage the rotorhead instead?I had one incident where the heli went into the ground at 30 degrees angle. The blades broke off cleanly, no other damage resulted.
One remaining question for a rainy weekend: Could I fix them a 2nd time, they are getting shorter and shorter...
© Markus Nentwig 2007-2008
The content of this page is provided without any warranty and may not be reproduced without permission.