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Q-talk 85 - Q-list Connections

Question:

Ted Kibiuk # 508
Holland Patent, NY

In storage, a peculiar problem again has surfaced and I do not know how to remedy it. On the leading edge of the canard I’ve noticed many indentations. It’s as though a sharp edged tool was hammered down the surface. These indentations are about 6”-8” apart, 1”-2” long and about 1/8” deep. The layered expoxied fiberglass seems to have been sucked down. Don’t know how this is possible! The foam beneath this could have shrunk, making these indentations. I wrote to Ron Alexander about this. He suggested I fill the indentations with an epoxy slurry mix, sand to the adjoining surface and then place another fiberglass layer over all of this. A lot of work, but worth doing.

Response Summary:

This question resulted in responses from the QLIST including one very civil response from Jim Masal! There was a general concern for the leading edge because that area does add to the torsional strength of the canard. Masal stated that he had never seen this symptom on plans-built canard before and that a good close-up photo of the problem area would help. It sounded to most members that the damage is likely mechanical in nature by something being forced into the leading edge of the canard. The suggestions included:

  • Fix the canard per the suggestion from Ron Alexander and then load test the canard to be sure of its strength.
  • Drill a few 1/16” or smaller holes around the parameter of the indentation and inject a thin micro slurry into one of the holes to see if the slurry oozes out of any of the other drilled holes indicating a void behind the indentation. Watch for any exotherms on the slurry because the heat could not escape and be sure you have a tight fit where you inject the slurry.
  • There was a concern that nonstandard filler material was used like a polyester resin where uncured material could have seeped through pinholes in the glass making a cavity in the foam beneath.
  • Sand back an area of about two inches around the indentation in all directions removing all paint, primer and filler. Once down to the glass, you can look for damaged glass. Wetting the sanded glass with water will help temporarily reveal the glass structure below. If you decide to replace the glass, consult the plans to be sure you understand and follow the glass schedule and directions. Standard practices include sanding out the damaged glass at an angle that would provide for 1 inch out from the center per ply. Then lay up patches in the original order and sequence followed by the final bid and peal ply.
  • The original text of the responses will be mailed to Ted for his review and consideration. These responses are only based on the description of the problem above and may not resolve the issue. In any event, the leading edge of the canard is a very important component of the Quickie design.


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