DLG Wing Repair

Using a Local Vacuum Bag

by Jay Decker

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Ever been doing something for awhile, so long that you consider it 'Old Hat', but then have someone tell you that they have never seen that technique and that you should share it? Well, here's how I've been fixing delamination damage and failures on bagged wings for sometime.

The Taboo wing shown in the photos below had severe delamination damage on the top and bottom of the wing, including separation of the carbon fiber (CF) spar caps (top and bottom) from the foam core.

Note: The photos below were all taken after the resin had cured, since I didn't have an extra set of hands to take photos while performing the repair. So, I was not able to capture more details in photos.

Repair

14 mil Mylar applied over the repair area.

There is another piece of Mylar covering

a repair area on the bottom side of the wing.

  • Resin was injected underneath the delaminated CF spar caps and FG skins using a syringe with a needle.

  • There were some small compressions dents and cracks in the foam from the crash damage. Theses voids in the foam were filled with resin and fumed silica (cab-o-sil); some FG was removed to allow the voids to be filled.. These voids were small; if the voids would have been larger, microballons would have instead of cab-o-sil for a filler to save weight.

  • Patches of new glass were applied over cracked and broken areas in the FG skins, wet with resin and excess resin was blotted up with paper towel. A thin smear of resin and cab-o-sil was placed on the new glass to keep resin from being sucked out of the repaired area by the vacuum.

  • After the repairs were applied, a piece of 14 mil (0.014" thick) bagging Mylar was placed over the repair area to impart a smooth finish to the repair. The Mylar was held in place with transparent tape.

Vacuum Bag

  • Paper towel was placed above and below the wing in the area of the repair. The paper towel was used as low tech breather cloth. The paper towel was held in place with transparent tape.

  • A piece of rope was placed on top of the paper towel. The rope served as a wick.

  • 6 mil polyethylene sheet ("drop cloth" purchased from the paint department at Home Depot) was used as the bag material.

  • Acrylic latex caulk with silicone (cheapest caulk with some silicone I could find at Home Depot) was used as the bag sealant around the perimeter of the bag. Note: Sealant must be placed on the top and bottom of the wing.

  • The bag was folded over the top and sealed.

Applying Vacuum

Brass tube "needle" poked through the bag

and into the core of the rope wick

  • A 1/8" brass tube needle was poked through the bag. The needle is 1/8" brass tubing cut at an angle so that it looks like the needle on a syringe.

  • The "needle" was also poked into the core of the rope wick to evenly distribute the vacuum.

  • Tack tape was placed around the needle to seal the area around the needle penetration into the bag. The rope weather caulking can be used in place of tack tape.

Local Vacuum Bagged Repair

Here's what it looks like while its sucked down.

What's shown in the photo above:

  • The wing with a local vacuum bag sucked down just in the area of the repair.

  • The brown tacky tape sealing the area where the needle penetrates the bag. Latex caulk was used to seal a small leak around the perimeter of the tacky tape. A roll of tacky tape is shown in the upper right of the photo.

  • The syringe used to inject resin under the delaminated skin and spar caps.

  • A small piece of bagging Mylar.

  • The latex caulk used to seal the bag.

Finished Repair

Here's the repair after been removed from the bag.

The caulk can be scraped off (carefully) with a razor blade.

Here it is after the caulk is scraped off.

Photos by Jay Decker, email address:

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