Covering ultralight wing with undercamber

[BBerson]

That's the trailing edge, not the rear spar. It is a single spar wing.
I don't see any aileron hinges. So not sure if it has ailerons on that wing.

 

[mrd]

Would point out that just 'large head pop rivets' is not really suitable as the heads will chew through the fabric, the large plastic washers are a slightly better idea, but fiddly and expensive when you start buying two or three hundred of them!
My usual (before I found the Foxbat method) way is to lay the fabric glued around the edges, give a light shrink till flat, dope a pre-ironed, one inch wide pinked strip along the rib, then run a length of half inch wide fibreglass reinforced packing tape along the rib.
Using a scriber, locate the riveting holes and prise the fibres of the tap and the fabric aside and insert large head rivet.
Finish with a two inch pinked fabric strip and final shrink before dope layers.
I've never tried stitching...

Hi Where did you get the glue/silicone for your Foxbat test -000repair?Thanks

 

[pylon500]

Hi Where did you get the glue/silicone for your Foxbat test -000repair?Thanks

This started off being a confusing chase as the number quoted in the Foxbat manual didn't show up in the 3M catalogue.
So after reading all the 'similar' tech pdf's, I ended up looking through the Sika range of adhesives and settled on the SikaFlex252 polyurethane marine adhesive, which was fortunately stocked at my local hardware store.
Sika252
I've used both black and white, just depended what they had in stock at the time (it does have a shelf life), but it does cure a bit quick so I did the gluing in sections and tended to skip the 'roll the adhesive up through the fabric to a plastic backing' technique and just rolled and squeegeed(?) the glue through the fabric with small plastic trowels and aluminium roller.
Extremely messy, but ended up with a better finish than when I did the roller and plastic strip version (which ended up with lumps).


Found that doing four or five ribs at a time gave enough time to properly work through and clean before it started getting over tacky.
Have had no problems with the two aircraft I repaired, one over eleven years ago.

 

[mrd]

Thank you for this information. In the Foxbat method they use some cleaners etc. to prepare the metal. What did you use? I have a Foxbat that needs wings etc recovered. Thanks again for your help

 

[Built2Fly]

That's the trailing edge, not the rear spar. It is a single spar wing.

Thanks. I will call it the "trailing edge". What I am trying to say is that the trailing edge indeed fixed the distances between individual ribs. So if you take that into consideration, there are three ways to stress and distort the wing as one piece: (1) up and down, (2) fore and after, and (3) rotation / torsion.

(1) Up and down. This is controlled by the flying wires. Even though there are two flying wires for the Hiperlite, they are very close to each other (1 inch apart). So it is just for up and down direction only and did not resist much of the torsion.

(2) Fore and after. This is controlled by the drag tube inside the wing. The tube is pretty thick in size and should take good care of that. It is why there is no gussets at the cap strips to the spar and the trailing edge, and only one rivet holds the cap strip to each end. The gussets are not needed.

(3) Rotation / torsion. As mentioned, the flying wire did not provide much torsion resistance at all. So the ribs themselves and the four rivets holding them to the spar got to do it. I think it is in this direction that the cap strips on ribs provided some structural support. Your theory that the cap strips strengthening the channel into an I-beam makes sense.

Therefore, at this time I conclude that the cap strips are structural for this design. And my course forward will be to leave the cap strips on and glue the fabric onto those strips. (I have yet decided if I would drill a couple of 1/8" holes on each ribs in case I would need them sometime in the future.)

 

[pylon500]

Thank you for this information. In the Foxbat method they use some cleaners etc. to prepare the metal. What did you use? I have a Foxbat that needs wings etc recovered. Thanks again for your help

In the FoxBat/3M covering pdf's, 3M and Teroson cleaners and primers are mentioned. When I used the Sika range of materials, I read their pdf's which suggested that Sika TDS210T primer was best (and fairly expensive) but was not available where I was getting the adhesive without waiting another month on order, so I ended up using Sika TDS 206GP primer, which was also more affordable and readily available.
I would point out that the test piece I made was just cleaned with acetone prior to just applying the 252 adhesive directly, and is still as strong today as it was eleven years ago.
I'm not sure how much more effective the cleaners/primers/activators make the bond as the polyurethane adhesive seems to 'stick like the proverbial' and it's more a case of clean preparation of the surface before application.
I find acetone is best for 'degreasing/cleaning/drying' a surface, and is only problematic if the humidity is fairly high in which case it's quick evaporation can cause noticeable cooling and attract moisture to the surface. If it's fairly humid I will change to using Methylated Spirits (I've no idea what Americans call this stuff), which has a tiny bit slower vaporisation point. It's also usually a lot cheaper, so I tend to use it everywhere.

 

[Protech Racing]

This started off being a confusing chase as the number quoted in the Foxbat manual didn't show up in the 3M catalogue.
So after reading all the 'similar' tech pdf's, I ended up looking through the Sika range of adhesives and settled on the SikaFlex252 polyurethane marine adhesive, which was fortunately stocked at my local hardware store.
View attachment 106779 Sika252
I've used both black and white, just depended what they had in stock at the time (it does have a shelf life), but it does cure a bit quick so I did the gluing in sections and tended to skip the 'roll the adhesive up through the fabric to a plastic backing' technique and just rolled and squeegeed(?) the glue through the fabric with small plastic trowels and aluminium roller.
Extremely messy, but ended up with a better finish than when I did the roller and plastic strip version (which ended up with lumps).
View attachment 106781
View attachment 106782
Found that doing four or five ribs at a time gave enough time to properly work through and clean before it started getting over tacky.
Have had no problems with the two aircraft I repaired, one over eleven years ago.

How does the 252 compare with the 3M 5200?
Thanks,MM

 

[mrd]

In the FoxBat/3M covering pdf's, 3M and Teroson cleaners and primers are mentioned. When I used the Sika range of materials, I read their pdf's which suggested that Sika TDS210T primer was best (and fairly expensive) but was not available where I was getting the adhesive without waiting another month on order, so I ended up using Sika TDS 206GP primer, which was also more affordable and readily available.
I would point out that the test piece I made was just cleaned with acetone prior to just applying the 252 adhesive directly, and is still as strong today as it was eleven years ago.
I'm not sure how much more effective the cleaners/primers/activators make the bond as the polyurethane adhesive seems to 'stick like the proverbial' and it's more a case of clean preparation of the surface before application.
I find acetone is best for 'degreasing/cleaning/drying' a surface, and is only problematic if the humidity is fairly high in which case it's quick evaporation can cause noticeable cooling and attract moisture to the surface. If it's fairly humid I will change to using Methylated Spirits (I've no idea what Americans call this stuff), which has a tiny bit slower vaporisation point. It's also usually a lot cheaper, so I tend to use it everywhere.

Hi Thanks again I am in Perth .Yanks call it de “something “alcohol.

 

[mrd]

Further, what covering material and weight did you use? Thank again

 

[pylon500]

Further, what covering material and weight did you use? Thank again

FoxBat manual calls for Diatex 1500 EV3, which according to the Diatex website is 89g/m², which make it about the equivalent of Ceconite 102.
I would have liked to have used Ceconite un-cert light, but I don't think you can get it now, and I have to stick to the specs for a certified aircraft, sort-of.
Apart from using the Sika glue down system, the rest of the recover was as per the Ceconite system using nitrate and then aluminium-butyrate dopes before painting with a two pack with a flex-aid added.