Sandman1221 said..
Got all three inserts out using a 100 mm M6 screw threaded into the inserts, the one in the front was really hard to get out, and I did not want to wiggle it too much while pulling on the screw because of how narrow the fuselage is at that insert, finally just screwed the screw into the insert and when the screw bottomed out inside the fuselage it started pushing insert up, that got it out with no damage to fuselage! The new larger OD M6 inserts will screw into those holes, and will epoxy them in. Not sure if putting more carbon fiber over the inserts will make them stronger, was really surprised how hard they were to get out even though they were loose. The new inserts have deeper cutting threads, and are 3 mm longer, that with epoxy may be enough given the normal forces on the wing force it into the fuselage. Will check with the insert supplier to see what they recommend.

cool please post a picture if the new versus old inserts

FarNorthSurfer said..

Sandman1221 said..
Got all three inserts out using a 100 mm M6 screw threaded into the inserts, the one in the front was really hard to get out, and I did not want to wiggle it too much while pulling on the screw because of how narrow the fuselage is at that insert, finally just screwed the screw into the insert and when the screw bottomed out inside the fuselage it started pushing insert up, that got it out with no damage to fuselage! The new larger OD M6 inserts will screw into those holes, and will epoxy them in. Not sure if putting more carbon fiber over the inserts will make them stronger, was really surprised how hard they were to get out even though they were loose. The new inserts have deeper cutting threads, and are 3 mm longer, that with epoxy may be enough given the normal forces on the wing force it into the fuselage. Will check with the insert supplier to see what they recommend.

Sounds like a good plan. Good that the inserts are slightly oversized and even better if deeper.
I would not worry about the shallow layers of carbon cloth that covered the lip of the inserts originally, it's mostly cosmetic from a strength point of view but would have locked the insert if they were not bonded in.
As you intend to bond the inserts the cloth is not needed and in any case makes life harder as you have to get the wing bedded on to the fuselage seat.
In an aviation repair it may well call for a Cyanoacrylate adhesive to secure the inserts which is normal superglue at least that's the UK name. It's thinner than epoxy and should have a higher bond strength across the two different materials. I would think that epoxy would work fine though and may fill voids better.
The repair should be just as strong as the original but if it does come loose again you can always drill oversize and go a size up or use the Chicago bolts as a repair of last resort. Although I think I would go with mounting inserts from the top rather than Chicago bolts mainly because I think it would be hard to find good quality materials in that type of fastener. Good luck with it, sure it will be fine and will be satisfying to get out on it instead of sending it to landfill.

FarNorthSurfer thanks for the info., really did not want to have to add carbon fiber over inserts. Your point about the carbon fiber being needed to lock the original inserts in because they were not epoxied in makes sense. The new inserts at 9 mm OD require a 8.6 mm hole for hard materials, so existing holes are good at 8.1 mm (may have to drill out a little) but inside there is a slight cavity on one side because the inserts were crooked initially, thinking of adding chopped carbon fiber to epoxy and putting in holes before screwing in inserts. It looks like I may go with a blind insert (solid bottom) and that will prevent any epoxy from getting inside insert and make it easier to screw inserts in and to remove screw after insert is bedded.

Now I could go with a M6 high grip insert that is 12 mm in OD and 14 mm long, versus the blind insert at 9 mm OD and 12 mm long, but then I would have to drill the holes out to 11.6 mm and not sure I want to do that. But the existing holes are deeper than 14 mm, so the extra length is not an issue, and like you mentioned it would be good to have the extra length.

Original inserts are 8.6 mm OD and 9.8 mm long, so rather small compared to the high grip at 12 mm OD and 14 mm long.

FarNorthSurfer said..

Sandman1221 said..

FarNorthSurfer said..

Sandman1221 said..
Got all three inserts out using a 100 mm M6 screw threaded into the inserts, the one in the front was really hard to get out, and I did not want to wiggle it too much while pulling on the screw because of how narrow the fuselage is at that insert, finally just screwed the screw into the insert and when the screw bottomed out inside the fuselage it started pushing insert up, that got it out with no damage to fuselage! The new larger OD M6 inserts will screw into those holes, and will epoxy them in. Not sure if putting more carbon fiber over the inserts will make them stronger, was really surprised how hard they were to get out even though they were loose. The new inserts have deeper cutting threads, and are 3 mm longer, that with epoxy may be enough given the normal forces on the wing force it into the fuselage. Will check with the insert supplier to see what they recommend.

Sounds like a good plan. Good that the inserts are slightly oversized and even better if deeper.
I would not worry about the shallow layers of carbon cloth that covered the lip of the inserts originally, it's mostly cosmetic from a strength point of view but would have locked the insert if they were not bonded in.
As you intend to bond the inserts the cloth is not needed and in any case makes life harder as you have to get the wing bedded on to the fuselage seat.
In an aviation repair it may well call for a Cyanoacrylate adhesive to secure the inserts which is normal superglue at least that's the UK name. It's thinner than epoxy and should have a higher bond strength across the two different materials. I would think that epoxy would work fine though and may fill voids better.
The repair should be just as strong as the original but if it does come loose again you can always drill oversize and go a size up or use the Chicago bolts as a repair of last resort. Although I think I would go with mounting inserts from the top rather than Chicago bolts mainly because I think it would be hard to find good quality materials in that type of fastener. Good luck with it, sure it will be fine and will be satisfying to get out on it instead of sending it to landfill.

FarNorthSurfer thanks for the info., really did not want to have to add carbon fiber over inserts. Your point about the carbon fiber being needed to lock the original inserts in because they were not epoxied in makes sense. The new inserts at 9 mm OD require a 8.6 mm hole for hard materials, so existing holes are good at 8.1 mm (may have to drill out a little) but inside there is a slight cavity on one side because the inserts were crooked initially, thinking of adding chopped carbon fiber to epoxy and putting in holes before screwing in inserts. It looks like I may go with a blind insert (solid bottom) and that will prevent any epoxy from getting inside insert and make it easier to screw inserts in and to remove screw after insert is bedded. Now I could go with a M6 insert that is 12 mm in OD, versus 9 mm OD, but then I would have to drill the holes out to 11.6 mm and not sure I want to do that.

If there is hole damage then as you say have a go a restoring the sides as that will support the loads on the insert. The 9mm inserts would be the way to go, you can always go bigger if it fails.
Take care with the blind inserts as they will hydraulic lock when screwed in. Should be OK if you go slow.
No reason why a slightly larger insert with it's bigger surface area will not be stronger than the originals.The W95 fuselage has plenty of material around the hole to support the enlarged hole size.

Okay, thanks FarNorthSurfer, so what do you think about the M6 12 mm OD x 14 mm long insert? You are right, there is enough material there, really do not want to have to deal with this again. The 12 mm insert is open ended. Maybe a one and done solution. The 9 mm OD insert is not going to cut new threads on the side where the hole got enlarged below the surface due to the inserts getting cocked.

Not suggesting you do this at this stage but it's worth bearing in mind that if all else fails you could always drill right through the fuselage and simply Nut and bolt the wings on using SS nyloc nuts and washers!
I know what your thinking, that will look crap, and won't it slow me down, loads of drag etc.
Well that's exactly what I did with a Slingshot fuselage and wing when I didn't have a new mast cap. Just drilled straight through and Nut and bolted it.
Looked a bit crap but worked fine and I could detect no difference in performance, although that could be me :)
Better than spending another grand on a W95 mast.

Hey FarNorthWindsurfer, here are pic of the different M6 inserts, any comments appreciated. Thread depths look about the same but getting spec. for the heavy duty tomorrow. The vertical grooves in the heavy duty inserts help with cutting grooves and also allow epoxy to fill that area for a super strong bond.

12 mm OD x 16 mm blind heavy duty

12 mm OD x 14 mm through tapped heavy duty
9 mm OD x 12 mm blind

FarNorthSurfer said..
I would go with the 9mm for the reasons I gave earlier. They look fine. The threads are for wood applications so I wouldn't expect to get full thread depth in a carbon composite.
The potting epoxy will do that job. The vertical grooves will lock the insert and prevent it from turning under torque load. Go for it :)

Do mean the 12 mm OD insert vertical grooves will make it really hard to screw into the hole because it is carbon fiber, versus wood?

FarNorthSurfer said..

Sandman1221 said..

FarNorthSurfer said..
I would go with the 9mm for the reasons I gave earlier. They look fine. The threads are for wood applications so I wouldn't expect to get full thread depth in a carbon composite.
The potting epoxy will do that job. The vertical grooves will lock the insert and prevent it from turning under torque load. Go for it :)

Do mean the 12 mm OD insert vertical grooves will make it really hard to screw into the hole because it is carbon fiber, versus wood?

No, I just meant all the inserts are made for wood not composite so you won't get full cut thread depth.
But that's fine. Use the 9mm OD in my view these will be good in the holes you have when you bond them in.

FarNorthSurfer, So I am concerned about using the self tapping inserts on carbon fiber, like you said they are really made for wood and the threads will not cut all the way in on carbon. The other option is to use an M6 insert with an M10 outer thread, then I can tap the holes for M10 and just glue/screw in the insert. Less damage to the carbon, and since the holes are close to 9 mm can probably just tap them the way they are. What do you think? those inserts are also A4. A tap will self center making it a lot easier than trying to use a self tapping insert with coarse threads in carbon.

I don't think you would have much success trying to tap the fuselage to 10mm without special tooling.
You said earlier the holes were about 8.1mm maybe larger but less than 9mm.
The 9mm inserts will grip the sides and have some support in the holes but the primary locking will come from the epoxy adhesive around the insert.
The adhesive will spread into the voids in both the hole and the threads of the insert. This provides a mechanical lock in the hole as it will be a blob of epoxy set in an irregular cavity. Indeed this is how aviation inserts work in composite structures.
Remember the original inserts were not bonded in and were very strong.
You could if you prefer try bonding the original inserts in to the holes. But would need to make sure the alignment is good as they will move more in the holes.
As before starting with 9mm insert allows you to go bigger if this doesn't work.
Give it a go, sure it will be much stronger than you think. :)

Sandman,

Before reinstalling the hardware you may want to go to the link below and read the Gougeon Brothers article about bonding fasteners.
Even though they are talking about wood the same techniques would apply to your repair in carbon. When using the right epoxies and filler the mechanical bond should be adequate. If you read further on their website they back up these techniques with real testing.

www.westsystem.com/instruction-2/epoxy-basics/bonding-fasteners-hardware/

Points to note and a possible setup to hold the inserts:
1. Over drilling the hole size is not an issue. In fact it provides more surface area for the mechanical bond'
2. After the holes are drilled, first partially fill them with resin and thoroughly wet out all exposed fibers.
3.) Mix up a small batch of resin with the appropriate structural filler. Fill the holes.
4.) Lightly press in the inserts until they are located at the correct position. Wipe up the excessive resin.

You may be able to drill a strip of wood with 3 tight clearance holes for M6 screws at the correct spacing. A nut on each side of the wood would allow you to adjust the screws vertically if they are at different heights due to the wing curve. The inserts can then be threaded onto the end of the screws and the height fine tuned. Wax on the screw ends would make them easier to remove. You will need to figure out how to hold the assembly along with the fuselage during the gluing operations. You can do a practice run dry to make sure everything will remain stationary.

Julien from AFS finally got back to me, they were down two people. Like many above, he recommended drilling holes though the fuselage and then inserting the inserts from the opposite side (top), that is how they do it with their new foil. I checked the depth of the existing holes, and 2 out of the 3 are 80-90% through the fuselage, the one in the rear maybe 60-70%. But I would rather not have to drill though, even though it would be the strongest attachment. But it takes more precise work than just putting in new inserts with oversized cutting threads that will engage in the existing holes.

Followed the Riowind link at westsystems.com to this site, talked about epoxying in studs for windmill blades, really gives me confidence that epoxied in inserts should hold up great if done right.

www.epoxyworks.com/index.php/hardware-bonding/

Sandman1221 said..

Riowind said..
Sandman,

Before reinstalling the hardware you may want to go to the link below and read the Gougeon Brothers article about bonding fasteners.
Even though they are talking about wood the same techniques would apply to your repair in carbon. When using the right epoxies and filler the mechanical bond should be adequate. If you read further on their website they back up these techniques with real testing.

www.westsystem.com/instruction-2/epoxy-basics/bonding-fasteners-hardware/

Points to note and a possible setup to hold the inserts:
1. Over drilling the hole size is not an issue. In fact it provides more surface area for the mechanical bond'
2. After the holes are drilled, first partially fill them with resin and thoroughly wet out all exposed fibers.
3.) Mix up a small batch of resin with the appropriate structural filler. Fill the holes.
4.) Lightly press in the inserts until they are located at the correct position. Wipe up the excessive resin.

You may be able to drill a strip of wood with 3 tight clearance holes for M6 screws at the correct spacing. A nut on each side of the wood would allow you to adjust the screws vertically if they are at different heights due to the wing curve. The inserts can then be threaded onto the end of the screws and the height fine tuned. Wax on the screw ends would make them easier to remove. You will need to figure out how to hold the assembly along with the fuselage during the gluing operations. You can do a practice run dry to make sure everything will remain stationary.

Riowind, thanks for the detailed information, I was planing on using self-tapping inserts, so as long as I start turning them in straight, they should self center since the holes have good walls (checked with an ear scope) then I will not need an alignment jig. Here is pic. of fuse. in a vice using pipe clamp. Could also use a drill press to align the inserts over the holes, and when good hand turn the chuck to tap in the insert into the epoxy filled hole.

Honestly I believe AFS do this by hand at the factory.
You would think they have jigs or fancy machines but from the variability of the wings and fuselages I have had and seen the tolerances are just not that close.
That said the foils perform really well so who cares if they are hand built.

Riowind said..
Sandman,

As I said in your other thread you can probably use the wing as your drill template. Carefully align the wing on top of the fuselage and clamp it with one or two small C-clamps. Find a drill bit that is about the same diameter as holes in the wing and carefully drill through the fuselage. You can enlarge the hole slightly if required. I think the outside diameter of the M6 Chicago bolts are about 7.5mm if you decide to go that way. McMaster has about every size drill bit that you could possibly need.

Riowind, the thing is, the current ~8.6 mm holes go pretty far through, so if I drilled in from the other side I would make a 8.5 mm hole all the way through! Now Julien diagramed how to fill in the original hole with thickened epoxy, but just seems risky. I do not want to remove any carbon, if possible.

Sandman,

As others have mentioned you may want to consider using Chicago bolts (Binding Barrels) instead of the threaded inserts. They should be stronger and I think they also can be aligned better during installation. It was also previously mentioned that several other manufacturers use them including AFS.

You don't have to drill an 8.5 mm hole through the remainder of the fuselage. It only has to be large enough for the 7.5 mm diameter barrel to pass through. As I mentioned above you can probably use the wing as your drill template. Carefully align the wing on top of the fuselage and clamp it with one or two small C-clamps. Find a drill bit that is about the same diameter as holes in the wing and carefully drill through the fuselage. You mentioned that the hole are already 90% through the fuselage so there isn't very much material to remove. The clearance hole in the wing may be slightly less than the Binding Barrel diameter. If so just use a slightly larger drill bit after removing the wing to increase the hole size. Ideally you should be able to insert the insert with a light bit of pressure. McMaster has about every size drill bit that you could possibly need.

Since the Binding Barrels will carry a partial load without the epoxy you should be able to install the wing to check the barrel alignment before applying the epoxy. If necessary you can slightly increase the hole sizes for better alignment.

One poster on your other thread gave some good advise. "Rough the inserts really well with a dremel or similar, soak in acetone for an hour, blow off and repeat. That's the only way to really ensure no oils.."

Install the Binding barrels using the Six10 epoxy. You can also put a bit under the heads if the surface is slightly rounded or if any of the surface fibers were damaged during drilling. Clean up any excess adhesive from around the barrel head and tape over the head to hold it against the fuselage. Also wipe up any excessive resin from the surface where the wing mates. You may want to screw a waxed fastener into the barrels to prevent the epoxy from getting on the threads. As alternative you could also place a layer of thin Mylar packing tape over the fuselage surface where the wing make contact and cut out the holes with a razor blade for the screws to pass through. Installing an over sized washer with a short waxed M6 waxed screw would also keep the barrel in place.

To further ensure the alignment you could also install the wing before epoxy has cured. Lay one strip of thin Mylar packing tape on the wing where the fuselage makes contact and cut out the screw holes. With the barrel heads taped firmly to the fuselage, attach the wing using waxed screws and lightly tighten them. Leave them installed until the epoxy has cured.

Ideally you want the barrels to be the length as the fuselage depth. McMaster sells Binding Barrels in 316 stainless with an M6 thread in a variety of lengths so you can come close to matching your fuselage thickness. If they are a bit too long you can add a 6mm washer under the Binding Barrel head. Typical stainless steel washer are about 1.5mm thick. You can also grind or file off a bit off the length. Shorten them before installation to avoid generating excessive heat that could damage the epoxy bond. Check the threads after grinding and clean them with a tap if necessary.

Super-Corrosion-Resistant 316 Stainless Steel Binding Barrels

Sandman,

The only thing I would add to the binding barrel procedure is that you can plug the threaded holes with a waxed set screw instead of a regular head because the head will not fit through the hole when installing the insert. A bit of clay can also be used.

Regarding the threaded insert installation. If you encounter a lot of pressure when threading them in drill the holes a bit larger. Too much pressure will result in dry joint between the screw threads and the sides of the holes. You want to have the epoxy create a mechanical bond between the screw and the carbon. As one other posters commented above carbon does not tap very well because it it brittle and tends to break. You don't want fractured fibers and a dry glue joint. With your approach you want just enough material allow the insert to engage and thread in straight. The epoxy will fill the gaps and create the bond. This is different than an installation in wood where you drill a pilot hole and are cutting threads into the wood. Over drilling the hole size and pressing in the inserts into the epoxy would still be the preferred method if you have a way to keep them centered and straight.

When installing the inserts first thread a nut onto the M6 screw that you are using to turn the inserts into the wing. After threading the screw almost to the bottom of the insert lock the nut against the insert, That will prevent the screw from tightening against the bottom of the insert and possibly jamming. You can then hold the screw and loosen the nut prior to removing it from the insert.