Hi

My wife Windfoils a Sabfoil (W799/W399) on an older fixed Tracks 93K Mast, 899HS Fuselage. Does a lot of foiling on this setup, 30-4km a session and about 130-odd sessions last year alone. However I have been seeing issues with one Mast/Fuse screw (leading edge) loosening after EVERY session, normally 2-3 hours, continuous use.

It's used on a freefoil (JP Freefoil 105/115 or 130 as conditions dictate), but at 59kg she does not "load" up the foil too much (at all), especially as she is not racing, just freefoiling (swell riding mostly). I tried spring washers, and as I disassemble that connection every time I am loathe to use Blue LocTite or slr. Plumbers tape was an idea but seems messy. I have been using a washer (as it seemed the right thing to do) which means the screw is not quite in as far as it could be, by the washer thickness. I will try without the washer, which might work if tejh screw thread mates with the few "realtively new" threads at the bottom of the threaded socket.

When I put the connection together using just the screws (no washers) it appears snug, not movement, despite what I am about to say next.

However when I just put the mast into the slot, it feels like it 'rocks' in the the middle, never quite "seating" as I expect good Italian Engineering to... (sorry that was a sneaky poke at my Dad's Fiat 124, which was fabulous car, went like stink but rusted like crazy and the toothed timing belt always went out of whack; great design, terrible implementation... but I digress).

The video links below show what I mean (I rock it until I can feel either the leading or trailing edge stops), but at no point does it feel like it is seated. When I do up the screws it does seem snug, like you'd expect jamming a cone into a slot, but it does not feel right.

I have taken a few self-explanatory photos (with a straight edge, into the light, where you can see some minor gaps, esp at the ends) and some initial measurements, with an eye to seeing if it is proud in one point (top) or bulging at the sides, if the screws are too long (they seem OK) etc (although I wasn't able to get a measurement of the thickness of the fuse from the bottom of the hole to the slot, I am hoping it is more than ~12.5mm (I can probably measure the total fuse depth at the hole location, and then use the little alu bar that comes out of the end of the calipers to deduct (a) hole depth and (b) slot depth... that comes next, but does not explain the rocking).

There is a bit of a wear mark on the top edge, middle third. Excuse the micrometer attempt, not scientific but I tried to seat it on the lip between the angled part and the mast-proper. I put the stright edge into the slot and the alu fuse seems flush and flat; no rocking there.

Before I go do something stupid I cannot undo, like file or sand something down, I was hoping to get some feedback from collective wisdom and experience here, as well as owners of this particular model.

Cheers,

k.

Videos of the rocking:

imgur.com/0K39atY
imgur.com/eTE7DUz

thedoor said..
Presumably she is taping the fuse on with a rubber mallet before tightening fully?

Ah, no . probably not. I bought it second hand so wasn't aware of that requirement in the assembly instructions. Seems question was discussed in 2021. Same issue.

I will give it a go; hopefully I won't become the victim of said mallet should I comment on the fitting of her wetsuit.

cad184 said..
Normally the screws should not get loose after this. It is also better for the threads of the screws if You do it like this and not pull the mast into the fuselage only with full power on the screws.

Thanks, I will give the wiggle, two phase install, mallett-tap prep routine a go. Hopefully haven't stuffed it up already, as I will admit I (she, under my direction) have been tightening it just using the screws, which are only M6.

I use a T-shaped handle screw with an M6 Socket Adapter, and I chose a pretty small "T" so that no-one could apply too much torque. I'm not bringing a torque wrench to the beach, it will just corrode PDQ.

Two stage assembly seems to be the way to go, I usually leave a little bit of time in between the two stages as well.

WsurfAustin said..
I would "think" a high spot between the bolt holes would contribute to rocking "BUT", that doesn't appear to be the case in your photos (great job BTW showing the issue). If anything the material tapers off at each end, which does reduce planar contact between the fuse and mast. That only leaves a very small amount of surface area around the bolts to make contact between the fuse and the mast creating a very high load on a small surface contact. I can see where the bolts would get looser. If it were mine, I would add material at both ends to get more surface contact to reduce the loading at the fastener interface. Now, how to do that would be the tricky part. Any shim type material that was compressible wouldn't do much good. Possibly adding composite/epoxy to build up that area on the mast, then sanding back to a hard planar surface . Maybe Azymuth could chime in as he does a lot of modifications with composites etc.

Yeah,

See @thedoor's pics here www.seabreeze.com.au/forums/Windsurfing/Foiling/Replace-SABfoil-M92-Fixed-Twin-Track-Mast-Inserts-connecting-to-Fuse-?page=1 two of which I have reproduced below (credit to @thedoor), which shows the U-shaped 'yoke' embedded in the top of the mast that forms the connection for this particular model. That thread was actually about a daft idea I had to replace the inserts wih barrel nuts (like Sabfoil seem to have done on the upgraded Kraken version, go figure...).

Anyway over time I am guessing the threaded parts at each end pull upwards a wee bit forming the raised hard spots you see in my photos. I was originally thinking to gently sand back the top of the mast at these spots over the holes, but I am not convinced this will help, they will probably just pull up the theraded part even further.

azymuth said..

WsurfAustin said.Maybe Azymuth could chime in as he does a lot of modifications with composites etc.

I would use the fuse as a mould (spray with mould release).
Paint epoxy on the mast base (sand and clean first) and screw it up with the foil mast pointing up, so gravity pools the epoxy in the little voids at the bottom of the masthead/fuse and the sides.
To be safe coat the screw threads with soap.
Use enough epoxy so it spills out a little all round.
In my experience the epoxy will stick to the mast and fill the gaps.
You might have to whack it with a mallet to separate it - it's worked the 3 or 4 times I've done it.
It's pretty simple

Mine has good fit but I still have to apply pressure on the front wing on the beach to tighten the front screw (as others have described) - but it stays tight for the session.

Hmm, interesting approach. Maybe if the mallett-wobble sequence doesn't work I will have a crack at doing that.

I am guessing you'd need to make sure you did do the mallett-wobble sequence straight after you painted on the epoxy, so you got the tightest fit. I'd be a bit worried this would squirt epoxy out somewhere unwanted but it's certainly doable.