Just something that has been rattling in my head for a few days now. Instead of using traditional foot strap inserts, why not use a block of plastic or carbon and then later after attaching the grip, you could then make the holes and insert a helicoil. Could then also use cheaper screws to secure straps.
Also for something like wing foiling which has even more straps screw holes a common block could be used.

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Henners said..
Just something that has been rattling in my head for a few days now. Instead of using traditional foot strap inserts, why not use a block of plastic or carbon and then later after attaching the grip, you could then make the holes and insert a helicoil. Could then also use cheaper screws to secure straps.
Also for something like wing foiling which has even more straps screw holes a common block could be used.

One word: sand. It's easy to screw current foot straps even if there's a bit of sand in the plastic. A bit of sand in heli coils, and things get ugly.

I see that sand could be a problem but since we are always around water it should not be a real problem (Flikka uses steel inserts). I think it is more about manufactures trying to save costs.

On the other hand, it is way easier to fix a strip plastic insert (you go one size up with a screw) than a helicoil/steel insert because in that case it is more likely you will rip the whole insert from the board (or more broken ankle bones).

I've seen older boards with metal inserts. I wish the current ones had them too.
Easy enough to feel if there is grit in there if you aren't a total Muppet.

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Henners said..
Just something that has been rattling in my head for a few days now. Instead of using traditional foot strap inserts, why not use a block of plastic or carbon and then later after attaching the grip, you could then make the holes and insert a helicoil. Could then also use cheaper screws to secure straps.
Also for something like wing foiling which has even more straps screw holes a common block could be used.

Because even 'stainless' helicoil inserts are not true 316 they will fail they are not intended for longterm use (but do get used that way).
I suspect the big thread self tappers screwed into an engineered plastic have a slight give allowing for longevity rather than a very rigid bolt set up. In reality how often do you unscrew the straps? I set them on new boards ride a few times, maybe reset them and that is that stay in for life!

On carbon yacht racing masts that are damaged eg pulled fixings (I'm doing one right now) you have to do one of a few options, bolt right through the spar into a 316 tapped plate potted/bonded in place with something like spa bond or repair the carbon holes and re tap the carbon elsewhere or lastly inserts, which are much bigger than helicoils and require proper tooling to set well. None of these options are very practical for windsurfing footstraps.

www.stgmachine.com/difference-between-a-key-insert-and-a-helicoil/#:~:text=Unlike%20helicoils%20which%20have%20a,extractor%20to%20remove%20the%20insert.

I've done it as a temporary fix for a stripped plug on a road trip.

Pulled the helicoil and did a proper repair once I got home.

Just to throw another spanner. I think Naish fuselages use helicoils for their front and rear wings. I would think it would be under some level of stress and it would get a fair amount of screwing and unscrewing.

Those flikka inserts look interesting. Looks like two nuts spot welded to a thin plate.
Also looks like a key insert needs a tapped hole but are they both just a piece of shaped wire?

It has always wondered me ... at big hire centres , where they often change strap positions, what happens to their holes ?

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Henners said..
Just to throw another spanner. I think Naish fuselages use helicoils for their front and rear wings. I would think it would be under some level of stress and it would get a fair amount of screwing and unscrewing.

Starboard foils the same, never again. Most have them but ... the build quality a bit lacking

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boardsurfr said..

Henners said..
Just something that has been rattling in my head for a few days now. Instead of using traditional foot strap inserts, why not use a block of plastic or carbon and then later after attaching the grip, you could then make the holes and insert a helicoil. Could then also use cheaper screws to secure straps.
Also for something like wing foiling which has even more straps screw holes a common block could be used.

One word: sand. It's easy to screw current foot straps even if there's a bit of sand in the plastic. A bit of sand in heli coils, and things get ugly.

Agreed. I moved my footstraps on my mistral XLE "screamer" once on the beach and they never moved ever again. It basically had nuts and bolts for footstraps

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Henners said..
Just to throw another spanner. I think Naish fuselages use helicoils for their front and rear wings. I would think it would be under some level of stress and it would get a fair amount of screwing and unscrewing.

Starboard foils have helicoils in their fuselages too, that way the threads remain in good condition when laying on the bottom after the fuse breaks.

Taaroa use helicoils for fuse to wing connections. Easy to replace but unless you're sloppy you won't replace often. Rust isn't an issue but sand can be, especially if you use Tef-gel or anything sss as nd will embed in

My last custom boards I built for myself and good mate I used furniture inserts.
This was in the late 90s and for off set back footstrap on DTL wave boards used on Taranaki coast. Most of the time port tack wave riding but front can come through to NW then starboard tack.

I routered in high density PVC inserts underneath sandwich skin.

They worked really well

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peterowensbabs said..
Because even 'stainless' helicoil inserts are not true 316 they will fail they are not intended for longterm use (but do get used that way).

Depends on your supplier. I'm an engineer that makes stuff that goes into a marine environment, and trust me when I say that you can (and we do!) get Helicoils in AISI 316. Or Bronze. Or Titanium. Or Nitronic 60 if you're worried about your stainless steel bolt seizing up against the insert.

But that's beside the real point: with a soft base material like plastic, if you're going with an insert solution, you'll want an insert that's got significantly more external thread area than internal. Helicoil gets you partway there, but is somewhat limited. In this application, my preferred option would be a solid-body type insert like Keenserts (Howmet) or Triserts (Tappex).

At the end of the day, thread-pullouts seem rare, and could be pretty easily avoided with either one size larger screw from the start, or, ideally, using four screws per footstrap to stop rotation so they don't need to be overtightened so much!

I always thought the reasoning was more to do with the required friction to maintain bite to whatever the required depth is?

if you tighten a threaded bolt into another threaded steel insert, and put a piece of memory foam between the two, the bolt will always roll back a little if it doesn't get tightened/torqued in completely. It'll be almost guaranteed to undo itself unless its torqued up, because steel thread on steel thread doesn't offer enough friction. Steel screw into hard molded plastic on the other hand maintains the required bite/friction as it gets screwed down. It wont undo itself from the depth its been screwed into.

When I've sized inserts with a different industry it was like ozzimark says, the shear strength of the softer material needing thicker threads to take the load.
for springback in softer materials that's the soft stuff expanding back. Joints rely on the whole think compressing a bit and the fastener being less stiff compared to the joint. But a joint significantly more flexible than the fastener will unload immediately. Soft enough and it could take all the preload off the fasteners like you say

For some repair for a guy i use those brass insert i epoxy glue in plastic footstrap insert. He use inox A4 screw with plumbing grease, seem to work.

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I wrote to Flikka asking them about their inserts here is what I got back
Hi Henry,
you have to install them under pvc plates when you make the deck pvc laminate. They actually don't save weight, but they are much stronger.

Best regards/Lep pozdrav

Below is a picture of their inserts, the screws, and just for reference the chinook screws.


Also if anyone is interested the Flikka promo video shows the nuts getting welded and being put into the board

21 seconds to 35 seconds.

So it looks like foot strap inserts get their strength by spreading the load over the board, not embedding it into the board (I understand that the screws do have to go into the board so it needs depth).

The fine thread of the Flikka setup does not seem to be an issue. But I don't know much about these boards except that Bernd Roediger is a team rider.

It's not a very fine thread and it's going into metal anyway so not really a problem. Might have to blow sand out now-and-then.

Won't water get into the board ?

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Imax1 said..
Won't water get into the board ?

Insert seem to be glue in pvc then encapsulated by fiber an resin. For sur nut bottom must be close by something.

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lemat said..

Imax1 said..
Won't water get into the board ?

Insert seem to be glue in pvc then encapsulated by fiber a eahresin. For sur nut bottom must be close by something.

Yeah , I know . I'm talking about the bottom of the screw hole. I'd say the bolt goes through the nut into the foam.

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Imax1 said..

lemat said..

Imax1 said..
Won't water get into the board ?

Insert seem to be glue in pvc then encapsulated by fiber a eahresin. For sur nut bottom must be close by something.

Yeah , I know . I'm talking about the bottom of the screw hole. I'd say the bolt goes through the nut into the foam.

I thought the same thing. But it looks like in the video he has a massive dob of white epoxy on the end.
I was thinking that if possible could use an end nut. Looked on the net and they seem to be called closed-end acorn nuts.
The end nut would just have to have a long enough thread.
The other thing that I thought was a little strange was that the strap inserts are only tacked in two places. If the screw was over-tightened the weld would be the only real place that holds the nut from moving. If the nut is lathered in epoxy then it's the welds and a bit of foam stopping the nut from moving.

So clever. would save a huge amount of build time too.

love the flikka fins. Some of the best fins I've used.

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Henners said..

Imax1 said..

lemat said..

Imax1 said..
Won't water get into the board ?

Insert seem to be glue in pvc then encapsulated by fiber a eahresin. For sur nut bottom must be close by something.

Yeah , I know . I'm talking about the bottom of the screw hole. I'd say the bolt goes through the nut into the foam.

I thought the same thing. But it looks like in the video he has a massive dob of white epoxy on the end.
I was thinking that if possible could use an end nut. Looked on the net and they seem to be called closed-end acorn nuts.
The end nut would just have to have a long enough thread.
The other thing that I thought was a little strange was that the strap inserts are only tacked in two places. If the screw was over-tightened the weld would be the only real place that holds the nut from moving. If the nut is lathered in epoxy then it's the welds and a bit of foam stopping the nut from moving.

The nuts are under the plate , it would be very strong. I love the idea. There could be a cm or so of resin directly under the nuts. You would see the indentations left in the foam. It would be easy to drill a little foam out to do this.In the vid a guy is running a tap through the nut. It could be drilled half a cm past the nut , like in fin barrel nuts. It would be much lighter than divinicelling in plastic blocks. Interesting......