Having an inducer pop off on first rotate is really annoying and can lead to you avoiding using a sail. Some are really hard to get on but to have them come off after all that effort is infuriating. "Experts" will tell you not enough downhaul not enough outhaul, wrong mast etc but some sails are just built badly . My Foilglide 8.0 popped the camber just below the boom every time until I tied it in as per photos. I can now rig it to the numbers and it just stays on.
Remember to undo the reef knot before you release the downhaul. 3 mm rope. Doesn't have to be particulary tight.

Did it pop off from new or get worse. From the picture it looks like an old cam with corrosion on the roller pin.

what did Severne say?

Someone gonna say it, more downhaul. I had a turbo gt that did this when I tried letting some down haul off on a light wind day

Good one improvit. Thanks for sharing your idea. If you're happy with the response of the sail, and it's popping this cam, then this is a good solution. The only other thing I could suggest is a different brand of camber. The KA cambers have wings/guides? on the ends to stop this from happening.

When the cams are hard to get on, are you remembering to tension the outhaul and then back off the downhaul before slipping on the cams ?

Do the Foil Glides have shims like the HGOs do? The cam appears to be the shape that would take a shim (or two). fwiw, batten tension on the HGOs has a notable effect on cams popping over, and I'd think it would help with their retention.

Tieing and untiring the rope must be a pain. The numbers are only guides. As you said there are variances in manufacturer. Rig to suit the sail / mast you have not the ideal as indicated by the rigging numbers. Have you tried increasing downhaul and or inserting shims till the cam stays on?

What mast is it rigged on?
A top-flex mast will not bend enough at the boom-cutout height.

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SurferKris said..
What mast is it rigged on?
A top-flex mast will not bend enough at the boom-cutout height.

Spirals suggest Severne.

I also think shims, the batten could be 1mm too short or anything
downhaul to numbers.. With a Severne extension? In an old Chinook you will be 4cm short if u use the numbers.
It is a novel solution but there's a lot of things to do first.

and there are a lot of very experienced people here who would know straight away with a pic of it rigged

Shims was my thought also.
With sail rigged to spec, see if you can "pinch" the luff sleeve adjacent to the troublesome cam. That will show any slack. add shaims until there's still a bit of slack, but you can't pinch a fold. If it's too tight, it will be hard to rig and rotate, but you don't want any slack.
The sail won't set to it's intended shape, and guess what, cams can fall off.

Severne blue rdm as specified. Have shims in , know how to put cambers on and rollers spin fine. As I said lots of experts about as above demonstrates but after 40 years I have got the idea. Suppose I am a bit biased against downhauling the death out of sails for light gusty wind especially a foil type but I do it to their numbers and it flops about as required
Tried the various things but there is nothing more infuriating to have all the right water conditions, try it on the beach, get on the water, gybe and pop. My 7.0 works fine...less cambers of course. I suspect there was a reason the guy sold it to me as used twice..
Takes all of 20 seconds to tie and untie a reef knot. Works a treat, pump away and off. You dont have to remember any special tricks for rigging that specific sail you only use occasionally.

Just a last comment for context. All good suggestions above but I offer this solution to the less patient who dont want to waste their limited sailing time re-rigging.
People who go foil surfing in 10 knots specifically will identify with the awkwardness of getting a big litre board with large foil and big sail to the water without damage. To have to return and take the rig apart to fix the inducer but not trusting it to stay there is something to avoid. You need it on though as its your power. A quick drill and 150 mm of rope and its done...why not?

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improvit said..
As I said lots of experts about as above demonstrates but after 40 years I have got the idea.

If you had said you had added shims and it didnt work, then "experts" wouldnt suggest adding shims. If you had said it had happened from new, then people might not suggest it might be because the cam is worn out. The "experts" are only trying to help.

I just did a google search of "Severne RDM SDM cam" and the images returned had RDM made from red plastic, SDM in black. I dont use Severne, is that actually the case, or google playing tricks on me?

Yesss it's an SDM cam

could probably improvit with an RDM cam
thats even better for the less patient sailor

good pickup Phil. 40 years, but 40sec for Phil to google

Experts, who needs them.

Yes. I've learnt the hard way not paying enough attention and having a sail with cams for sdm on an rdm and vice versa.
My Severnes are 2017 - 2021 so I'm not sure if they have changed the specs.
My rdms cams are 4mm longer than the sdms so if you replace that cam with an rdm ( red one) that could solve the problem??

As an alternative to your rope method, try using flat velco strap - the way old external CAM's use to be fitted

Or the correct cam ..

The SDM cams pop off the RDM mast due to not enough cam pressure, as a few people pointed out. The RDM cams are longer then SDM to make up the larger gap between the batten pocket and mast. Just tying the SDM cam to the mast will mean a gap between batten pocket and cam, and possibly the rollers not being in the correct place.

I have a 2019 Severne Overdrive M2, which rotated really nicely on RDM with RDM cams. I recently replaced it with the 2023 M4 version. The new sail was set up for SDM so I replaced the cams with the black ones. The batten under the boom just wouldn't rotate. On closer inspection the previous owner had put in a 1.5mm shim. Removed that, and it now rotates and feels identical to the older sail.

Well there we go....doh...wrong cam. Previous owner must have been using sdm despite rdm spec. Explains why 3 shims in.
My 7 has red so I will give it a go although it only takes a minute to tie the knot and guarantees success. With rdms being a bit longer I'll get push shove and swear to get it on too or back off the screw/shims....hmm...it was just nice amount of effort as is but we have an explanation.

Velcro suggestion...have to glue or fiddle about a bit more than rope.

Thanks for all the thoughts...appreciated .My $1 bit of string is a really easy answer .It might help other casual sailors that would like to reduce batten length so they get a cam to be a bit more user friendly.
It is about easy... not dreading breaking a batten , jamming your finger in a sleeve or thinking something will explode if anymore downhaul goes on.

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improvit said..
Well there we go....doh...wrong cam. Previous owner must have been using sdm despite rdm spec. Explains why 3 shims in.
My 7 has red so I will give it a go although it only takes a minute to tie the knot and guarantees success. With rdms being a bit longer I'll get push shove and swear to get it on too or back off the screw/shims....hmm...it was just nice amount of effort as is but we have an explanation.

Velcro suggestion...have to glue or fiddle about a bit more than rope.

Thanks for all the thoughts...appreciated .My $1 bit of string is a really easy answer .It might help other casual sailors that would like to reduce batten length so they get a cam to be a bit more user friendly.
It is about easy... not dreading breaking a batten , jamming your finger in a sleeve or thinking something will explode if anymore downhaul goes on.

I suggest you try it with matched cams and mast. I had the foil glide 7.0 with rdm mast and cams. It was easy to rig. The sail was stable and rotated easily. I had no issues with cams coming off.

Cams are used to induce camber in the sail. They wont be effective if they dont touch the batten pocket because the cam is too short. Whats the point of buying a cammed sail if its not effective?
Didnt the previous owner give you the RDM cams that came with the sail originally, or did he buy the sail secondhand with the SDM cams?

Improvit could maybe add sorry Severne

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improvit said..
Well there we go....doh...wrong cam. Previous owner must have been using sdm despite rdm spec. Explains why 3 shims in.
My 7 has red so I will give it a go although it only takes a minute to tie the knot and guarantees success. With rdms being a bit longer I'll get push shove and swear to get it on too or back off the screw/shims....hmm...it was just nice amount of effort as is but we have an explanation.

Velcro suggestion...have to glue or fiddle about a bit more than rope.

Thanks for all the thoughts...appreciated .My $1 bit of string is a really easy answer .It might help other casual sailors that would like to reduce batten length so they get a cam to be a bit more user friendly.
It is about easy... not dreading breaking a batten , jamming your finger in a sleeve or thinking something will explode if anymore downhaul goes on.

End of the day, as long as you're happy with the performance of the sail. But in my hands, rigged like that, it would probably handle like a slow POS that can't get up wind and everybody sailing past me.

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improvit said..
Well there we go....doh...wrong cam. Previous owner must have been using sdm despite rdm spec. Explains why 3 shims in.
My 7 has red so I will give it a go although it only takes a minute to tie the knot and guarantees success. With rdms being a bit longer I'll get push shove and swear to get it on too or back off the screw/shims....hmm...it was just nice amount of effort as is but we have an explanation.

Velcro suggestion...have to glue or fiddle about a bit more than rope.

Thanks for all the thoughts...appreciated .My $1 bit of string is a really easy answer .It might help other casual sailors that would like to reduce batten length so they get a cam to be a bit more user friendly.
It is about easy... not dreading breaking a batten , jamming your finger in a sleeve or thinking something will explode if anymore downhaul goes on.

I'm thinking the sail shape will be all wrong with the incorrect cams.

Just to finish this off....my glide 7.0 rigs perfectly and rotates nicely as John340 says.
I rigged it the other day using a rdm cam on troublesome one. Yes I got it to work just with downhaul to spec.
Real issue was it required a huge pull to rotate. Its hard enough balancing in a gybe without a huge yank to get it rotated. Might be ok on the water but not in the air. So I will stick with my answer .
Photo fyi of cams.

NOW you have the correct cam, you tune with settings and maybe shims.

Sometimes they are hard to rotate until you do. With any sail of any brand.

You seem intent on keeping this 'bagging out Severne' thread going. After your big whine about their extension a couple years ago, and very little else posted, I smell a rat.

That last photo highlights why the shorter SDM cam will do nothing to induce some camber into the batten, which is why its there. I'm wondering if it actually touches the batten pocket.