any downsides to shimming stabiliser and big wing mast length

[neilhapgood]

hi all,

are there any down sides to shimming a foil? It seems counter intuitive to have the wings working against each other but I presume its such a subtle thing you don't notice, and also done with big wings so not looking to go fast?

I am looking to get a bigger wing working on a moses T40 which apparently requires a shim so wondering if anyone has shimmed and not liked it and ended up getting a board with a track instead?

Also most big wing packages come with a shorter mast, is this important or will a 90cm mast be ok?

a very boring post after just reading the rubber duck one I am afraid!

[Mossy 757]

Shims are great, and the best part is that if you don't like it, you can usually go back the way it was by loosening one or two screws. I've shimmed both foils I've owned at this point and felt like it helped. I'm about to get a brand new foil that has a fixed tail, but even that can be shimmed at the fuselage-to-strut junction.

Try it, report back. I use the thin plastic that milk jugs are made from, or an old hotel room key if I need more width.

[Flag53]

I have the Moses T40 and have used the Onda 633 on it on a variety of mast Lenghs 70/90/101

I’ve found that shimming the Mast to fueselage works best as there’s no cavitation and as Mossy says
It’s easy to do and if you don’t like it it’s easy to undo .

[Peter_Frank]

Yes, there are downsides when shimming...

No downsides of longer mast combined with the big wings.
But IMO loads of downsides of a shorter mast, but we can never agree on this one, I know.
It is a reminiscence from SUP that does not make sense in waves with a kite I would say, but some like the short ones for whatever reason.


When you shim the stabilizer, I have found the complete setup to feel bad when carving - you can shim the trim to be spot on to where you stand, but when you carve the dynamics seems to suffer if you shim the rear too much, both ways are wrong in fact, but at least if you shim to be able to stand further rear (like with the Moses, and another board I had) meaning rear stab not pulling down much or at all, the turning becomes stiff and odd.

In my experience - I dont know what others think?

Mast to fuselage shim will not alter turning abilities in this very respect at least, so a safer option if I am right you will alter the turning often to a worse state if too much.
But it has been a while since I experiemented with stab trim, as when I found out it didnt work well to change, I stopped and used the same trim always, just moved my feet instead, or mast position, to keep the "good feel" when carving

Small rear wing shim changes no problems though, for finetuning

PF

[neilhapgood]

to shim the fuselage do you simply put something in the fuselage cavity, towards the front (?!), before dropping it onto the mast?

[Brizair10]

I like both,
with the shim the onda seems to glide a bit better through jibes an is more stable at Speed, shimless is a more lifty, pumpy feeling and probably better for slow waves....
it´s nice to play with tuning options...

[Mossy 757]

to shim the fuselage do you simply put something in the fuselage cavity, towards the front (?!), before dropping it onto the mast?

Yup!

https://www.youtube.com/watch?v=mVdSx5eNdUA