Recently got a Cabrinha hirise varial M and the first day I was using it wake foiling, the fuselage came off. When the new one arrived I was surprised to discover that the screws holding the fuselage to the mast only protruded 8mm of thread. Did some searching and found that for aluminum, the thread depth should be 2 times the bolt diameter. So the 8mm bolt should go 16mm into the mast by industry standard. I have a picture of me crashing and the foil actually came off in the water. I did not hit anything while foiling along either. Anyone else have this problem?

Heard of and seen bolts break and fuse fall off... but never bolts pull out.

... you did put the right bolts in the right place? Or did you receive it assembled?

Check the bolts in the plate and see if they're really long.

The bolts were in the right place. Longest ones provided were 40mm for the top and bottom of the mast. Odd though that the top bolts that hold the mast to the mounting plate thread in over 20mm while the same 40mm bolt that holds the fuselage to the mast only threads in about 7mm. The Fusleage mount is obviously much thicker than the base plate. For aluminum it is suggested that the thread depth should be twice the bolt diameter. That means that the threaded hole for the 8mm bolts should be at least 16mm deep, like on the top mounts. I am thinking it is a design oversight and that the fuselage was meant to have a deeper recess for the mast, something got changed so it became shallower, and the bolt length was not changed to compensate.

Buy some longer bolts, but even 16mm thread use is not enough.
30-40 is good
the more the bolt is in mast the better

Thanks. I did buy some longer ones for the new foil. 50mm I believe. I am just checking to see if this is a common problem so I can get some information to approach Cabrinha with, to get my new foil on a warranty.

Exactly the same problem for exactly the same foil kit. In just 6 sessions, from new (no hit in anything etc) i lost the fuselage. Although i had everytime tef-gel applied, as a best practice, both bolts got loose. The end result, apart from loosing the complete fuselage/wing part, was to have the half length of the mast threads, weared of. THe local dealer didn't accept to replace it under warranty, saying that this is my word without any proof of loss (oook). Given that i was very satisfied with the wing, i accepted an offer for a new wing at the cost. I guess that it should be covered from the warranty, given that this is obviously a design problem, hence i will write to Cabrinha for the incident. BTW the new foil, after 15 minutes of first use, the bolts got loose again. Now i don't know if i will follow your way you delt with the problem, or weld it permantly.

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windmachine said..
The bolts were in the right place. Longest ones provided were 40mm for the top and bottom of the mast. Odd though that the top bolts that hold the mast to the mounting plate thread in over 20mm while the same 40mm bolt that holds the fuselage to the mast only threads in about 7mm. The Fusleage mount is obviously much thicker than the base plate. For aluminum it is suggested that the thread depth should be twice the bolt diameter. That means that the threaded hole for the 8mm bolts should be at least 16mm deep, like on the top mounts. I am thinking it is a design oversight and that the fuselage was meant to have a deeper recess for the mast, something got changed so it became shallower, and the bolt length was not changed to compensate.

That's bad. Fuse to mast bolts are the long ones, should be like 70mm. 7mm won't hold anything. Someone in the supply chain has messed up big time, and that's on the shop for making sure it was fit to go out the door. I'd take it further.

You're saying the mast only has 7mm of thread cut into it inside the holes?

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Chris22 said..
Exactly the same problem for exactly the same foil kit. In just 6 sessions, from new (no hit in anything etc) i lost the fuselage. Although i had everytime tef-gel applied, as a best practice, both bolts got loose. The end result, apart from loosing the complete fuselage/wing part, was to have the half length of the mast threads, weared of. THe local dealer didn't accept to replace it under warranty, saying that this is my word without any proof of loss (oook). Given that i was very satisfied with the wing, i accepted an offer for a new wing at the cost. I guess that it should be covered from the warranty, given that this is obviously a design problem, hence i will write to Cabrinha for the incident. BTW the new foil, after 15 minutes of first use, the bolts got loose again. Now i don't know if i will follow your way you delt with the problem, or weld it permantly.

Something's messed up in production here and the shop needs to step up and provide the service they claim justified their prices.

What length are the new bolts? How far up is the hole threaded? How snug so the bolts for the threads?

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Kamikuza said..

Chris22 said..
Exactly the same problem for exactly the same foil kit. In just 6 sessions, from new (no hit in anything etc) i lost the fuselage. Although i had everytime tef-gel applied, as a best practice, both bolts got loose. The end result, apart from loosing the complete fuselage/wing part, was to have the half length of the mast threads, weared of. THe local dealer didn't accept to replace it under warranty, saying that this is my word without any proof of loss (oook). Given that i was very satisfied with the wing, i accepted an offer for a new wing at the cost. I guess that it should be covered from the warranty, given that this is obviously a design problem, hence i will write to Cabrinha for the incident. BTW the new foil, after 15 minutes of first use, the bolts got loose again. Now i don't know if i will follow your way you delt with the problem, or weld it permantly.

Something's messed up in production here and the shop needs to step up and provide the service they claim justified their prices.

What length are the new bolts? How far up is the hole threaded? How snug so the bolts for the threads?

The new foil kit came with 40mm bolts. In general the bolts aren't of good quality. They just melt in the allen head even when the minimal of the force is applied. In any case i replaced all the bolts with some excelent quality stainless steel ones. In this case tef-gel will not work, because the cut of the thread are much finer. In this case LOCTITE 55 works like a charm. 70mm doesn't fit, just hit an end in the mast. 60mm fits perfectly. Think that almost 40mm are in the mast now.

It is a shame such a great wing to be supplied with such poor quality bolts!

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Chris22 said..

Kamikuza said..

Chris22 said..
Exactly the same problem for exactly the same foil kit. In just 6 sessions, from new (no hit in anything etc) i lost the fuselage. Although i had everytime tef-gel applied, as a best practice, both bolts got loose. The end result, apart from loosing the complete fuselage/wing part, was to have the half length of the mast threads, weared of. THe local dealer didn't accept to replace it under warranty, saying that this is my word without any proof of loss (oook). Given that i was very satisfied with the wing, i accepted an offer for a new wing at the cost. I guess that it should be covered from the warranty, given that this is obviously a design problem, hence i will write to Cabrinha for the incident. BTW the new foil, after 15 minutes of first use, the bolts got loose again. Now i don't know if i will follow your way you delt with the problem, or weld it permantly.

Something's messed up in production here and the shop needs to step up and provide the service they claim justified their prices.

What length are the new bolts? How far up is the hole threaded? How snug so the bolts for the threads?

The new foil kit came with 40mm bolts. In general the bolts aren't of good quality. They just melt in the allen head even when the minimal of the force is applied. In any case i replaced all the bolts with some excelent quality stainless steel ones. In this case tef-gel will not work, because the cut of the thread are much finer. In this case LOCTITE 55 works like a charm. 70mm doesn't fit, just hit an end in the mast. 60mm fits perfectly. Think that almost 40mm are in the mast now.

It is a shame such a great wing to be supplied with such poor quality bolts!

So that's on Cabrinha then eh.

Tefgel will work, it'll just squidge out the end of the hole if you use too much. You need less than you think :D Unless you've got the thread pitch wrong :o

Yeah ditch the Allen head's for Torx ASAP.

Tap the holes out deeper? I cut down a 90cm mast and retapped the holes ... I think I had about 60mm depth on the thread cutter but the fuselage is about 20mm thick so I had enough depth.