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Mast support hull stud distorting hull
http://www.hobie.com/au/en/forums/viewtopic.php?f=75&t=52641		 Page 1 of 1
Author:  siravingmon [ Sat Aug 23, 2014 1:56 am ]
Post subject:  Mast support hull stud distorting hull
I notice that the nut on the stud in my new AI hull under the mast support is pulling the hull up in that area to meet the base of the plastic mast support, adding extra stress and strain to hull around the stud anchor area (see photo below - mast stud is to the right of the photo). The only way I can imagine fixing this would be to add spacers under the mast support base, but it's hard to get a good look at the area without taking it apart. Has anyone done this mod on a post 2011 AI? Should I be concerned about this or is a similar amount of distorsion in this area completely normal?
Image

Any suggestions much appreciated
Author:  tonystott [ Sat Aug 23, 2014 3:36 am ]
Post subject:  Re: Mast support hull stud distorting hull
Ideally you should get your dealer to do it, but if this is not convenient, and you feel confident enough, you could undo the lock nuts on the V-braces, and increase their lengths, evenly, and a little at a time. This will tend to push the mast base downwards. Check after each adjustment, you don't necessarily need to totally remove the indent. Don't forget to tighten the lock nuts afterwards.
Author:  siravingmon [ Sat Aug 23, 2014 6:25 am ]
Post subject:  Re: Mast support hull stud distorting hull
Many thanks for your suggestion Tony, but I'm afraid I don't understand how that can help with my issue.

Allow me to explain my point of view: on a 2014 AI, the plastic mast support tube and the V braces are both essentially anchored through to the X-bar at the top (so cannot move independently of each other at the top). The bottom of the V braces sit on top of the plastic mast brace and so also can't move independently of the mast support, meaning the V braces can't extend the depth of the mast support to relieve the tension in the hull floor (as I see it). Does my argument make any sense?

If the V braces acted directly on the hull floor I can see how they could push it down, but as it is the only solution that springs to mind to effectively make the mast support deeper and so relieve the strain on the hull stud area (due to it being pulled up to meet the mast support) is the one I mentioned of inserting washers between the underside of the mast support and the stud support area in the hull floor

Happy to be corrected if I'm wrong! :-)
Author:  tonystott [ Sat Aug 23, 2014 12:03 pm ]
Post subject:  Re: Mast support hull stud distorting hull
Simon, I perfectly understand what you are saying, having been involved in some rather warm (as opposed to heated LOL) discussions on the subject.

Of course you are correct regarding the "fixed" relationship between the mast holder and the crossbars, however, thre is a very small mount of "wriggle room" available which slightly stretches the mast holder due to it being connected to the crossbar only on one side. You might be able to push the bottom of the hull maybe 1/8 inch or so.

This will certainly not remove the hollow in the bottom of the hull, but could be done in concert with your idea of shimming the underside of the mast carrier with washers.

However, it should also be said that all rotomolded hulls like Hobies tend to exhibit some variations (unlike glass fibre hull) due them shrinking slightly as they cool after molding, so minor distortions such as on your Island are not reaslly criical.
Author:  fusioneng [ Sat Aug 23, 2014 12:49 pm ]
Post subject:  Re: Mast support hull stud distorting hull
Simon:
I wouldn't worry about it in the least. Think of the hull as if it was made of jello, it will conform to pretty much any shape it wants to settle into. If your concerned just sit the boat on flat cement in your driveway on a hot day and it will all settle back to the correct shape.
Actually having that area a little recessed is better than having it stick up, I've seen hulls where that area was scuffed up pretty badly from dragging on cement, where the hull had to be repaired. It's not going to affect the performance of the boat at all as gentle curves and dips don't affect the hull performance, only sharp edges and holes (like the mirage drive pocket) create drag.
Chances are the mast holder is in it's factory position, and the area around it is sagging (remember the hull is jello) has sagged due to possibly incorrect storage during some time in the boats life.
If you lay the hull in your driveway the correct shape is pretty flat to the ground thru the center part of the boat with the tip of the bow and stern sticking up a few inches (like 2-6 inches, the actual measurement isn't important). If it was me I would just leave it, not hurting a darn thing.
When I leave my TI mounted on the roof of my car sometimes for weeks at a time in the hot key west sun, it all distorts like crazy, I just lay the boat in the drive for a while in the sun and it all settles back to normal.
Hope this helps you
Bob
Author:  siravingmon [ Sat Aug 23, 2014 1:22 pm ]
Post subject:  Re: Mast support hull stud distorting hull
Thanks a lot Bob,

I'll leave it in that case, it was just those photos on the forum of cracks around the brass insert that made me think about this.

PS I read that earlier 'Mast Support Fail' thread with great interest :-)

PPS My mast support appears to be attached to the cross bar by 2 bolts sunk inside the cross bar with plastic access caps
Author:  tonystott [ Sat Aug 23, 2014 1:54 pm ]
Post subject:  Re: Mast support hull stud distorting hull
Yes, the two bolts hold the crossbar and nast support together. Evidently earlier versions were not bolted together like that, so I had some difficulty convincing people that depth of the mast receiver could not be easily adjusted by large amounts on latest vrsions.

I agree with Bob, and I wouldn't bother even trying to "fix" that hollow. When you see the turbulance generated by the drive well (even when fitted with th plug), it will be clear that the slight hollow will have no measurable effect.

Get out on the water and have a ball! :mrgreen: :mrgreen: :mrgreen: :mrgreen: :mrgreen:
Author:  Lumos [ Mon Aug 25, 2014 10:53 am ]
Post subject:  Re: Mast support hull stud distorting hull
My 2014 TI shows similar variations in the hull. While I would prefer a more robust hull, I suspect this is normal and characteristic in flatter areas in hulls made with polyethylene.
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