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| Nylon Bolts http://www.hobie.com/au/en/forums/viewtopic.php?f=71&t=54729 |
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| Author: | Sundance [ Thu May 14, 2015 4:36 am ] |
| Post subject: | Nylon Bolts |
Are the Hobie nylon bolts anything special? I have bought spares at the local hardware store and I'm wondering if it' okay to use them. I've found the same size bolt in black and white. Is there a strength rating for nylon bolts? |
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| Author: | mmiller [ Thu May 14, 2015 8:43 am ] |
| Post subject: | Re: Nylon Bolts |
Nothing specific that I am aware of. |
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| Author: | Tom Kirkman [ Thu May 14, 2015 9:23 am ] |
| Post subject: | Re: Nylon Bolts |
The only possible problem I can foresee is that there are different vendors that all make nylon fasteners. Hobie has selected one that satisfies the criteria for use as the sacrificial bolt in that system. There is the chance that the one you buy at the local hardware store may be weaker (or stronger) than the one supplied by Hobie. Then again, they could be exactly the same. Point being that lower grade hardware componentry isn't rated for nor held to any particular standard. It's not quite like buying a grade 8 aircraft fastener. |
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| Author: | Chekika [ Fri May 15, 2015 5:05 am ] |
| Post subject: | Re: Nylon Bolts |
Sundance wrote: Are the Hobie nylon bolts anything special? mmiller wrote: Nothing specific that I am aware of. Personally, having a 2015 AI Hobie aka brace shear pin break in open water for no apparent reason does not give me any confidence in the quality of Hobie shear pins. Everyone who does adventure trips (camping, off-shore fishing, Everglades Challenge, etc) should have "safety lines" to prevent collapse of the aka/ama in the event a shear pin break. My version of safety lines can be seen at http://www.hobiecat.com/forums/viewtopic.php?f=70&t=7276&p=256156#p256156 Scroll down near the bottom of that page to see my discussion of my "Keep-Out" lines and the testing of them. Fusioneng's discussion of "safety lines" is also there. Keith |
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| Author: | Buckaroo [ Fri May 15, 2015 5:44 am ] |
| Post subject: | Re: Nylon Bolts |
There are many different plastic fasteners available that have different shear strengths even within a given material type depending on the formulation of the material. I have tried to find out if this fastener is even nylon. As far as I can tell everyone is just calling it nylon. Hobie has not stated that it is nylon in any post that I can find here. You have to start with what material it is, then know what formulation of that material it is in order to know it's strength. Just google "plastic bolt" and you will see what I mean. Hopefully the Engineering department at Hobie selected a specific fastener for this application that has a known shear strength and the purchasing department is still buying the fastener that was specified. If you knew what is being used currently then it might be possible to select a slightly stronger fastener rather than substituting something that is too strong like stainless steel. Or, possibly just substitute a fastener of the same material that is not threaded along it's entire length. If you replace the shear bolts with something from a big box store you have no idea what you are getting. Why bother, they are not expensive to purchase from Hobie and at least you know what you are getting. I have had several experiences with poor quality metal fasteners from big box stores, I think it's probably safe to say that the plastic fasteners are no better. I wouldn't use the boat without ama safety lines. Just my $ .02 worth Chris |
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| Author: | fusioneng [ Fri May 15, 2015 7:01 am ] |
| Post subject: | Re: Nylon Bolts |
Tom Kirkman told us he replaces his nylon sheer bolts on a regular basis (which is the wisest thing to do), I discovered in testing recently, that each time the AMA takes a small hit (usually during launching and retrieving), the bolt deforms slightly (starting with the threads getting buggered up). The nylon bolt then becomes a ticking time bomb, where each small hit deforms it just a little more (might take a yr or two of repeated small hits to eventually fail). Eventually it will give when you least expect it (like what I suspect happened to Keith during his now famous capsize). In my case, I'm very safety conscious, and added the little safety rope thingy so if and when that nylon bolts does break (as it's designed to do in a collision), there is no surprise folding in of the AMA, and I don't capsize and go swimming with the sharks. I'm a design engineer by profession and recently studied the effects and results of the AKA brace system, because of the location of the brace, any forward or backward force applied on the AMA is tripled at the aka brace joints. To test this you only need a fish scale and measure the loads yourself. With the the brace locked out, simply push the AMA forward and backward with light force, you will see the entire side of the hull flexing like crazy under the load (because of the leverage). The amount of force required to fold (what we are calling elbow) the metal AKA bar tube appears to be around 400-600 lbs. and the amount of force required to shear off the big ball on the hull also appears to be around 400-600 lbs of force. Since the force on those joints is tripled from actual force applied. If the AKA brace were rigid (like with a stainless bolt instead of the normal nylon sheer bolt, as some have done). it takes around 200 lbs of force applied to the AMA (basically the weight of the boat) (ie... 200 x 3 =600 lbs), to fold and elbow the AKA bar, or knock the ball off the hull, (or tear the hull) either if which are major structural damage and are not recoverable (your done sailing that day, and have to order new parts). In my opinion it's best to just leave the original design alone (it a wonderful well thought out design) with the shear bolt, where in the event of a collision, it just snaps and allow the AMA to fold in harmlessly (no damage to the boat structurally). With the only downside being if the AMA were to fold it, you will likely capsize, I simply left the original system in tact, and added a simple secondary redundant rope thingy to prevent the AMA from folding in completely until I can furl my sail and make repairs (replace the shear bolt). Currently the shear bolt breaks when around 100 lbs of forward or backward force is applied to the AMA (tested with a fish scale), which is half the structural limit of the structure (which is 200 lbs as explained above), personally I don't think I want that shear bolt any stronger than it is currently for fear of seriously damaging my hull or critical structural components, the one's that are supposed to get me home safely. Hope this all makes sense Bob |
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| Author: | Totch [ Fri May 15, 2015 8:07 pm ] |
| Post subject: | Re: Nylon Bolts |
I agree with Bob (Fusioneng). After my scary dive trip in December, I just went and bought a bunch of Hobie sheer bolts from ACK and put them in my save-a-trip bucket; they're pretty cheap. I've done my own hardening similar to others here (just with cargo straps). The goal for me is for everything to just hold together until I can get another bolt in. I'm sticking with the Hobie bolts. |
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