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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #21  
Old 11-03-2009
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I hate to jump in to ask another question, but would there be an issue in using both plywood and glass?

Using just plywood - would you have an problem effectively "tying" the new core to the origanal core?
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  #22  
Old 11-03-2009
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Yes plywood could be used - the original builder did. But solid epoxy and fibreglass is I think the ultimate solution. Never again will it compress or absorb water as has happened to get us here. If the plywood is adhered properly and coated in epoxy totally it would work. I think it would take almost as long and be almost as expensive to do this with plywood as with biaxial and epoxy all the way through. The fairing, prepping for paint, and painting will take the longest - and you have to do this with plywood as well as all epoxy and glass. I think the goal is to fix it better than new, not necessarily copy what the builder did.
Brian
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  #23  
Old 11-03-2009
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Im sorry but i have been watching this and have wanted to ask this but was afraid of sticking my nose where it was not wanted...

Has any one ever thought of a using vacuum bag process and building a carbon fiber step assm and bonding it in? The best of both worlds, strong, light and tough as hell. I have made some rather complicated and large items in this manner.
A vac-bag step assm will be so compressed that air can not penetrate much less water .
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  #24  
Old 11-03-2009
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Quote:
Originally Posted by dieselboy View Post
Im sorry but i have been watching this and have wanted to ask this but was afraid of sticking my nose where it was not wanted...

Has any one ever thought of a using vacuum bag process and building a carbon fiber step assm and bonding it in? The best of both worlds, strong, light and tough as hell. I have made some rather complicated and large items in this manner.
A vac-bag step assm will be so compressed that air can not penetrate much less water .
Please stick your nose in...In short my answer is yes ,but with galss not CF.

Please walk us through the process on the cheap so to speak.
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  #25  
Old 11-03-2009
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Wow, the process is simple enough.
You build a rudimentary mold to make a part, figure out size shape and how you are going to mount, said part. Calculate how much strength you will want lay the carbon mat then pour in the resin.
slip a special bad over it and draw a vacuum with either an ac type vac pump or even a hand held brake bleeder pump.
The resin will cure in a vacuum and all the air in the structure will be drawn out. Leaving a VERY strong object. The Vacuum has the effect of drawing the layers very very tight.

2 layers of weave and a thin resin leave behind an extremely strong but quite thin part that is air and cavity free. I buy a bunch of stuff from a company called Max Bond while i am not here to push any product they do have a very good 4 min video on vac-bag process on a very low budget.

You will have to wade through the sales pitch but read up on the process and it will show one in action..
CARBON FIBER FABRIC 3K 2X2 TWILL WEAVE 6 OUNCE 50" WIDE - eBay (item 220500561712 end time Nov-24-09 16:02:23 PST)
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  #26  
Old 11-03-2009
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Ah, gotcha ...different train of thought...I was thinking more in place as in overhead vacuum techniques to suck everything up defying gravity so to speak.
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Old 11-03-2009
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Quote:
Originally Posted by Stillraining View Post
Ah, gotcha ...different train of thought...I was thinking more in place as in overhead vacuum techniques to suck everything up defying gravity so to speak.

While there would be a few challenges but if there we a hatch to got on both sides of it..... It could be done!
Super strong and air free.. Rather than pile on the glass and resin you could use Styrofoam as a filler or supports. As funny as that founds all F-1 cars use Styrofoam much in the way boat builders used balsa wood.
It could be done, i wish i were closer to this guy, we could do a few tests to see but i dont see why not.
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Hmmm...there again though your entering in a compressabal elliment where you do not want one...I would just like a quick clean way to vac any weard inplace profile with solid glass build up myself.

As an example..I would not mind adding 1/4" of roving or bi-directional to my whole hull...but adhering such a large area with quality is tough to do .
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Last edited by Stillraining; 11-03-2009 at 11:26 PM.
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Old 11-04-2009
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For the record, I can't think of any application in a boat where you would use plywood without glassing over it, even if it's just a single unit of 6oz to protect the epoxy barrier from abrasion like you see in plywood boats. In this application, the plywood provides an inexpensive core material to space the two laminates apart without any significant compressibility within the core material.

I haven't worked much with carbon, so I have a couple questions myself.
Would the weight savings be worth the cost of the material for this application ? I can see it if that's how the rest of the boat is built, but as a retro on an admittedly-inexpensive boat it seems like money better spent elsewhere.
What would be the advantage of carbon in this application ?

Dieselboy, if by 'Styrofoam' you mean blue- and pink-board, I gotta disagree with you. Yes it's used for body panels in many custom vehicles, but only where an inexpensive material is needed to hold shape. Using it as coring in a structural panel cause it to fail in long cracks that subject the glass to wicked shearing forces along a sharp line in the same place on the inner and outer laminates. If you can point me to a true unibody (structural) application that uses it for coring I'll happily stand corrected because it'll give me a lot more options in my own work once I figure out how they get the resin to saturate it...

Quote:
Originally Posted by mitiempo
Yes plywood could be used - the original builder did.
According to the OP, it was the fact that balsa core and NOT plywood was used for core that got him here. There are many (most?) production boats out there with plywood that never gives a worry as long as it's encapsulated. Plywood coring just doesn't fail without help - either through water ingress or mechanical damage.
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Old 11-04-2009
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If the original builder used balsa under a mast it was a mistake. The force downward of a mast rigged on a boat will guarantee a failure if this is (was) the case. Plywood is a step better but still compressable over time and when the compression occurs there will inevitably be at least hairline cracking that will allow water in. The water will cause rot because even if the plywood is sealed it will lose the integrity of that seal when enough force is applied to it (tight rigging trying to force the mast downward not to mention the sailing loads). If you're in a colder climate there is the freeze/thaw cycles which are guaranteed to open any hairline cracks further over time. If the skins were thick enough to prevent this over time there would probably have been no reason to use the plywood to start with as the skins would not in any way be in need of a core. Many boats by many builders were built this way and they are having problems 20, 30, or 40 years on. Cores work well if they are kept dry and not crushed by large forces. I don't believe that this is good engineering for all time, just for a while. As to carbon - it would be a waste of money in this case as it's only purpose really is to save weight - a square foot of glass/epoxy 3/8" or 1/2" thick can't weigh more than 5 or 6 lbs. The mast step doesn't have to be super strong on its own - just be non-compressable to transfer the force to the bulkhead or compression post below.
I don't believe that F-1 cars are built with styrofoam - in the crash testing videos I have seen it looked like a carbon fibre laminate without foam.
Brian
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