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Old 14-02-2012, 17:44   #1
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Fiberglass Chain Plates - Paging Minaret

polish of the stainless external chain plates revealed a few problem areas, rather then make new ones of those i think i am ready to tackle this once and for all...

the plan is to cut many *how many? 2.5" x 30" strips of fiberglass *what kind will be dicussed later, find a suitable bushing material with .5" id and cut into pieces 2.5" long...

wet out each piece of glass on a flat formica table, place on top up each other one at a time rolling out air bubbles each time.... once they are all stacked place the bushing in the middle and put in some epoxy thickened with cabosil next to the bushing to make the transition fold the glass over roll out the bubbles and let that cure....

clean it up, cut a slot to fit these http://www.colligomarine.com/Colligo...-1/2-Black.htm

repeat x8.... then i will bolt the to the hull with epoxy/cabosil and recessed head bolts then glass over the whole thing with a few more laters and fair it into the hull... fiberglass is forever for better or for worse

now for the details, minaret, this is where you come in barring some flaw in my previously mentioned plan...

how many layers of glass? im thinking 10+ , and what kind, i imagine unidiretional is best in this application? what about alternatiing uni and biax?
would like to avoid the expense of carbon fiber dont mind overbuilding the crap out of them with regular glass what says yee?
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Old 14-02-2012, 18:02   #2
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Re: fiberglass chain plates, paging minaret

I suppose you can get away with that on a 30 footer. My plates are 4 inches X 3/4 inch thick X 4 feet long and two per plate. I recently read an article in one of my sailing rags where the writer said there was surplus titanium on teh market for about the same as SS. No rust ever and may get you an insurance reduction.
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Old 14-02-2012, 18:10   #3
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Re: fiberglass chain plates, paging minaret

previous stainless ones are 2.5" x .25" ~ 16 inches long, chain plate for uppers is 6" wide because it is a pickle fork that stradles the mast supporting bulkhead, not exactly small, easy to accomodate in fiberglass... i dont doubt that i can make these strong enough

been hanging out on my friends 57 steel roberts and the rigging is soo big its stupid, cant even compare to smallish boats
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Old 14-02-2012, 18:18   #4
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Re: fiberglass chain plates, paging minaret

Yea, I've done a lot of integral glass chainplates. I'm used to a totally different setup than what you are suggesting, where we laminate the chainplate in place around a titanium "thimble" which is turned out of a blank of titanium rod. The chainplate is built before the deck goes on, and we wrap carbon uni's up one side of the hull, over the thimble, and onto the other side of the hull. The uni's are fanned onto the hull at opposing angles, each uni cut to a slightly different length, so the whole layup tapers out in all directions. This makes the most lightweight high strength corrosion free chainplate ever, but obviously isn't an option for a retrofit. I think your idea is perfectly viable, and have considered it before myself. The problems are several. First, you have no rated strengths backing you up on this, no solid figures saying X thickness of Y laminate will give you Z strength in a given plane. As a result it may be difficult to get a rigger/surveyor to sign off on such a setup. I would consider making a couple of trial pieces and destructively testing them to determine the true failure point, which might be more trouble than it's worth. Just the fact that it's a road not traveled means it may be more complicated for retrofit, but personally I wouldn't hesitate.
I make a lot of flat stock of various types for various purposes, and I think you're idea would be very easy to do nicely. I would consider a simple mold, perhaps even a press mold with a lid for this. Build a simple rectangular box out of MDF with precovered formica on one side, its a perfect ready made release. Once you lay out your tape, put the pin in the middle, and fold it over, put the whole mess in the mold. You can leave one end open for the pin. Then press a lid into the mold, perhaps to a stop if you want them all perfectly uniform in thickness and resin ratio. You could crank out a bunch that way, especially if you make two molds. You might use a proxy pin with a release on it, so the actual pin could be a press fit into the top of the chainplate, allowing you to remove and replace it if needed. I would bolt it in place just like a metal chainplate, using 4200 or Sika instead of a ridgid nonflexible material like epoxy. Then you don't have to fair them in and paint them, as long as they are external chainplates now. Or you could do as you suggest and fair them in, using countersunk bolt heads and glassing over. The problems I see there are that a chainplate strong enough to handle the load will be too thick to fair easily, unless you are doing this on a cored hull you are going to decore and do a solid blockout on. And countersinking the bolt heads will make the whole setup substantially weaker, requiring you to use even thicker plates. No, I think i'd do it just like metal plates, just they'd be thicker and painted instead of shiny. It would be fairly cheap to do yourself, if you have the time and facilities at hand for some R&D. I think it would also make a superior plate with a captured pin that you would never lose sleep over.
I'd do the whole layup with uni tapes. Find out what precut widths of uni tape are available to you before hand and design the whole thing around that dimension, it will save you a ton of trouble. Just trying to help you brainstorm here, happy to help bounce around any ideas. More people should consider this, and if you do it I'd love to see pics or help in any way possible, I may do it myself someday.
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Old 14-02-2012, 18:20   #5
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Re: fiberglass chain plates, paging minaret

This is foolish. Stay with stainless steel. You will be risking a lot if your GRP chainplates fail. Also, your boat will have a lot less resale value. You can have custom stainless steel work done by Stainless Steel Fabricators. See link below. Contact Jim Schoff. They have done lots of work for me and I have never been disapointed.

Stainless Steel Fabricators: Custom Stainless Steel, Steel, and Aluminum Fabrication
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Old 14-02-2012, 18:22   #6
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Re: fiberglass chain plates, paging minaret

Oh, not sure about the piece of hardware you linked too, it looks like it's for lanyards and deadeyes. I know some modern boats are actually going back to that setup, using spectra lines, but I don't know if that's what you're shooting for there. Enlighten me?
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Old 14-02-2012, 18:28   #7
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Re: fiberglass chain plates, paging minaret

thanks sam, i work in small (4 man) metal shop that does mechanial pipe work and all kinds of stainless work on superyachts exclusively, i could punch out stainless ones in a day there... i still want to do this , and am comfortable with my skills as this point to tackle it...

minaret - thanks will consider the mold but didnt really consider that since i want to glass them onto the hull, i when i sail fair i dont mean fair with the hull, they will be raised but smooth radiuses and glassed over, fair the rough glass work and paint im sure you can envision that?

going to try and get going on this this weekend...
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Old 14-02-2012, 18:29   #8
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Re: fiberglass chain plates, paging minaret

Quote:
Originally Posted by Sam Plan B View Post
This is foolish. Stay with stainless steel. You will be risking a lot if your GRP chainplates fail. Also, your boat will have a lot less resale value. You can have custom stainless steel work done by Stainless Steel Fabricators. See link below. Contact Jim Schoff. They have done lots of work for me and I have never been disapointed.

Stainless Steel Fabricators: Custom Stainless Steel, Steel, and Aluminum Fabrication

Note that many modern very high end boats have integral fiberglass chainplates, it can be a much better option than SS plates. All the big racers have them. SS plates are kind of old hat in the high end sail boat world. I would worry much less about things like crevice corrosion and fatigue failure in a well built glass chainplate than in a SS plate. This is a totally viable option, that most don't pursue. A manufacterer can afford to do some destructive testing and prove the ratings on their setup, so it's no big deal on a new boat, surveyors love it there. But as a retrofit, it would require time and effort to prove the setup first. At least I wouldn't just guess. Perhaps we need to develop a line of custom made pre built fiberglass chainplates for sailboats retrofit market? Wonder if anyone would buy them...
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Old 14-02-2012, 18:30   #9
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Re: fiberglass chain plates, paging minaret

yup trying to pinch my pennys for synthetics...
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Old 14-02-2012, 18:34   #10
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Re: fiberglass chain plates, paging minaret

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But as a retrofit, it would require time and effort to prove the setup first. At least I wouldn't just guess. Perhaps we need to develop a line of custom made pre built fiberglass chainplates for sailboats retrofit market? Wonder if anyone would buy them...
was just thinking about the same thing myself... as synthetic rigging gains traction, and it will, that shttuufff is the future, so will this kind of stuff,

i had never thought about looping the fiberglass over the hull laminate on both sides, added to the list of details for future dream boat
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Old 14-02-2012, 18:42   #11
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Re: fiberglass chain plates, paging minaret

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Originally Posted by minaret View Post
Perhaps we need to develop a line of custom made pre built fiberglass chainplates for sailboats retrofit market? Wonder if anyone would buy them...
Sounds like it would be a product liability nightmare.
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Old 14-02-2012, 18:43   #12
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Re: fiberglass chain plates, paging minaret

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Originally Posted by pressuredrop View Post
thanks sam, i work in small (4 man) metal shop that does mechanial pipe work and all kinds of stainless work on superyachts exclusively, i could punch out stainless ones in a day there... i still want to do this , and am comfortable with my skills as this point to tackle it...

minaret - thanks will consider the mold but didnt really consider that since i want to glass them onto the hull, i when i sail fair i dont mean fair with the hull, they will be raised but smooth radiuses and glassed over, fair the rough glass work and paint im sure you can envision that?

going to try and get going on this this weekend...
Absolutely, makes perfect sense. In retrospect, are these straight plates that you can lay up in a mold or on a table, or do they need to be curved and hence laminated in place? Do they bolt through the hull or through a bulkhead? External or internal? I would still mold them if flat, just to have uniform width and length and thickness. Without a mold the layup will want to fan out on a table. Only a very simple mold is needed, not a "finished" mold. I'd use uni tapes, alternating S-glass and carbon, for the whole layup. Biax will go all wonky on you if you cut it that narrow, it's a PITA, I've had to do it because the chem. engineers laminate schedule called for it before. WR ends up losing all the weft and being just warp, hence essentially a uni that sucks to work with when cut that narrow. Only the uni strands are adding the needed strength anyway, though some diagonals from the DB don't hurt. It's a lot easier to get the DB to lay down right in a mold as well, but I still wouldn't use any. Don't use any carbon for the outside lams, since countersinking the bolt heads will make them fairly useless anyway, bury the carbon in the middle of the lam. A mold with a lid which clamps down to a stop will also help you to make a very lean laminate, hence much stronger, by squeezing out the excess resin. A setup like this can give you resin ratios in the 35%-40% range, impossible to acheive any other way except bagging. Thats how they make G10, in a 60k lb. hydraulic press. And it's way stronger than steel. It'll also help you keep tension on the strands around the pin, resulting in a layup with superior fiber orientation. JMHO.
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Old 14-02-2012, 18:47   #13
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Re: fiberglass chain plates, paging minaret

Would love to buy some titanium chain plates if someone were to figure out how to tool them for a reasonable price...
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Old 14-02-2012, 18:56   #14
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Re: fiberglass chain plates, paging minaret

allright well now youve got me sold on a simple mold... chain plates are external on the outside of the hull... the transom plates with need a curve in them because of the transom angle, they can all be made on a mold in the shop, no need to laminate in place...
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Old 14-02-2012, 18:56   #15
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Re: fiberglass chain plates, paging minaret

Something you should be aware of here. The chainplates need to be strong enough to to have a fatigue strength sufficient for a really large number of cycle. Every wave the boat sees is going to add a stress cycle to your plates. Gougeon Bros did some fatigue strength testing on polyester glass and measured an 83% reduction in strength from a fairly small number of cycles, as I recall they estimated it was what a boat would see in about 3 months.

So, a few points:
#1, the chain plates need to be a lot stronger than just the loads they will see. Typically they'd be designed to fail at maybe 1.5X the breaking strength of the wire. With glass, make that number a lot bigger. I'll give you a comparison - on homebuilt aircraft, using metal construction, the typical safety factor over the max load the aircraft is rated for is 1.5. That is a really low safety factor which works because of careful engineering, design and maintenance. On homebuilt fiberglass planes the safety factor is commonly 5x to 10x the designed load on something like the wing spars. Partly because it is very hard, at a built at home level, to make a fiberglass layup that is anywhere near as consistent in strength as is metal. So make them really strong. And as Minaret said, forget the recessed bolts.
#2, make the layup with epoxy. And not just any epoxy, a high strength, structural grade. This is NOT WEST, etc, they are designed for glueing up wood. If you don't use the good stuff, and you can't buy the good stuff at local retailers, then again make them bigger to compensate.
#3, the moral of all the above is that there are a lot of variable which are not practical to determine. So you do what engineers do - the larger the unknown factor, the larger the safety factor. The less you know about what you're working with, the more you overbuild it.
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