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Old 27-12-2010, 12:27   #1
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Fiberglassing-in Ballast - What to Use ?

I've searched and searched and can't feel comfortable with what I'm learning about which type of fiberglass to use to glass in the ballast of my boat. I have a Baba 35' with 1700lbs of aft ballast to glass in. What I'm thinking of using is 24 oz Biaxial Cloth 0-90 with T-mat Backing. However, I'm concerned that this will be difficult to work with in shaping it to the keel. Also, how much do I use and is this the only fiberglass I'll need to use?

Any suggestions or education you can give me on the matter would be greatly appreciated!

Karen
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Old 27-12-2010, 12:41   #2
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to be able to answer the question need to know how ballast has been placed in keel and what type,ie is it lead shot,punchings ,moulded lead/cast iron ?
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Old 27-12-2010, 13:37   #3
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ok i will assume the ballast is lead shot in a cold cure resin and has been poured into the keel aperture in the hull moulding,and has a realatively flat surface,also will assume aperture is 18 inches by 5 feet.

1st grind well alll surfaces to be glassed
2nd armosphere/micro ballons in about 3-4 kg polyester resin +1.5% catalyst to give a very sloppy mix.
3rd 1200g woven rovings cut to size with 2" overlap will need about 2-3 kg resin 2% catalyst
4th 450g chopped strand mat 3" overlap need about 1 kg resin 2% hardner
5th 450g csm 4" overlap 1kg resin 2% hardner
6th 450g csm 5" overlap 1kg resin 2%hardner

this should all be curing now,depending on the temperature of the hull,working on working times of about30- 40 minutes at 10celcius
7th gelcoat about 2 kg 2% hard ner
let cure 24 hours
sand off sharp points if any,key in surface
gelcoat 1.5 kg 2% catalyst

this will give you about a 6-7 mm layup
if thicker layup needed add extra layers of woven rovings and csm
obviously this technique of progerssive layupt is probably best done by a proffesional,as things can go very wrong if temp too high,or too slow laying up.

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Old 27-12-2010, 13:44   #4
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Ballast Material

The ballast is 50lb lead ingots. They are laid in epoxy and the sides/voids will be filled with 8lb pourable foam. The ballast was laid in the keel stacked, slopping. A picture is attached.

Thank you!
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Old 27-12-2010, 15:15   #5
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assume you mean 2.4 oz cloth,this is very easy to work with,but does not like 90 degree corners so would be best to have a rounded fillet or shape the foam filler above the lead.

also since you have allready used epoxy resin you will have to continue to use epoxy resin due to curing/compatability issues between epoxy and polyester resins.

it is a pity that you have used epoxy as polyester is a much cheaper option,and instead of pu foam it would have been better to fill voids with a resin/micro balloon mix thus creating a solid block of ballast,less likely to leak /get holed.
unfortunately pu foam is porous and does absorb water after a period of time.

nevertheless,would use a filler to fair on top of the foam and lead to give an even surface to glass onto.
then follow the steps in the last post.

ie filler/resin mix,woven rovings then chopped strand mat will give an even strong bond and bilge.
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Old 27-12-2010, 15:53   #6
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May sound dumb but... is there any reason one cant just pour concrete in there,,,, seen it in old boats from the 60's?
I mean... you want to fill the void and concrete aint gonna be any harder to get out the an epoxy/microfibre/balloon mix...
Just asking...
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Old 27-12-2010, 16:08   #7
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yes cement/fine sand mix would work. good thinking,would work better than pu foam,also then would be able to use polyester resin on top.
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Old 28-12-2010, 11:50   #8
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Biaxial Cloth +-45 with T-mat Backing?

This all helps tremendously. I think I have a grasp. Actually, I have not poured in the foam yet and I'm so glad. I'll finish filling with straight epoxy. The only reason I thought foam was to save some money and it was the aft section of the keel so I don't anticipate problems with running aground puncturing the keel or gouging. However, I love the idea of the comfort of one solid mass of ballast.

If I'm not mistaking, is biaxial cloth just as good or even better than laying up with csm and woven rovings? The only difference is cost and, of course, application method. For simplicity sake, I was thinking of going with 24oz (will be very stiff and maybe a little hard to work with but there wont be any tough corners) biaxial Cloth +-45 with T-mat Backing.
Thoughts?

Karen
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Old 28-12-2010, 12:53   #9
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Quote:
Originally Posted by boatman61 View Post
May sound dumb but... is there any reason one cant just pour concrete in there,,,, seen it in old boats from the 60's?
I mean... you want to fill the void and concrete aint gonna be any harder to get out the an epoxy/microfibre/balloon mix...
Just asking...
Concrete is not nearly as dense as lead. For the available space, he would not get the same increase in righting moment.

Concrete density - 145 pounds per cubic foot.

Lead density - 709 pounds per cubic foot.

Getting the CG of the lead slightly lower than the CG of the concrete would help lengthen the righting arm slightly helping the righting moment.
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Old 28-12-2010, 14:22   #10
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yes much better to fill up voids in the keel with a resin /filler mix although you have to be VERY CAREFUL about heat build up as the resin cures,dont fill too much at one time also use a slow hardner.

would not bother with the expensive bi axial cloth,as more difficult to get resin saturation though may be easier if you are a begginer.

once you have a nice flat base and have ground in the sides of the keel casing,i normally wet out with a thin resin/collodial silicon filler mix this fills voids and gives extra adhesion,work with a slow hardner in 1meter sections,hard work leaning into keel cavity.
with epoxy would use woven rovings then csm on top to give a nice smooth finish,this also fills any pin holes,so you dont get bilge water in behind it.

if you do use the biaxial would reccommend doing a test on a 90 degree bend on a work bench first.

i have used the biaxial cloth before but normally on large flatish hull mouldings.

remember you need about a 2" joint to the sides of the keel casing as well as on top of the lead.

will pm you if you need further info
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Old 28-12-2010, 14:43   #11
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Sorry David M.... just figured looking at the picture it would increase his self righting a lot more than PU Foam... I cant see what the difference is whether the concrete is higher or lower in the space involved.
If its around the lead more or less evenly and he glassed over that there should not be any difference,, bar a bit more ballast... I think...
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Old 28-12-2010, 15:13   #12
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the real issue is sealing the lead in place,a)from water leaking in from above,b)if the keel ever got punctured and c) holding it in place if the vessel ever did a 360.

i think filling voids was the issue,rather than stability factors.
if you have ever had to do a repair in a boat yard on a punctured or grounded grp keel,with water seeping out of it due to voids one would under stand the issues here.

once heard of a home built vessel that had used lead shot as ballast,though to save money hade not set it in resin,meerly glassed over the top.
any way went aground,a few months later found the yacht was getting very tender..........................
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Old 28-12-2010, 16:06   #13
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In looking at the bigger picture, if you placed the lead towards the bottom of the keel you would have much greater righting moment for the weight you are adding. By placing the lead where it looks like it is going to go, all you are doing is increasing the weight of the boat without increasing its righting moment much at all. Of course, a heavier boat could very well turn it into an overall slower boat. What's guaranteed is that you are creating a slower boat downwind and maybe a boat that is a tiny bit faster upwind.

Do you know exactly where your boats center of gravity is located? Because if it's close to where you are adding this weight, all you are doing is killing its downwind performance.
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Old 28-12-2010, 16:19   #14
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sorry david wasnt questioning your imput,which is quite relevant,i think this ballast is only for trim,looking more closely at the photo,rater than ballast,since it is in the skeg rather than the keel.

more worried about the stuff falling out and water tight integrity.
also the compatability of different types of resin and techniques of using it in situ.
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Old 28-12-2010, 16:30   #15
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Thanks, I was wrong about your goals then.
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