SoCal Jet Boats
Tech Talk => Gelcoat / Paint / Fireberglass Repair => Topic started by: eastcoastboys on January 15, 2016, 10:19:51 AM
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So I am gonna be replacing the floor and adding stringers to hang the four point motor mount system in this sleek craft SST hull. I can't find any advice anywhere on what type of fiberglass I should use. Matt vs woven vs weight. I have done my fair share of reading on fiberglass work and get the concept but have yet to really nail down what is best for my application here. Any input on how many layers and what weight and type of glass should be used and how far the new should be over lapped on to the old would be great.
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First, I strongly recommend cutting at least a 1/2" radius with a router on the top edges of the stringers. Jarvis's post ( my basket case
http://www.socaljetboats.com/index.php?topic=23445.msg277661.msg#277661) about mixing your own fairing material of resin and microsphears ( http://revchem.com/products/additives-fillers/) to build inside corner radii between the new wood of the stringers and the existing hull. You need these large radii so that it is easier for the new glass to conform to the surface and to prevent stress risers.
Using 12.5oz +/-45 (http://www.fibreglast.com/product/saertex-450-gm2-stitched-biaxial-fiberglass-2805/Stitched_Fiberglass), I would tab in the entire vertical surface of the stringers up to the radius and out 3"-4" into the original hull. Follow this up with another layer of +/-45, this time, wrapping over the top of the stringers and extending another 3"-4" beyond the first layer. I recommend laminating smaller sections rather than trying to do an entire stringer at once. Overlap the sections by 2" minimum so the strength of the strands is continuous. Stagger the overlap areas so you don't get huge bulges. Use laminating resin for this stage.
If you want your floors to be really nice, cover the +/-45 with a layer of 1.5oz mat. This is not an option if you are using epoxy resin. Mat contains a styrene binder to hold the strands together and is only compatible with polyester and vinyl ester resin. Sand the mat layer to blend and smooth the surface. DO NOT sand into the layers of +/-45, this is where the strength comes from. If the strands of the +/-45 are compromised from sanding, stresses will not be properly transferred from the stringers into the existing hull. The mat is there as a filler to build up low spots. Add more layers of mat to build up low spots rather than sanding through the +/-45. Use finishing resin for this stage because it will be sanded before the final lamination.
Lastly, I would laminate one final layer of 6oz cloth over the whole thing. Extend this layer 2" minimum beyond all previous layers. 6oz cloth wets out super easy. For this layer, I would mix some microspheres into the resin. As the resin cures, it will shrink and pull away from the fibers and the texture of the glass will show through. To reduce this, the resin can be thickened with a filler. The more filler you use, the more difficult it will be to saturate the glass, but the less shrinkage. Use laminating resin for this step.
To put a nice glossy finish and to seal everything, brush on a thin layer of finishing resin, clear gel coat (http://www.fibreglast.com/product/Clear_Gel_Coat_just_gel_coats_00180/Polyester_Resins), or gel coat with the color of your choice. Note: The gel coats will provide UV protection that the resin will not. Thin with styrene thinner (http://www.fibreglast.com/product/Styrene_Thinner_70 Polyester_Resins) and add the appropriate amount of styrene wax (http://www.fibreglast.com/product/Styrene_Wax_71/Polyester_Resins). Thinning will promote flowing out and will reduce brush marks.
Some thoughts on resin:
All resin degrades from UV radiation exposure. Epoxy is affected the most. If you insist on using epoxy, your top layer should contain UV protection. Do not add UV protection to every lamination as the additive degrades the resin's properties.
Polyester will NOT adhere to epoxy!
Epoxy will only achieve a mechanical bond to polyester, not a chemical bond. The greater mechanical bond of epoxy and its higher tensile strength can provide satisfactory bonds.
A lamination of vinyl ester resin can be applied between epoxy and polyester to achieve both a mechanical and chemical bond.
Polyester finishing resin is made by adding styrene wax to polyester laminating resin. You can also buy polyester finishing resin premixed.
It's all about surface preparation! No resin will adhere properly if the surface it is bonding to is not properly prepared.
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This sounds like your first attempt at glass work.
May I suggest that you practice laminating on some cardboard to get used to the resin and wetting out glass before laminating on your boat. Especially practice laminating into corners.
Focus on the following:
Getting complete saturation with no dry spots which will appear white and no puddles of excess resin. Voids, large air pockets, are bad news and need to be ground out and repaired.
Do not disturb the orientation of the fibers. The fibers are where the strength is. The strength of a laminate comes from the fibers pulling in tension. If the fibers can not pull in a straight line, not only do they provide now beneficial strength, they also create a stress riser.
Try to achieve a 50%/50% fiber to resin ratio (by volume) for starters. The resin is is there to bind the fibers together. However, the resin has a lower tensile strength than the fibers. The tensile strength of the finished product is an average of that of the resin and fibers. A resin-rich lamination has a lower tensile strength because the resin actually lowers the average. Also, resin is brittle and resin-rich areas will crack.
It is hard to judge exactly how much is a 50% resin to fiber ratio. I try to achieve total saturation (no white spots) while being able to see the texture of the fabric on the surface of the lamination. I remove as much resin as possible with a brush or squeegee, without developing dry spots.
Make every effort to work clean. Avoid inclusions, foreign object debris (FOD), getting into your lamination. Not only do they look bad, they reduce strength.
Get used to the tools:
At the absolute bare minimum, you will need a paint brush. Brushes used for laminating should have natural bristles and a raw wooden handle. Resins and solvents will attack synthetic bristles and plastic or painted wooden handles, contaminating your resin. What size brush is dictated by the area that you are laminating. I would start with a 2" brush.
Bondo squeegee, used for quickly spreading resin over large areas. The yellow plastic squeegees are great until you get a nick in it and it starts to pull the fibers out of their orientation. Any squeegee that is not kept clean will do the same thing.
If you want to get a roller ( http://www.fibreglast.com/product/Aluminum_Rollers_129/Supplies_Tools_Rollers_Squeegees),I would start with a 1/2" × 3" 129-A. A dirty roller will also pull strands. You don't need a roller to do this job, but it can help you eliminate air bubbles.
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A couple theories on laminating:
Resin kicks fast! To get the longest working time possible, keep the following in mind:
1. Using a metal bucket while working with resin will accelerate its gel time.
2. Resin will melt the wax in paper paint buckets, contaminating the resin. Only plastic mixing cups should be used.
3. Excessive or aggressive mixing of the resin adds energy to the resin and causes it to kick faster. It also creates air bubbles which requires additional work to eliminate from the lamination.
4. Higher temperatures and humidity decrease pot life, making resin kick faster. Lower temperature has the opposite effect.
5. A higher concentration of mass of resin, as is the case inside the mixing cup, will kick faster. Get the resin out of the bucket as fast as you can. I do this by pouring the resin out onto the surface or fabric which I am laminating. The thin cross-section of the lamination does not have the concentration of mass as in the mixing cup.
6. Mix the resin at the last possible second. Make sure everything is ready to go before pouring and mixing.
7. If you are using epoxy resin, there is a tolerance for the mixture of part A and part B. Part B is NOT a hardener or catalyst like Methyl Ethyl Ketone Peroxide (MEKP) is to polyester and vinyl ester resins. If that tolerance is exceeded, it will not kick at all. You can vary the amount of MEKP in polyester and vinyl ester to change its kick time (and properties).
8. Once the resin starts to gel, you are done working with it. If you try to continue, you will end up with a big mess. You will feel the resin thickening before it starts to gel. It will then turn to a Jell-O consistency, followed by a rubbery stage (green state), and lastly a hard plastic.
9. It is best to have two mixing cups. Mixing new resin in a cup that has gelling resin will cause the new resin to kick faster.
When laminating:
Wood soaks up a lot of resin I would apply resin to the wood first in the area that you are working. Then apply resin to the glass part of the hull. This gives a little time for resin to soak into the wood. After you have"wet out" the area where you will be applying glass, place the fabric over the wet resin and apply more resin. This saturates the fabric from both sides. The wood will continue to soak up resin. Be careful that a dry spot doesn't develop.
Learn to work the glass into the corners so that you don't pull voids.
Handle your fabric carefully so that the fibers are not distorted.
Keep your glass covered, dust settling on to it will prevent proper bonding of the fibers and cause a milky look to the finished lamination. Glass fibers will turn transparent when wet out but dust will turn white.
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Ok cool thanks for all the info and the links too. Perfect. One more question besides grinding with a sanding wheel the old glass in the hull and wiping it down before. Any thing else needed to make sure there is a good bond to the old. And how can I tell if it's not gonna bond cause it's not the same type
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Your hull is made of polyester. Degrease it really good first. Don't really like to wipe it down after. Acetone will penetrate oils into the crevices of freshly ground surfaces. I blow it off with clean/dry air.
Grind/sand with 36 grit. Any loose glass needs to be removed as does degraded glass and resin. Make sure no shiney surfaces remain.
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Sounds good! I have high faith in my self lol.
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Post pictures
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Oh definitely many to come.
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Wow.... good luck!!
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Flusher, your the man dude!! I was just looking for a post like this!! Thank you!!