I am a total nube to using fiberglass. I just bought an old 80's Hobie 16. Turns out that beaching it for 20 years has completely worn down the bottoms of my hulls. I'm talking a 2 inch crack thru the glass. I was thinking I could fix it using fiberglass tape and some type of epoxy to add a few layers of extra material on the bottom. I don't really care what it looks like right now, in the future I may paint it or attempt a gellcoat. I have 2 questions: 1. Is this the wrong way to go about the repair? 2. What kind of epoxy would you use? I'll try to get some pictures of the damage up ASAP

WEST Epoxy w/ 2" ... 4" ... 6" wide fiberglass tape also available from WEST ... Sandpaper ... orbital sander and "elbow grease".

Harry Murphey
TheMightyHobie18/ P19MX

Would Kevlar tape be any better than glass tape, ie. last longer, or would that get ground down just as quickly?
I've got to do the same repair on a Prindle. I was thinking of using Kevlar but will it work with the same epoxy (West) or do I need something special, or am I wasting money on Kevlar?

I would think west would work as well with kevlar as glass. The problem I think with kevlar is if you wear away the resin and expose the cloth then it will fuzz up quickly. That is mainly if you sand down to far (which is kind of what you are doing beaching it all the time also)

An outstanding, easy, and less expensive option is to properly repair the boat with what it was built with: Polyester resin, glass, with a layer of gelcoat. The problem with using epoxy is twofold:
1) Gelcoat will not properly cure over some epoxies.
2) It's more than double the cost of polyester.

You don't need the bonding ability of epoxy for this type of repair, just fix it properly and gel coat. For a good primer on f-glass repair go Here.
Scroll to page 14.

or Here.
Scroll to page 16.

The reason I was thinking of using epoxy was because I had heard it was harder. Being the bottom part that skids on the beach/rocks, do you think it is better to use epoxy, or just use multiple layers of glass tape to get back what has been worn down? I'm definitely going to want to attempt a new gellcoat as I have identified some other repairs today when I looked at it. I'll put some pictures up asap.

oh ya, also, I've decided to use 3" glass tape, it looks like it should be plenty wide enough for my h-16

I too was thinking Epoxy for hardness, I am not going to try to gel-coat it afterwards, I am more interested in strong vs. pretty, it's not a race boat, just a beater.

in my experience polyester is harder

you can usually just dig a finger nail into sun warmed epoxy but you never can into polyester

epoxy is the best for wood, it's easier to mix, the chemicals aren't as dangerous and the fumes nowhere near as bad

but for repairs to polyester boats polyester bonds better, is harder and cheaper

keep in mind the polyester reaction requires a "Kick" from a small toxic catalyst and that the surface chemical left over from the epoxy reaction inhibit this kick

so if someone does a small epoxy repair to a normal polyester boat but later wants to spray new gelcoat over it the gelcoat over the epoxy won't cure correctly if at all

The WEST Epoxy bonds better to the "cured polyeser" then "new polyester" does ... according to the research I've seen. The issue of getting Gelcoat to bond to epoxy is the "Amine Blush" ... and you need to have "wax additive in the gelcoat as gelcoat is made to cure in an AIRLESS enviornment Ie: in the mold. With out wax and exposed to the air ... gelcoat never cures completely but will remain slightly "tacky".

The "Amine blush" issue is solved by allowing 3-4 days curing time before gelcoating w/ UV exposure ie: sunlight.

Now you will need several layers of cloth ... if you wish to apply the epoxy w/ cloth in one continous process I would start w/ wider cloth and work towards narrower cloth. Apply epoxy let it tack up ... apply a layer of cloth,and smooth out ... apply a coating of epoxy ... let tack up ... apply next layer of cloth ... etc etc.

Now if you have time you can work from narrow to wide cloth, but this requires allowing the epoxy to cure completely ... sanding ... next layer ...

I've done this more then once ... and if you are racing every weekend you get good at doing quick/fast processes.

Harry Murphey
H18mag/P19MX

I forgot to mention that you must remove the "Amine Blush" before gelcoating ... the post just above mentioned "surface chemical" ... that is the Amine Blush.

Wash the repaired area w/soap & water using a stiff brush to help remove the "Amine Blush" ... its saves on sandpaper and "elbow grease".

Harry

On my old A class this season I applied fibreglass tape and wessystem along the entire bottom of the hull which I didn't paint. It works fine but its not as tough as paint and abrades away with movement on sand leaving light scratches which would be slow for racing.
regards

Yeah...keep going...keep going...what do you do next if this were a repair on Will's Hobie 16? What do you topcoat it with to make it look nice and to keep the water out of any open fibers?

Its always good to stay with what the boat was made out in terms of chemistry and construction.

If you use Polyester, work outside, wear gloves. Long sleeves, long pants, and a mask are all good precautions. And dont smoke while doing the repair, its flammable.

Here a blurb from US Composites on Polyester Resin.

Polyester Material Info:
Polyester resins are the most commonly used matrix in the marine and composite industry. These resins are styrene-based, flammable and catalyzed when combined with Methyl Ethyl Ketone Peroxide(MEKP). When working with these resins in large projects it is advised to use gloves and a chemical respirator to protect yourself from the fumes. These resins can be used with any type of fiberglass, carbon fiber or kevlar, as well as used over urethane foam and other sandwich core materials. These resins tend to be fairly rigid when cured and also more brittle than epoxy resins.

http://www.shopmaninc.com/polyesters.html
http://www.shopmaninc.com/pdf/MEKPDirections.pdf

Epoxy

Room cure type epoxy will soften in the sun, but the surface temp needs to be over 120 deg F for West and 140 for MAS, so the bottom of the boat isnt going to get that hot, unless you leave the hulls sitting on the black pavement and then stress them in some way you could be in trouble, not likely.

If you use Epoxy, I recommend MAS, the slow hardener is no blush, and they make a no blush fast. Epoxy isnt as toxic, but you need to be more precise in mixing and measuring it. Wear gloves, dont get the hardener on your skin. MAS is low VOC so you dont need a mask. Work with epoxy in a dry, 70deg area, like a nice day in the shade, or a garage. Uncured epoxy doesnt like moisture, so evening dew, or fog could mess it up.

I use peel ply on all my repairs, it goes on top off the last layer that you are leaving to cure, and it peels off after the area is cured, it helps keep everything held down nicely, and it lets you squeegee the fiberglass down and get the repair nice and smooth. Fiberglass gets realy slippery when its wet out with resin, and its hard to keep it straight, plus the fibers come off easily. Peel ply makes it less of a mess and make it easier to work the cloth and get it all smoothed out nicely.

If you use Peelply, the amine blush forms on the outside of the repair, so when you peel the ply off, the blush comes off. No washing the blush, which is a pain in the ***.

Bill

Will
I dont think Epoxy is materially harder or softer than other resins. Its just differient chemistry.

Most stuff made professionally out of epoxy, like Hall Masts, Forte beams, etc, uses an epoxy resin that requires heat to cure it. The Forte stuff is cured in an oven at 300deg F, and Hall uses an oven too. Since thats not feasible for the homebuilder, West, MAS and others sell epoxy that room temperature cures. The downside is that room cured epoxy gets soft at between 120 and 140 deg F. A black part left in the sun, in TX on a hot day will get to 160 deg F, and according to Tony Delima at MAS, you want a TG of 40-50 deg above the working temp of a part, so room cure epoxy wont work for black parts that have to work in the sun. Now, if you cool the part down in the water (like a rudder) and then stress it you should be fine, but its something to keep in mind. A white part can get to 130 deg, so painting your part keeps the temp down quite a bit.

Also the first time an epoxy part is first heated at an elevated temp, it goes through a secondary cure, so you get a higher TG if you leave an epoxy part in the sun, or in your car. I usually leave my parts in the sun to cure, or put them in my car to get a higher heat cure.

If you want to make a black part, and its going to need to be stressed in a structural way (like a beam) in the sun and you want to make it with epoxy, you need to use some of these higher heat cure hardeners like, Infucure HT, Anhydride, Dici, or Low tox. West's Proset line has higher heat property's but isnt clear, so you cant make a black carbon part with that stuff.

I havent gone the route making an oven, Im toying with getting an old oven and putting it in the garage for small parts.

Steve Clark build an oven out of plywood and electric baseboard heaters some thermocouples. Its not that far outside of the basement builder's reach.

Sorry for draining the pond on that answer, but I was just talking to Tony about this yesterday, so its still fresh.

Bill

I've done both paint and gelcoat ...

Painting is faster and easier ... but is a thinner barrier coat and "Hobie Beach Landings" wear through it quickly ... w/ the fine NJ/Md beach sand here the first land can be enough.

Gelcoating: Gelcoat provides a much thicker barrier coat but is more difficult to use. Most imprtantly you MUST get the Gelcoat w/ the wax additive!!! You can brush it on and sand it down or you can thin the gelcoat and spray it on. For the bottom I would be inclined to brush it on ... you will need to sand out the brush strokes (Wax on/Wax off Daniel-san ... a far amount of sanding)but the thicker coat is what you want... If you spray it on the biggest problem I had was "little brown spots" that never cured ... took me awhile to realize it was "compressor oil" from the compressor coming through the airline ... you need to use "airline filters", a compressed air "dryer" is really nice if you have a shop that well equiped! I haven't tried one of those "electric sprayers", they may work well ... I just don't know.

Sanding: start w/ 180grit wet/dry to cut of the wax ... next 200grit... 320 ...400 ... 600 ... 800 ... 1000 ... 1200 ... 1500 ... 2000 and finaly 2500 ( if you want to take it that far) ... buff and wax. You will have a surface smoo...oooth and fast ... it will have a translucent shine that is beautiful. Most people stop at 600 grit but it will not shine and have the translucentcy. You can get the wet/dry sandpaper at a "professional" Auto Body suppy Distributor. ( the principles are just like one of those beautiful paint jobs on a "custom car")

Harry
H18mag/P19MX

Hey Harry
Is this what youre talking about.

epoxy


paint

AHhhhh ......

H-ll NO!!!

Where's Karl's avatar when you need it ...

Harry

Hi there,

There seems to be some myths about epoxy. True is that, there are three main disadvantages:
-You have to keep the mixing ratio exactly
-The ambient temperature has to be high enough (typically 15°) while epoxy is curing
-It is expensive

On the other side:
-no osmose
-much tougher than any polyester resin or gelcoat (no hair cracks anymore)
-can be used as gelcoat as well
-usable with high quality fibres as kevlar.

If you use polyester, the resin will always fail before the fibres at very low stress. However, it is sufficient for normal usage of beach cats. Epoxy allows to use the full potential of fibres and it has more abraison resistance.
I never had the problem with sticky epoxy due to sunshine. Cold hardened epoxy is stable until about 60°C. Shouldn't be a problem until you paint your boat black.

However I would choose polyester and glas due to the easy handling. If you have a good workshop (closed, not to cold), there is no other disadvantage than the costs, but the boat will definetly be stronger. I would not use kevlar, it is simply to expensive.

Cheers,

Klaus

A story and then some pointers

The first time I worked w/ polyester resin my father and I were working on the Family's cabincruiser ... we figured we needed a gallon to redo the cabintop ... it came in (4)qt cans w/ (4)tubes of Hardner ... seemed easy enough (1)gt resin to (1) tube hardner ... we mixed the hardner into the qt can of resin ... (2) minutes later the can started to "smoke" ... a minute later the qt can was too hot to touch ... a minute after that we had jelly ... a minute after that we had a "SOLID" can of resin ... we scratched our heads and said ... "maybe we should ask some questions" ... we laugh about today ...

1) Buy the "mixing pumps", it takes all the quess work out of the mixing the epoxy. Stir/mix it well before applying

2) Get some shallow pans ... for epoxy I find the plastic "microwave diner trays" work best ... get several. The shallow pans do not allow the heat in the reaction to build up

3) On very hot days "chill" the epoxy and pans in refrigerator before starting Note: Do not allow wife/girlfriend to see pans/epoxy in refrigerator ... you will be in trouble!!! Mine did not see the humor in it!!!

4) Mix small batchs ... usually (4) pumps is all I can apply at a time before it starts to "kick". Rotate pans and discard brushs as required. If you are using a roller to apply then you can mix a larger batch ... for larger batches I use a "icebath" to extend the "working time".

5) After the final cloth application and sanding I will apply one more coat to resin w/ NO thickeners and the sand carefully so as not to expose any cloth fibers.

Do not forget to use disposable gloves ... you can by boxes at a "medical supply" cheaper then at the "marine supply".
I'm afraid someday I will pay the price for all the baths I took in solvent, acetone ...MEK ...

Hope this will help get you started

HarryMurphey
TheMightyHobie18/P19MX

PS: NO BONDO!!!