hull repair

i have what is a pretty good crack in my hull i have ground out the inside and i think i have found the crack if i glass over the crack 3 or 4 layers then grind from outside will it be ok covering the crack i tried to find some similar fixes on this site but hope someone can like par with experience can help

 

Pictures would be worth a thousand words..

For any damage repair you need to look and think about what caused the failure and that is a determination as to how or if to fix it.

For instance, is the crack due to impact damage, or is it from fatigue and flexing? Is the crack next to a stringer or transom or bulkhead?.. Just slapping some glass and epoxy over it isn't necessarily going to fix the problem. If you don't know why it cracked and where and how, you may just make a mess of things trying to fix it.

Sorry not to be of much help, but you really haven't given enough information to get the help you are looking for.

 

I agree with yellowjacket. You need to assess why it cracked in the first place. It's no good masking a potential fult somewhere in the hull. We will need more information on where the crack is and what it looks like to give an answere.

 

i will try pics

 

the boat was hid knocked off poppets

 

i have ground out inside replaced stringer ply that was bad the crack i believe can be seen although it holds water before i start glassing i want to make sure that by covering it and grinding from outside will be correct i laid up 3 layers of glass in the very forward compartment so far with marine epoxy and 1700 45/45

 

I'm not sure what the thickness of your hull is, but you're on the right track. If you have about 1/2 to 2/3's of the laminate thickness reinforced/replaced, where the damage was on the inside, you can now safely grind from the outside, fill the area with the remaining fabric thickness, then fair it off, for paint. The biax was a good choice, more bang for the buck.

 

thanks par the hull is about 3/4 inch or more its 1974 egg harbor glad im on th rihgt track is it okay if the crack is still there just layered between 4 layers each side

 

Ideally, you should grind out the crack or at least 80% of it. The real key is two fold: feathering out the surrounding areas, for bonding surface to the hull shell (both sides) and replacing the damaged laminate with more material (fabric). 3/4's of an inch is a lot of material to build up, which will need to be done in stages, because of the exothermic reaction.

4 layers of 1700 biax, hand laid is about an 1/8", maybe slightly less if you're good. This is 68 ounces of material in one shot and about as much as you'll want to do in one session. Let this "kick off", so it's no longer tacky, then apply another 4 layers, staggering the overlaps of each layer, as you go. You need something like 4 sessions of the quad 1700 layup on the inside and 2 on the other. This will get you your 3/4". Naturally, you'll want to be just shy on the outside, so you have something to fill and fair. You can decrease this amount by leaving some of the damaged laminate in place, but no more then a short 1/4" (grind the hull until it's only a 1/4" thick in the damaged area, feathering out from there all around) to be safe.

If too much of the damaged laminate remains, it can propagate stress risers (more cracks) through the new stuff. Epoxy's better adhesion, strength and bonding qualities will help, which is why you can leave some still there, but ideally, it should all be removed. I'm assuming the epoxy will wetout the broken bits of remaining laminate and do a good enough job of holding things, with the addition of biax reinforcement. Simply put, error on the side of too much reinforcement, as you'll not have issue with this, but you could if you error the other way.

 

i think i uderstand its a tough place to grind on the outside because it is in the center line which eventually becomes the keel when im done grinding outside sould i still lay up big to small also the boat is on poppets and blocks do you think the forward block could be changing the shape of the hull im concerned that mayb when im done glassing inside and the pressure is off the block the hull may change i have pics of damage on the outside i will load them later thanx again

 

here is hull damage there are some gouges but i think you can tell which one is the crack it is large for about a foot but carries up the hull maybe 2 feet but smaller

 

thanks par

 

Yep, you need to really move the edges of that crack "back" until you see good, clean mat. Once you've ground back to good laminate, then the edges need to be feathered back further, several inches in all directions so you have a place for the new to transition to the old. Sometimes, you'll have to crawl around under a boat, welcome to boat repair. I don't think this crack will affect hull shape, though it might move a bit if stands are rearranged. If it's fair on the outside, it doesn't matter much, assuming you have sufficiently bonded replacement fabrics in the repair area.

 

thanks par i did some grinding outside already i will be up there on sunday so i will get some pics of what ive gotten to

 

Attached is the usual sequence of events filling and repairing a crack. The one side is ground back, with a generous tapered feathered edge (all around). This depression is filled with fabric and resin. then ground smooth or faired to the surrounding surfaces. Then the the same thing is done on the other side. The long, tapered and feather edged "ramps" serve to offer bonding surface and a transition from the new, replacement reinforcements, to the old, formerly broken ones.