Crack Back

I think 52 would be a good quick fix. You can still grind the area over and epoxy it later.

 

You almost had it...just left a bracket off the front...  [ 



That looks to be a little bit deeper than a stress fracture.  :-?
I'd grind it out and reglass the area.

 

You might want to drill out the ends to ensure that the crack will not continue to grow once glassed over.

 

Take a couple more pics of that area from top left and top right
looking back at the transom and post them. I'd like to see how
far the crack extends along the float chamber.
And one from the outside so I can check the exterior gelcoat.

To repair the crack you'll have to remove the interior gelcoat at least
4 to 6 inches each side of the crack to create a strong bond to
the existing structures. Don't use just mat, add some woven
fiberglass layers to the repair. Fiberglass mat doesn't make for
a strong repair. Alternating woven with mat produces a stronger
more durable patch. Not a hard job, just messy.

 

brett is rt. ---but use bi-axial cloth and epoxy---start w/ small patches going progressively larger---as suggested

 

That is bigger than I thought. you will want to cover your hands and arms before grinding or you will be itchy.

Hey guys, I've heard that mat has a wax on it to bind it together and epoxy does not have the chemical reaction to remove this wax and will not bind well. Can anybody verify this or is there two types of mat?

Also GG, do you know if there might be water inside the chamber and might have waterlogged the foam?

 

Those cracks are known as hard point fractures.
Fiberglass is very flexible except at sharp bends.
Any time a flexible fiberglass panel meets a hard point (sharp bend),
the possibility of a fracture occurring goes up greatly.
The transom is laid up as a single fiberglass skin
with the rest of the hull. The floatation compartments
and benches are added afterwards and are not built as well
as the rest of the hull. So any hull flex transfers unevenly to
the components glassed in later. Your fractures appear to
be caused by the weight of the outboard shaking the transom
which has caused the separation fractures you are seeing.
The transom is peeling away from the benches.
I can tell this as there are no cracks on the outside of the transom,
and the symmetric fractures to the tops of both benches.
Is the bottom of the transom and hull properly
supported by the bunks on your trailer? If not, after making
the repair, those fractures will occur again.

 

Hey guys, I've heard that mat has a wax on it to bind it together and epoxy does not have the chemical reaction to remove this wax and will not bind well. Can anybody verify this or is there two types of mat?


Chopped Strand Mat is held together by a chemical binder that is broken down by styrene allowing it to "wet out". Epoxy does not contain styrene, so it is unable to break down the binder holding the mat together.

but use bi-axial cloth and epoxy

I would not use epoxy for this job. If you use polyester resin, you can easily use gelcoat to finish off the repair and match it to the rest of the boat. Polyester is also cheaper and you won't have to worry about future issues with bonding a polyester to an epoxy.

 

you just need enough glass to make it level with the existing surface . that would be one of those guesstemant deals. the most important part would be to grind the area wide enough to spread out the bond area and feather the grinded area so you get some depth into the existing fibers.

I would do it all at once so you dont have to grind the new glass for the next layer.

also, you don't want more resin than fibers or vice-versa. not to dry or too wet.

 

mat mat mat mat matmat mat mat mat mat mat mat mat mat mat mat mat mat mat mat
                      biax biax biax biax biax biax biax biax biax biax biax biax
           matmat mat mat mat mat mat mat mat mat mat mat mat mat mat mat
                         biax biax biax biax biax biax biax biax biax biax biax
                mat mat mat mat mat mat mat mat mat mat mat mat mat mat
                                                         crack


layup make sense?

Cut fiberglass to fit
mix polyester resin with mekp per instructions on container
apply resin with 2 inch cheap bristle brush

apply resin, set mat, apply resin, set biax,
apply resin, set mat, apply resin, set biax,
apply resin, set mat, work out all air bubbles,
let harden, sand irregularities smooth.

Throw 2 inch brush away...

 

You could probably get a better resin/glass ratio if you only do one or two layers at a time. If you lay up subsequent layers while the previous one is still tacky you can avoid have to sand in between. Also, if you use a knitted biaxial material like XM1708, or a stitchmat (woven roving with mat stitched on) you could avoid having to lay mat between layers. They will also build thickness in less layers. The downside to those products is that they have a larger profile and might require more fairing than a biaxial cloth like Brett is talking about. If it were me, I would go with the XM1708, but Brett's method is a good option as well. Keep in mind that regardless of the glass you use, you want to use the least amount of resin possible without leaving any dry spots in the glass.

If the crack is only in the gelcoat, this in no big deal. If the crack goes through into the glass, then you have a structural issue. If the latter is the case make sure you wrap the glass up onto the transom to reinforce the area.