Resin Cracks

[76SeaRay]

In the very bottom of my hull (keel), there are two places about 2 to 3 feet long (engine bay and amidships) where it appears that the factory dumped excess resin. It appears that with hull flex or just age the resin has cracked. I wasn't able to grind it out yet as my belt sander burned up due to glass dust and I have to go get another one. So, do you think that the cracks go all the way through or just through where they dumped the excess resin? Is this common in boats? I can't see any cracks underneath the boat on the outside although the boat is on the trailer so not easy to see. I do plan to grind it down and cover with 2 or 3 layers of 1708 just in case.

 

[froggy1150]

Yea...Grind it out and reglass. Dont let the excess pool like the factory did. If it didnt crack all the way thru it could at some point. Its not allowed to flex right like that.
Side note.... what i did to help my power tools was to wrap all the intake vents with resperator mask paper. I would kinda peel ot a bit to adjust airflow

 

[GSPLures]

The burgundy grinders from harbor freight work good for that. They are cheap so you are not tearing up expensive tools. Just dont go with the cheaper black grinder from there those dont last at all

 

[76SeaRay]

They have 3 different brands of belt sander, Warrior, Bauer, and Chicago Electric... It looks like you are referring to the Chicago Electric one which is on clearance... My old one was the Chicago Electric and it lasted quite a while.

 

[Scott Danforth]

I would use a 4.5" angle grinder with 24 grit and have the hose from the shop vac ready

 

[GSPLures]

They have 3 different brands of belt sander, Warrior, Bauer, and Chicago Electric... It looks like you are referring to the Chicago Electric one which is on clearance... My old one was the Chicago Electric and it lasted quite a while.

I was talking about the grinder, i missed the part about you using a belt sander (my bad). Not sure about their sanders, I used a grinder for mine.

 

[76SeaRay]

Oh, ok.. I think the combination of the angle grinder and the belt sander should do it. Heading to Harbor Freight to pick up a new belt sander in a few minutes. The belt sander will help get the surrounding area prepped for the layers of 1708.

 

[76SeaRay]

Started grinding on the cracks. Switched to my 1/2 inch belt sander cause I was concerned about being too aggressive with the angle grinder. I had to go pretty deep, maybe 3/8 to 1/2 inch. You can kind of see that with the screwdriver in the picture. Anyway, crawled under the trailer and I could not see any cracks in the gelcoat. Pushing on it at the point where I ground it feels pretty solid. So I don't think the cracks went into the hull from the pooled resin. This is going to take some time being careful not to burn through the hull.

 

[kcassells]

Basically its just excess resin that has cured at a high temp then the temps make a fracture like you are seeing. Underneath will be fine just grind till your happy then throw some glass over it if you want. Factory boat guys are slobs. In my case I cut grinds into it and chiseled it out then sanded smooth.
I've seen that crap so high that it actually prohibited flow to the bilge.

 

[76SeaRay]

Pulling the boat out of the shop and into my driveway today to do massive grinding. I already have too much fiberglass dust in my shop.

 

[Lectro88]

Pulling the boat out of the shop and into my driveway today to do massive grinding. I already have too much fiberglass dust in my shop.

Just so you don't feel so bad.
My 1969 mako had some of that around the bilge area, however mine did not go that deep and my epoxy wasn't that deep either. as it wasn't puddled against stringers.
Mine (I think)is what is called minor spider web cracking.
I simply sanded with belt sander and aggressive orbital sander and along with filling the corner voids where the hull meet the transom with a hairy mesh in holes under air bubble pockets.

as kcassells says and he is correct. Factory boat guys are slobs.​

(at the back corner riser (I will call it)and along the bottom where the hull turns up to the transom, The back "U" if you will.. both ways. bottom to top and front to back.
I laid 3-5 layers 24 oz. old school woven and I extended that about 18" forward as far as I had the stringers cut away at the time for transom replacement. I don't have or have not purchased any 1708.
Best I can tell, the hull right there "was" about or almost 1/4'.. I figure its now 5/8"- 1/2" it seems to really for sure be solid now.
This cracking you see is exactly why I use milled fiber and or chopped strands in my PB. and I know that may be getting slightly off topic.
But its along the same lines. From what I have been told by some resign dealers and 2 of these blend and make their own epoxies and resigns.(1 in Calif & 1 in Fla.)
They tell me extra epoxy is no good without glass. It almost always will crack at stress or flex points without glass. And PB to my findings is even more brittle without some help when you start adding fumed silica or thickening agents. I cut up my scrap ravelings real fine and mix that sometimes to thicken, and that makes things really tough.
What you're doing is looking good. You get some glass laid down with some 'goo' lol. and I think you will feel much better.

 

[76SeaRay]

Thanks, sounds like I should use epoxy in this area instead of polyester for layering the glass once I get the pooled stuff out.... The light spots where I have ground it down look like the top of the woven that was used in the hull lay up... Guess I should also go with woven instead of 1708?

 

[kcassells]

Thanks, sounds like I should use epoxy in this area instead of polyester for layering the glass once I get the pooled stuff out.... The light spots where I have ground it down look like the top of the woven that was used in the hull lay up... Guess I should also go with woven instead of 1708?

Get to a clean base, use your poly and stick with 1708. Non-issue. :}

 

[Lectro88]

Epoxy is stronger since you are relying on a mechanical bond now.
You would probably be ok with poly too. hopefully others will chime in.
I don't consider what you have as a "real failure". IMO its more cosmetic as the glass probably didn't fail. you just had cracks in "Excess pooled Epoxy"
:Edit.
I said pooled epoxy.. I should have said resign. If its original its most likely poly99% thats a slip of the keyboard tongue.{sorry}
ANYTHING you add at this point is kinda a bonus.
So far as 1708 I don't know the stuff personally and this is only what I remember from reading.
If it has the mat that depends on the styrene to dissolve or melt. I think thats the right words, anyway the poly is "best" for that, I know others have used it with epoxy but its said its wasteful and uses a lot of epoxy and full benefit is not achieved.
I was always pleased with woven, flip a coin its your choice. if you don't like it you can always re-do or add more to it.

keep posting it may help someone else.
I sure do really appreciate everything thing I have learned from this site.

 

[Lectro88]

Get to a clean base, use your poly and stick with 1708. Non-issue. :}

kcassells your post came in just as I was finishing typing.​

I didn't mean to contradict you or your post.
I actually hoped others would comment and you reconfirmed poly is good enough. kinda what I said too.
I have mostly done epoxy thus far. Only tested with poly 1-2 times
Still getting my sea legs with poly.

 

[todhunter]

Poly will be fine. And 1708 does have mat stitched to one side - but since it's stitched it doesn't need the styrene binder to hold it together, so epoxy will wet it out fine. Plain CSM does have the styrene binder and will not become as pliable when wet with epoxy, as it does when wet with poly.

 

[kcassells]

kcassells your post came in just as I was finishing typing.​

I didn't mean to contradict you or your post.
I actually hoped others would comment and you reconfirmed poly is good enough. kinda what I said too.
I have mostly done epoxy thus far. Only tested with poly 1-2 times
Still getting my sea legs with poly.

Nothing wrong with your comments, all good. I favor EEppoooxxxyy as my glue of choice too. I recommend finishing with what you start with. Poly is fine.

 

[76SeaRay]

Well, 3 1/2 hours later the pooled resin with cracks is ground out in the area where the 60 gallon fuel tank and the galley walk area is located. Still have a little in the bow and the area under the engine (very thick there) so estimate 3/4 done. I got it relatively smooth in the very bottom of the keel and didn't burn through anywhere. I also scuffed the hull around the keel up to the stringers as I plan to lay glass across the entire bottom between the stringers. Should I put a fillet of peanut butter in the very bottom to smooth and round it for the glass?

 

[Lectro88]

Man, that looks good. !
Looks like you are ready for glass.
I can't see where where you need PB.
Unless you were going layup on the sides of the stringers.
and the existing glass looks perfect.(no cracks) just calling for some company...
And I know you will feel better when you add a little resign and glass.
This area will be tough.

 

[kcassells]

Wow.. Looks great. I mean clean as glass. Looks like you could just go right over it with glass and be done.
PB is a good precautionary prior to glassing. Only you can see the nicks and grind outs.