1980 19-6 rebuild

[Capt.Andy19]

so this might be a stupid question but here it goes... what am i suppossed to accomplish with the grinding? do i just want to get a thin layer or grind down all the old mat that is on there?

[Damage7]

so this might be a stupid question but here it goes... what am i suppossed to accomplish with the grinding? do i just want to get a thin layer or grind down all the old mat that is on there?

Couple of reasons. One is to remove and loose (delaminated glass) and get it down to some solid glass to bond to.

Also smooths down any high or sharp areas so that the new glass can lay nice and flat to minimize air bubbles.

Also it roughs up the area very well for the new resin/glass to secondary bond to.

[Capt.Andy19]

Ok. I've been using 40 grit flap discs. It doesn't seem to be roughing it up. It actually makes it very smooth...?

[love2fish]

depending on what kind of sander/grinder you are using- 40 grit should be more than good.

by "roughing up the surface" we don't mean- get a concrete/grip-tape type of surface, it means to knock the sheen off the existing layer and give your new surface a smooth/fresh layer to lay on and bond with. Grinding the existing layers will do multiple things: clean off any high spots where underlayers may overlap, or glops of resin might have fallen during previous work; "cleans" any top layers of general junk that may have been sitting on the area you are grinding, and lastly- some resins- particularly polyester, needs a "fresh" surface for proper bonding.

not to throw a monkey wrench into the whole thing- but, before you start grinding, try to clean up any oil or grease deposits you may see that are in areas like the bilge or typically found on the lowest points of the hull- depending on how bad they are, you could be spreading and allowing the grease/oil to further seep into your glass. a simple acetone wipe down (depending on severity) can help make quick work of this. Some people even pressure wash their hulls before and then do a simple sand to rough up the existing glass.

[Capt.Andy19]

so ive done a little grinding... i just want to see if you guys can tell me if im doing it right... to much... or not enough... any advice helps. in the pics the darker glass is before grinding and the lighter/white glass is after grinding. the cracks you see are the stringer peeling from the hull. thanks in advanced for the help!

[love2fish]

it looks like you are doing it right, but might need to go a little more. especially on the last picture, and 2nd to last picture- you can see on the HULL side of that section you are grinding, that looks like the top layer of woven glass that they laid down... chances are that layer is compromised, I would grind that off and get down to the hull layer of glass. you have the right idea there on the pictures where you have it grinded down to where you can not see the "check" of the existing woven/black spots"... you want that "chalky white layer, which means- fresh glass you can bond your new material too.

on the areas, stick a flat pry-bar under the edges and see if it lifts up. if so, keep peeling it back. or grind it all the way off.
your new layer is only going to be as strong as the layer you bond it too...and if it failed once,,, chances are, it will fail again.

good work though and keep posting pictures if you are unsure.

[Capt.Andy19]

my concern is on the crack... did i grind to much?

[love2fish]

just work on the bottom area of that crack. clean up that rough glass.

This was from my first 22-2.
the entire inner edge of my port stringer was delaminated. I ended up cutting it out. started grinding only to find a void between the raised section and the hull bottom. I was literally able to take a circular saw, and set the dept the the blade to just cut the raised portion out. then grind everything smooth.
here's a few pics to show you what I mean:

The raised area:


once I started grinding- noticed the "gap" where the 2 layers were separated...


here you can see where everything was ground down to the hull level, this is what you want. and where you can start re-glassing.



you need to clean up that cracked area more- get rid of any class that isn't solid/connected. then go back and add a layer from the stringer down to the hull. add a fillet, and glass over that again. each time using different widths of glass so they are binding multiple layers and not just the exact same footprint each time.

the glass on your stringer looks ok- just continue to grind until you get the "sheen" and dirt off- , the hull part- I'd grind that whole top layer ( you can see the 3-4" section of glass they used as the bonding layer) off and bond the stringers freshly to the hull.

[Capt.Andy19]

what do you think about cutting the stringers out and putting in composite 1.5-2" stringers? what material would you use? im thinking this might be easier???

[love2fish]

lots of people do that. but if that is your only crack. its a pretty easy fix. how do the rest of your stringers look?

comes down to cost/time/piece of mind/ability. 

[Capt.Andy19]

Is this what I need to get it looking like?

[RickK]

You're getting close   
You want all the "print" of the cloth gone so you have a nice smooth place for cloth to stick. You can see the "shine" on the lip at the bottom of the stringer - scruff that up too.
When you start to glass them together you'll want to be mixing up some peanut butter consistency resin with cabosil, and maybe some chopped glass, and hopefully lift the edge of the lip and stuff some of the resin under to combine the bottom of the lip with the hull under it - so if possible see if you can get the grinding disk under the lip in a few places.
To attach the stringer to the piece of stringer liner that is now "the hull bottom" you'll need to lay in a fillet of thickened resin along the bottom of the stringer where the lip starts and lay in a 4" wide strip of 1708 cloth (2" up and 2" down) and then immediately lay in an 8" strip over the 4". Make sure you put the CSM part of the 1708 down.
You may decide to scruff up all the stringers and lay a strip over the entire hull and stringer to tie it all together. That will tie everything together but remember that the cloth you are laying in, as was said earlier, can stick to the old but oif the old isn't really stuck well, then....

[Damage7]

what do you think about cutting the stringers out and putting in composite 1.5-2" stringers? what material would you use? im thinking this might be easier???

That is what I chose to do but if I could go back i would have just saved the old ones! As the others said if it's just the crack on the bottom that's fine. You can just grind the part away that attaches it to the hull and then re tab it with glass to the hull.

Looks like you are getting better at the grinding, but yes as rickk said you need to get all the printed woven fabric off. When you're done it should basically be all white and you want be able to feel any fabric pattern if you rub your hand over it.

I know it's scary grinding down that much because it feels like you'll bust through the hull but there is quite a bit of glass there to work with. Go check out my build and you might get an idea.

[Capt.Andy19]

im thinking of now doing my rebuild following the bateau 22 flatback. so stopping what im doing and doing the transom. anybody agree or disagree in that procedure or how they did it?

[RickK]

If I remember correctly they gutted that FB (like I did on my 170) and started fresh.  That is a BIG decision to make and if you think the grinding is bad now, wait until you need to grind the entire inside of the hull (been there, done that).
What shape is the transom in? Are you planning on making the transom full? Adding a bracket or a lift/jack plate? They cut out the entire transom - you can do that but if your transom skin is not bowed it will be easier to stay with the existing and build upon it.