How smooth should hull be when tabbing in stringers

[N over my head]

I have spots where there is old woven roving next to where my new stringers are going to be. I have ground down to good solid glass, but there are still spots that are not good and smooth due to the fabric of the old roving. I’m using 1708 and polyester resin. I don’t want to just keep grinding on the roving spots and making my hull too thin in places. Does this need to be smooth where I’m tabbing my stringers in or am I going to be able to just go over these areas with my 1708 and get a good bond with out getting the areas perfectly flat? I very well could be overthinking all of this. I do that sometimes.

 

[zool]

I have spots where there is old woven roving next to where my new stringers are going to be. I have ground down to good solid glass, but there are still spots that are not good and smooth due to the fabric of the old roving. I’m using 1708 and polyester resin. I don’t want to just keep grinding on the roving spots and making my hull too thin in places. Does this need to be smooth where I’m tabbing my stringers in or am I going to be able to just go over these areas with my 1708 and get a good bond with out getting the areas perfectly flat? I very well could be overthinking all of this. I do that sometimes.

as long as its clean and contaminate free, its fine. The rough spots will probably give a better bond than the smooth.....

 

[tpenfield]

There may be some unevenness, but as long as it has a fresh grind over it, you should be fine, as @zool indicated.

I think some folks grind the hull more than needed.

 

[Scott Danforth]

If you can call 24 grit ground fiberglass smooth

Post a picture. Usually when you think you have ground enough, there is more to do. Need to make sure your down to good glass and you are out about 8 to 10 inches past the stringers

 

[N over my head]

I’ve only sanded a small spot. Wanted to make sure I was on the right track before proceeding.

 

[Scott Danforth]

Now stand back 15 feet and take another pic. We can zoom in, we can't zoom out

 

[N over my head]

Here’s a better view after I did a bit more grinding.

 

[Scott Danforth]

you have a lot more grinding to do

 

[N over my head]

you have a lot more grinding to do

Do you think you could elaborate a bit?

 

[Scott Danforth]

all the light spots are delamination of the original tabing. you have to remove that

 

[N over my head]

all the light spots are delamination of the original tabing. you have to remove that

It was never tabbed in per say. The stringers were just shot over with a chopper gun. At just half effort I might add.

 

[todhunter]

It looks about how mine did...I think you're good. In line with what Scott's saying, if while grinding you see a spot that looks light start to appear, chase it for a little bit, as it's probably a bubble / delamination from the original layup. On my boat, I could tell if I got all the way through the roving and into the outer areas of CSM, and I wouldn't go any further.

The hull doesn't have to be dead smooth. The 1708 can conform easily to dips and undulations in the hull, but if you're just trying to lay it over a lightly scuffed up 24 oz woven roving, you're going to get all kinds of tiny air pockets, or you're going to have to use a ton of resin to fill it with.

 

[Davetowz]

The stringers don't have to be fair. The concern is more about a rough cut for mechanical bond. Whatever you bond then in with will eat the roughness. Then coving before glass will smooth what needs smoothed. Just make sure clean before each step, and if using epoxy, don;t forget amine blush cleanup.

 

[N over my head]

Thanks for the replies everyone. I’m about to go outside and fit one of my stringers. I hope you all have a good day and God bless.

 

[Grub54891]

I ground down to good glass. It took off a layer of the original glass, so I put that back in before fabricating the new stringers. I used one of those flapper sanding discs for a angle grinder for the final smoothing before glass.