Grinding and sanding...how far is far enough?

[Daniel1947]

I am slowly working my way down the hull grinding and sanding. I am wondering how far is far enough? I also know that if you see the ground or daylight, you have gone too far. And knock on rotten wood, I haven't gone that far yet.

I believe that the area in red is probably far enough.



Opinions are welcomed on the following: Area in green.



I am almost 100% sure that all this mat showing in blue area needs to be ground away, which is what I have been doing up to today.


What I have been assuming is that if it is shiny, area in yellow, it needs to be sanded down to a dull finish.



I am getting there and as always I appreciate the input and information.

Dan

 

[friderday]

Welcome....always want to get down past that "shiny" stuff. Think ruff-n-scuff. That "mat" you refer to is actually woven. Again, I just ground any shiny away, being careful to get to good, sturdy glass with NO air pockets. The woven I've seen in original layups especially, are prone to containing air pockets or resin voids which offer little or no strength at all. Grind out any of those voids, but in the pics I see, not looking too bad. You will notice them as you grind as the glass just flakes away. Get rid of those, but IMHO, don't think you need to be too aggressive. What are you planning where you are grinding? A fresh layer of glass? Faring material? Hope this is a start. The real experts will be along soon. Pics of the whole boat give us a better perspective and something to drool over.Lisa

 

[friderday]

Oh, and seeing daylight doesn't always mean you've gone too far and ground thru the hull...It could just mean there is a thin or no layer of gelcoat on the outside and you can actually see daylight....unless of course you've ground thru the hull, can see daylight, and can work on your trailer rollers from inside the boat. In this case, you've ground too far.

 

[GT1000000]

Yes Sir, Miss Lisa has you pointed in the right directions...
Basically you need to think of the glass like, well, glass...if it is all shiny and smooth, nothing will stick to it...if it is dull and rough...you get the picture...
Lisa is also 100% correct about seeing daylight...if the gel coat or paint finish on the outside is removed, the fiberglass will become translucent and it may appear that you have gone too far...
Another very good point she makes is to get rid of any suspect areas of poorly laid glass...in some cases that may require grinding a small section almost all the way through at the same time creating a dished out area to be filled back in a few pieces of CSM and 1708 to bring those areas back to level.

 

[Rickmerrill]

Want to see too far loos like just see my boo-boos starting around post 50 when I come clean. Not that big a deal but... Is there a reason you're grinding all the way up the gunnels? Up past where your tabbing and deck glass go is far enough unless you have a reason. Once you see it starting to flex when you push with your hand you're getting pretty thin, flex with your thumb and gelcoat is the next thing you'll see! I don't know of a better way to tell. Red looks good, green close, if it's thick enough you can grind it flat or maybe you could use a less aggressive disk and do touch ups?, blue I don't know, yellow just a scuff. No expert just opinion.

 

[Georgesalmon]

Light will come through white gelcoat to. We usued to paint black gelcoat on the inside because when owners saw sunlight they thought the glass was thin. It was over 1/2" thick.

 

[Daniel1947]

Thanks Friderday, Gus, Rick and George for the input. I guess I shouldn't have made an attempt at being a comedian, however I do know the difference between thin and actually having holes in the hull, LOL. :lol:

What I was attempting to evaluate was what should I actually be looking for when grinding. I know that I can use a 36 or 40 grit flap disc on my 4-1/2" grinder and make one easy pass and remove some of the resin, but how far - how much - is enough. I know that if the last application at the factory utilized "wax," then the wax has to be removed to ensure a good bond between the old and the new. I also have a good professional Black & Decker 7" high speed grinder, and Gus I am sure you know that with a 24 grit paint buster disc, it will remove material very quickly. I have been using the 7" with a 50 grit to make light easy passes to just knock down the rough stuff, mainly in the larger flatter areas that are within easy reach. Then using the 4-1/2" with flap discs to get into the tight areas. I want to remove the least amount that is necessary, but also want to ensure that only a good sub-surface remains.

After almost 4 years here on the forum, and reading and re-reading threads, seeing mistakes, seeing people giving up, and seeing people completing great boats, I have learned that all the pictures and videos can't answer all the questions that usually raise their ugly heads while actually getting dusty and itchy.

Rick, as to the reason I am going all the way up the gunnels, is to remove some of the spray foam that has remained. And, "NO" I don't need to see what "holes" look like. :facepalm: I also plan on completely sanding/grinding down the interior of the hull; I am not sure if I am going to lay in a layer of glass (like you did Gus on the Bassassin) or not. There was not a lot of room under the deck on this boat for flotation foam, so they sprayed probably an inch or two on the inside of the gunnels as well as placed two large foam "blocks" located at the stern.

I had started a thread on the whole project, but I don't seem to have the knack to make it too enticing, so I decided to just post new threads and ask questions as I go along and come to things I am unsure of. Sorry for the lack of photos, etc., but here are 2 links to my other posts.

http://forums.iboats.com/forum/boat...stro-quickfire-18fs-w-150hp-mercury-black-max

http://forums.iboats.com/forum/boat.../7798917-deck-and-stringers-and-transom-oh-my

As always, thanks to everyone for their input. And keep the ideas/info coming.

Dan

 

[Woodonglass]

The problem with starting multiple threads on the same project is, that it gets confusing to the members when you reference things about the project in another thread and then they have to go to those other threads to either look at pics or read comments. That's why the Forum Rules and Guidelines state that you should keep all of your posts concerning a project in ONE thread. I think you make a big mistake when you don't do that. There are lot of posts on the forum each day and it takes time for the members to respond to all of them so patience is required but we do try and will eventually respond to all new posts eventually. When you're in a hurry I KNOW it seems like we're ignoring you, but we're not. Grinding areas that don't need it is a waste of time and material IMHO. Unless the area is weak and needs new glass to reinforce it, I'd spend my time and efforts on areas needing work. As stated, you only need to grind the shiny off so the new resin and glass will have something to "Bite" into. I'd highly recommend 40 grit. It'll go a lot faster. A backup pad and resin coated discs seem to last a bit longer than the flapper discs. At least they did for me. But like I always say, It's your boat and you're free to do as you see fit.

 

[friderday]

Daniel...don't ever lose your sense of humor...esp.on restoration. I hope you know we/I weren't making fun of you or hinting that you weren't fully capable of recognizing the obvious. We're all one big family here and sometimes humor & sarcasm is all we got to keep us from sniffin' the fumes without a mask. I,as most of us,have ground a little too far. I'm my own worse critic, but it sure helps when my buddies make fun of me a bit and remind me I'm human, it's not the end of the world, & it ain't nothing that can't be fixed. With that being said, I used flap wheels and like woody said, just went as far as I needed...no more. Again, just watch for those resin-starved voids, grind them out for sure. I had a very thin, flimsy hull and gunwhales so after ruff n scuff & all air voids ground out, I did put a layer of glass before stringers just to sturdy things up a bit. You keep at it...you'll know when you get there.

 

[Daniel1947]

Lisa, no problem here. I know you all weren't making fun of me, but it did seem like you all missed the little joke about knowing when you have gone too far. I take no offense in any or it. And, BTW, if I ever lose my sense of humor, I understand that I have to relocate to Oklahoma and move in with WOG.

Wood, the reason I stop posting on the original thread, is that there wasn't any following. Like I said earlier, I have been on this forum for almost 4 years. While I have not read, advised or participated in as many threads as many have, I do know that if the thread doesn't grab one's attention, then one won't continue following it. I have experienced that myself. There are threads, such as GT1000000's that I have followed almost from day one, and there are others that I followed for a day or two and lost interest in. When I posted the original, the forum was having all kinds of problems upgrading. I wasn't sure if the lack of following was due to the forum's problems or a lack of interest in my thread. I even went as far as contacting a moderator "Bondo" at your suggestion to see about deleting it. There are enough threads that show pictures of rotten wood, damaged fiberglass, etc. I figured that we didn't need mine. I am not an expert, but I pretty much have a very good idea of what I am doing. I don't plan on continuing with the original thread. If I have a question I plan on asking it, it doesn't need to be connected to an existing thread. I make it a point to make sure the thread "topic" is directly related to the question. You and I have shared some information and I value your input, we had a very nice discussion about my transom. I hope we can continue sharing info and I will continue asking questions. If you are wondering, yeah I took a little offense at your reciting forum rules to me, I am 67 years old, kind of head strong (just like an old Okie I know) but I feel that if there is a problem I would expect a moderator to inform me as such. Now that I have all that off my chest, I look forward to a continued and rewarding relationship with everyone here.

Dan