Longboard or wet sanding ?

[jerome]

Might sound like a strange question but İ will have to choose either one.

İ made myself a longboard which İ have been using to make my hull as fair as possible, but İ am using dry sanding paper that İ buy by the meter here in Turkey. Water proof sanding paper, however, only comes in sheets İ guess about the size of an A4. So İ will not be able to glue them on my longboard for water sanding the hull before primer. Therefore İ am left with 2 alternatives:
1-keep using the longboard and sand the hull with dry sanding paper. That means also having epoxi dust all over the place (actually its been the case for a long time, so no real issue there)
2-switch to water sanding for an optimal pre-primer surface preparation , which also implies in my case dropping off the longboard and using the smaller sandind pads (A4 length)

Your choice ?

[bendoo]

I'ld longboard until you were sick of it and save the wet sanding for the post primer and in between finish coats part of it.....
take some time here....you'll be looking at the results for a long time, and no one else will see the flaws like you will.
Cheers!
bd

[jerome]

That sounds about right. Longboard and maybe one wet sanding before first coat of primer. Then wet sanding all the way baby !

By the way, it is really good to hear from you Ben. You have been far away from our forum but İ guess you have better stuff to do now that your boat is in the water !

[Kevin]

I recommend you sand pre-primer to 220. And then sand primmer to 320 or 400 before paint. More than that and you are being obsessive. Post paint I sanded bottom with 600 and then 800 and might have done 1500 (can't remember due to blocking that from my memory probably).

Look for a consistent pattern in the finish. When it's all about the same "dullness", then you know the larger scratches from the prior grit are all gone and it's time to go up a grit. Trust your finger tips too, they will tell you the difference. A micro fiber towel will also snag on any bumps you have left behind.

When wet sanding I found that narrower strips of the fine grit papers worked better for me. If it's to big of a piece of paper (width or length) it would just bind up and suck down to the surface. Spray adhesive should hold the paper to your long board and still allow you to pull it off. When you get super fine you can go to a smaller block because the grit is so fine it won't effect you fairness anymore. Just don't focus on any one area to long and use long consistent strokes.

Sand finish coat as much as you want. I'm working up the nerve to sand and then buff my topsides. They did not get sanded after painting. The coatings are so thin I worry about going through them. But they are also so tough that I probably shouldn't worry. Any one have experience with aqua-buff?

Kevin.

[jerome]

Guys,

this is the post İ was writing yesterday when the server crashed. Your input is greatly appreciated.

So İ pretty much thought İ had a fair hull ........that is until İ hit it with the longboard.... Only worked the starboard side but was surprised to discover how "unfair" it is.
İ have two large spots which will need fairing for sure. İ just did not see them before laminating the hull. Dont ask me why. Both of those spots are at frame level so İ probably pulled the hull panel in slightly too much . But they are not my main concern.

The real issue is i have zillions of dull and shiny spots all over. As you all know, dull spots means they were sanded by the longboard, shiny spot were untouched and are therefore lower.
İ am not sure what İ should do. If İ keep sanding, İ might get into the cloth of the high spots. İ could probably sand some more but i certainly dont want to find out İ have gone through the fiber cloth. No more patches !
Cant picture either trying to fair all of these low spots with fairing putty and squeegee. It would be crazy ! Maybe İ should roll on a thicker coat of epoxi and filler, sand , eventually reapply a new coat until everything is smooth...?
The weird thing is that İ carefully looked at the hull panel before laminating, and after laminating and it looked pretty good. After sanding the first side, İ went back to the port side to look it over again. İt looks damn fair to me but İ am sure now that as soon as İ hit it with the longboard, those nasty dull and shiny spots will be all over again !

What do you guys think İ should do ?

The attached picture was taken with my phone and is low resoltution but İ guess it will be enough for you guys to understand.

25042011186.jpg

[jray]

Jerome what I did at the point your at, was to float fairing material (micro balloons) over the hull again. I used a flexible concrete trowel that was about 16" long. It allowed me to just work the low spots, then long board again. Then fill and sand, fill and sand. Hopefully someone else has better advice that dose not include more longboard time.

[jerome]

Thanks Jon for the answer. Makes me feel a little less lonely in my fairing misery.

Since this is the first boat İ am building, and therefore have no previous experience or references, İ kind of expected almost no fairing after laminating because my hull looked pretty fair before. Man was İ wrong !!!!
Would a thick coat of resin and fairing filler applied with a roll work ? Cant believe İ have to go back to squeegee or other longer trowel and apply the thick stuff....???! Plus İ end up using tons of resin and fairing filler to get enough putty to the right consistency.....

Another concern of mine is that for strength purposes İ wanted most fairing to be underneath the fiber, and not on top of the fiber. İ mean, wont having filler directly underneath the paint make the hull kind of soft, weak and very prone to dents ? İs that something to worry about ?

[jray]

I used the long trowel to try keeping the amount used just where needed and no where else. I did most all of the fairing as you did, under the glass and epoxy. I don't think you will have strength issues chasing small stuff. Sanding flow coats of epoxy is tougher then sanding fairing material. This is my first build also so don't count on my advice being the best or only way. I even long boarded after the first few coats of primer!

[jerome]

Went back to the drawing board and looked back at all blogs İ usually refer to. Found a very interesting description in ClownFish's blog. That is pretty much was Jon was suggesting. More plaster of disaster :

"After glassing, go over the hull with a batten and fair any obvious hollows and bumps with your West system stuff. The next step is to screed the entire hull in a thin coat of West System fairing compound. I used a plasterers trowel for that. The next step is to get out the long board with 40 grit on it. Because we had relatively flat panels and frames spaced about Four feet apart at the back, I made a Twelve foot (2.4m) Two person longboard for the bottom and chines. You only need a Three foot flexible one for the sides.

Get yourself a can of spray paint in a suitably visible colour and liberally spatter dots of it over your hull. Apply the long board....After about half an hour the remaining paint will show you the low spots. If they are relatively small and shallow, fill them with "builders bog" (quick setting polyester) stop for lunch, apply a little more spray paint indicator and continue sanding with the long board. When you think you have it fair, apply your first coat of undercoat, then apply the long board, spray paint, filler and 80 grit to that. Repeat the whole process for Two weeks till you are sanding the final undercoat with 320 grit and everything is as smooth as it can get, or you just get too tired to care. Then apply topcoat."

Any other good suggestion ? İ am going back home soon to break another sweat with that longboard

[admin]

Great find, Jerome. Those last 2 sentences are a little daunting...that puts in the water circa May 26th, 2028.

[Kevin]

First. I'm sorry to report that the long board never lies. You could have been flexing the panels before they were glassed. Now that you have glassed them they are stiffer and holding up to the pressure while sanding. Don't over sand at this point. Use your board as a tool to find those low spots at this point.

I'd give the long trowel to avoid putting on tons of filler where you don't need it method a try. I put on lots of filler and sanded most of it off again trying to fill all of my low spots. Again, don't over sand. For me the worst part was roughing up the low spots so the epoxy would bond. It was like finger nails on a chalk board for me. I used a pencil to circle the low spot and then roughed it up with 60 grit sand paper across the flow instead of with it. Recommend a tint in your fairing compound so you can tell the difference between the layers. You'll see the progression to smaller voids that way and identify over/under applied areas faster. The spray paint idea isn't a bad one either if you have an old can lying around.

Your finish will hold up fine over time, trust the epoxy to do it's thing and you are going to use a good primer so you should be in good shape.

Keep at it my friend. You will get there. Kevin.

It only get's better as you knock out those low spots.

[jerome]

Another good piece of advice but the highs and lows on my hull are actually really, really shallow. Honestly speaking, although i can clearly see them after İ have used the longboard, in most case İ can barely feel them with my hand. İf İ had big depressions, that is what i would do. İndeed İ almost used this technique when fairing the bare hull .
Latest news is that İ bought myself a 16 inch long trowel last night and applied a really thin, wet, smooth layer of fairing filler all over the starboard side. İt was really easy to apply and the results seem very promising. İt looks like most of my problems are solved but İ will only know for sure after longboarding again tonight. At least, İ am much more confident then before !
İ believe the main issue is that my initial float coat was probably too "floaty", too thin. İ did use some fairing but certainly not enough, just to make the resin barely cloudy, because İ wanted to roll it and did not think a thick mixture was necessary. İ was induced to think so after reading the swift solo tutorial.
Will keep you guys updated on progress.

[Ron Bowman]

I tried using spray paint as a guide coat a couple of times but did not use it after giving it a try. The idea is to spray a thin layer or splatter of paint which is then sanded off with a long board leaving the low spots visible. The part that I didn't like about that method was having to sand the paint. It seemed like if I sanded too early, it gummed up my paper. And if I left it to dry completely, it was harder to sand than the surrounding fairing putty. Seemed like I was making a little more work for myself by spraying on paint that had to be removed before applying more filler. Then after identifying the low spots that way, you have to mark the low spots somehow (I just used a pencil to circle the lows), you have to go back and sand the paint out of the low spots before applying more filler. Instead of using paint, I decided to try a product from 3M called Dry Guide Coat which is kind of expensive but lasts a long time. I only needed one pack of the stuff to finish my boat. It's a black powder that almost looks like copy machine toner. It comes with a hand applicator. So you rub the applicator with the black powder in it on the faired surface instead of using spray paint. It turns the surface dark gray which you then sand off. You still have to mark the low spots and then come back and rough them up before applying more filler but I liked that product as a way to avoid having to sand off the paint spatters as part of the paint/guide coat method. The powder guide coat just seemed like a little less work than paint guide coat.

Ron

[bendoo]

I found that shutting off all the lights and shining a flashlight along the hull showed me lots of lows and highs I didn't see otherwise...the shadows were very revealing. Then I would circle them w/ a pencil and turn the lights back on, add filler, and wake up the next day to more sanding...YAHOO!!
And like Kevin said.....the longboard will tell you alot as well.
bd

[jerome]

That 3m stuff sounds great. Just watched a tutorial on Youtube but could not find it anywhere in Turkey web stores. Worst Marine does not carry the product either...İ will stick to my cheap can of spray paint.
Quick update on the fairing misery :
-sanded the hul again last night after the last application with the 16" trowel. İ was amazed at what that thin coverage did for my hull panel. All shiny low spots are pretty much gone ! İ was so happy. The longboard was "singing" along and the whole panel looked SOOOOo much better that before. So İ faired some more and removed all excesses than aplied what İ believe will be the last coat to fill in some deeper scratches. That final coat was wet and shinny. As İ applied it on the somehow faired hull, the trowel would just slide along and very little fairing was actually left on the hull. And because it was not a thick heavy coat, the resin still had some self leveling capabilities.
So a few minutes after İ applied it, the whole panel was glossy and shinny . Never looked so good.
İ turned on the heater and let the boat rest. İ will see what it looks like tonight but İ do believe İ might have finished that coating step. İ might carefully sand it once more with the longboard just to make sure there is no excess resin/putty on the hull, then İ will water sand it for primer prep.
Thanks you all for all the good advices !
Learning how to build a boat is really an extremely rewarding process. Might just consider a career change here....

[jerome]

Ok guys,

after a very long weekend dedicated to dry sanding and fairing the hull, İ guess İ am close to switching to water sanding with 220 than apply my first coat of primer ! İ am really happy as fairing and sanding this hull was pretty labor intensive job. Sides were relatively easy as İ could reach all the way to chine, but the hull bottom was a whole other story !
No idea how you guys did it but İ had no other option but to climb on top of the hull and sand in a very discomfortable kneeled down position...! I would regularly go out of breath , mainly because of the respirator, and just sweat like if İ was running a marathon. İ dont know if İ am getting old or out of shape but İ swear İ was physically exhausted after one of those sanding sessions. Two 2 hours a day sessions (morning and late afternoon) is all İ could handle. İ would just eat and rest in between sessions...

Question: the only thing İ am left with are minor scratches and small pin holes. Do İ have to get rid of them with epoxy fairing putty or can İ already switch to primer ? Will the primer fill some minor holes or serves only as a base for the paint to stick to ? İ am getting sick of 410 !

[jray]

Jerome, most primer does a good job of filling and hiding small scratches. Some are better than others, the primer I used took several coats instead of one to get the results I was looking for. Drop the manufacture a note and ask.

[Kevin]

Jerome,
I would plan on multiple coats of primer and keep the first one or 2 coats thin so they flow into those holes instead of going over them. I had no issue going over pin holes and got a great finish using E2000 2-part primer. I think you are using something similar if I recall correctly. And using different colors or tinting the coats with pigment (which you can find at just about any paint or HD type place) really helps when you are sanding out the primer. Then you know when you hit that bottom layer and don't want to sand any more.

Oh, and I climbed up on my boat to sand the bottom. There was no other good way to do it. I used a kneeling pad on top of corrugated cardboard for the knees. Sanding is the worst and best part. Lots of work of work doing this...

DSC_0679.JPG

and you see no real results until you paint. When you see this...

DSC_0769.JPG

Keep at it. Kevin.

[jerome]

Woah ! What an amazing paint job. Truly inspiring !

Ok thank all of you guys for the advice. It is now 8 pm on this side of the world. I am going down to my garage for another sanding session. Maybe water sanding....At least i will use 220 for use ...Bought some very nice and expensive 3m sanding paper. They come in a very light shade of grey...Never clog.
I guess priming time is coming soon.