Infusion Plan

Groper, you must have had a bad piece. Fram on his large catamaran build had no problem with bare foam on the entire build.

… Having said that, I will always use a mold from now on as I think fairing is the biggest waste of time, adds weight, is weaker than a solid infusion and I intend to use double cut perf'd in the future.

 

Ok thanks I'll have to try a test.

 

Before I screw up more than I already have, can I get an opinion …

I am just about done fairing and I notice the flange is kind of small, in some areas the fillet really does't leave too much flat area which kind of ruins my idea of bolting a toe rail with lip all around. I might be able to do it but the backing plate would be pretty small for sure.

I was thinking to laminate a piece of coosa to the edge all the way around and then glassing that to the fairing compound, is that going to hold or is it just going to pop off over time? I would then screw the rub rail to the coosa.

Here is an image to show what I mean …

 

Well the bond line will only be as strong as the fairing compound...not good. I would grind through the fairing compound just where the mating faces meet, and just deep enough to expose the laminate beneath. Bond the finished coosa strip and leave it at that, no need to wrap glass onto your already faired deck or hull as all it's doing is holding a rub rail...

If you make the coosa strip taller so it sits proud above the deck line, it will give you a toe rail aswell...

If you want the coosa covered in glass, glass it before you bond it on...

 

Hi Jorge - If you use a tough adhesive like a urethane or acrylic (plexus) it will be oK. But an epoxy or VE would slowly crack. Regarding infusing timber. I have infused MDF, pressure treated pine and various plywoods. Woods job is to transport water along its pores and it transports resin really well too. So I've had some early jobs absorb huge amounts of resin. So preseal end grains with a light resin coat before you infuse. MDF makes a great tooling board if you infuse it solid. If you sand the "skin" off it, its possible to create a solid chunk of mdf/resin very dense great for routing moulds etc. MDF also makes a great resin break or brake but I'm now experimenting with tyvek for that. Peter

 

Ok, glad I asked!! Thanks! That shouldn't be too hard to sand down!

Great tip on the MDF, next build will be all about molds! Going to practice by building a couple of these little guys first, should be less painful learning process!

http://www.soloskiff.com

 

Fairing still in progress!





Today I used a scrap piece of corecell foam with one of those large sanding sheets from the 12 x 18 floor sanders stuck to the bottom. I used this on the with light pressure and 80 grit paper using a random orbital motion and it worked very well, better than the board ... Here is a link to a short vid of that
http://www.youtube.com/watch?v=OnePQsAGMeA

To sand the tunnel I used the foam pad that the floor sander use, it curved to the tunnel nicely and using light pressure I was able to get it pretty good but don't use that pad for very long or on straight surfaces as it will just conform to whatever wave you have, use the rigid foam.

 

Hi Jorge, at this stage of the game when you are fairing it is usual to soot or flash the surface so you can see where you are which I think you have done, but you should work the grit in one direction only. So you work the grit in say the 45deg until you have a nice consistant sandy surface. Then you go down a grit and work on the opposite -45deg until you have another consistent sandy surface etc until done. If you work round and round you will use 10x more energy and time to get the job done! If you already know this sorry but the video looks like you will take a long time. Cheers Peter s

 

Hi Peter,

It def takes energy lol, but works so fast ... the first two coats I did as you said with a long board. I have lost some weight during this stage ))

Do you know what compound this guy is using? Seems to be so much easier to use than my epoxy filler mix!

https://www.youtube.com/watch?v=Se4SuTrznoI

 

What's your mix Jorge? I use 1litre of mixed epoxy, with 125ml cabosil and 2litres micro balloons for my fairing mix. Works for me...

 

I havn't done a lot of fairing (try to avoid that sort of workout! but I'm about to start a plug myself so its on the way!) but it could be an automotive filler. But these shrink if used for plug work. Just send them a note and I'm sure they will tell you. The flexicat tools look cool. Many many years ago I used to make a flexible blade sander for ATL Composites that worked similiar but was run by a hydraulic motor. 24" blade and 12" blade but they stopped selling them. Cheers Peter S

 

Groper - I use the same ingredients but I use more or less resin depending on the stiffness of the mix I want. I mixed 4 gallons of micro balloons with about 3/4 gallons of cabosil and then I use a coffee cup to meter it out into my resin mix as I go. 1 coffe cup for every 5 pumps of resin gives me a thin creamy mix with some slump, I add a bit more if I want no slump but the grey stuff the guy is using in the video link seems to have unlimited working time and zero slump yet sticky as heck ... looks like he scrapes off what he has just applied and then moves to the next section to apply the mix that he just scraped off.

Definitely, I have the wrong tools as well, the long blade of that flex cat does a much better job than my taping knives! they have much less sanding to do using that tool.

Peter - You better make yourself one of those electric sanders or you will be losing weight like me lol!! Try my idea when you get to the last coat, it really works good and the random orbital action eliminates scratches better than directional sanding.

Another funny thing, my finger prints are completely sanded off. I can not travel through the building freely anymore, my finger prints do not register on the scanners that open the door locks, I have to wait for somebody to open the door for me!!

 

Jorge, years ago when I used to do a lot of custom building we used a product called Foam Glass which we called fartrock instead of sandpaper for big fairing jobs, its actually an insulation product. It came in slabs 24"x18"x4" and we cut it into 4 pieces. I is really a miracle product as it cuts like 40grit and leaves scratches like 100grit and as you sand, it wears away exposing new cells so it cuts aggressivley until it gets too thin and breaks. Im having a hard time finding it lately, last time I bought some was quite a few years ago at one of the larger local wholesale building supply places but they don't carry it anymore. Seaman composites in LA used to sell it also.

Steve.

 

Im not sure what the problem is? I can use my mix like the guy in the video... you scrape off the excess and use it further along, keep going until you need to mix up some more...

I use long peices of aluminium angle extrusion as fairing battens. Change the length and wall thickness of the section depending on the curvature your trying to fair. So more flexible, thinner wall for more curves and thick wall for flat parts. Apply the mix liberally using a steel concreting trowel, making sure to apply too much. Then pull the aluminium section across it to leave a fair surface - same as video really. The aluminium angle can be grabbed with your hands easily with your finger tips inside the apex of the angle.
You only need to scuff the result for adhesion, before giving it a second pass as the mix pulls out of the hollows a tad. Impossible to get it perfect in a single pass.

Not as good as the flexicat tool no doubt, but works well and you shouldnt need to sand anything for hours on end if applied carefully with good technique.

After that, you can apply a sprayable fairing compound, sands very easily, and sand it down to within thousands of an inch fairness, then start with your paint system. Ive done the sprayable fairing compound on the topsides, not going any further until im ready to paint the whole boat...

 

I am going to see if I can find that stuff local, sounds great! I am not a good fair man which is cool because I am going the mold route from now on!
… is this it - http://www.foamglas.com

I don't know … his compound seems to last longer than mine. In minutes how long would you say is working life of your mix?

I will pick up one of those angles tomorrow, I am not completely happy with the sides. what is sprayable fairing compound, that sounds like something I want! Is that picture of the sprayable compound, the white part or is that paint?