DIY fairing boards

whats your preferred fairing compound for glass jeff.

 

Depends on the substrate & job. If I was finishing some mdf plug with a seal of glass to build tooling it would generally be Q cells with a dash of colloidal silica and similar for any polyester job with the paste pre mixed in buckets(power stirred with the mixer through a hole in a board to keep the dust in) and catalyzed later . Sub waterline generally better to go epoxy and same required over any epoxy substrate would use Qcells, or the purple brown phenolic micro balloons again with a little colloidal silica added- this helps the filler come off the broad knife a bit smoother and neater. On epoxy we'd sometimes use a final screed of West microlight mix as it goes on sweet and smooth but use the cheaper extenders for bulking out. Often now I'll just get the pre blended International 833 or the equivalent Jotun or other brand- often called "frog bog" as it's green
Edge tools such as planes work very well on extended resin, they do need a touch up on the oilstone now & then but a lot more satisfying than grinding away on the torture board all day- where they really come into great use is where you might need to "top up" some small areas to height- the action of the plane actually just cuts the high spots off whereas sanding can give a halo effect around the top up. Some jobs with heaps of energetic(young & cheap) labour can be achieved with a bulk overfill then apply the boards and labour wholesale... I'm a bit older and slower so like to sneak up on the surface fairness, usually three careful screeds will get there. The use of a fairing/torture board will always be required for the best result but I use a combination of board, plane, 8" planetary action rupes sander, 6" rupes random orbital, 7" festo rotary sander. Guide coat always handy as without easy to get snowblind as to what & where the surface is at. Another trick on flattish surfaces which are actually harder than curvy ones is to use bog battens to define edges and mid panel fair lines, I think in auto trades now they call them "splines" but basically smooth battens that get loaded with filler, applied to surface then taken off after setting- (they need release agent). I use 25mm 12mm x 3mm aluminium channel as cheap and sits pretty fair.
So choice dependent on substrate and on budget also, I'm getting to old to enjoy the dust in both mixing and sanding so dont plan on doing to much in future but who knows as work and business very variable currently..
Jeff.

 

The guide coat to spray on...how do you not interfere with epoxy bonds of follow on layers of epoxy compounds?

 

excellent. thanks.

 

great post

 

Agree Brendan, seems Sailhand uses a very similar process, I've evolved mine to minimise the effort and material use. One of the best tools for small areas is a planetary action sander, I've had the Rupes model for I think about 27 years, if its a panel say 600 x 900 it will be sorted in no time if you float the machine right. I've personally never used the machine style that Sailhand also posted though I can see that they'd be pretty handy if on an open panel with no chance of an inside corner, I saw a hydraulic model used years ago but the guy just hired it and had little idea despite good advice. Be very careful of vibrating machinery as they will do damage to your hands and fingers. One issue I have is after 40 years my "trigger/rude" finger to right hand has a tendon pain... lots of spraying, jockying screw guns and MIG welder triggers has taken toll with vibrating machines not helpful either.
Jeff.

 

I typically mark around any depressions/holes/scratches that appear after sanding with guide coat with a pencil. Once marked everywhere I scuff out the guidecoat with sandpaper by hand for small areas and a random orbital for larger areas being careful not to remove my pencil marks. Just basically remove the guidecoat if using a spray paint misted on. If using the powdered type guide coat a quick wipe with acetone and then a light key sand only if the bog is older than a few hours. It also depends on size of the hole. If its a tiny scratch glazing putty is quick and easy if its a large area then a good keysand for secondary bonding is essential. The guide coat should only be the lightest of mists and therefore easily removed. You will be surprised how much it stands out against snow white bog, really easy to see.

 

This fairing device is very interesting. Can you tell me more? Did you make it your self?

 

I purchased the first one and made the rest. They're not available any more. Cheers

 

thank you for your response
Is the electrical part an angle grinder or da polisher? I want to make one to fair a fibre glass structure


Hennie

 

You can use anything you think will run it. I find1500 watt motor plus low gearing works great. The one pictured is a festool stirrer but I only used it once. I find the traditional grinder style drive more comfortable and easier to control. Usually a sander polisher. Don't push down on it, in fact lift and support it or you'll burn your motor out in minutes.

 

Thanks. I was thinking of a polisher with variable speed. the sanding attachment: spring steel, fibreglass set up in a cross?

 

The helicopter, as it is affectionately known, is all fiberglass. I believe they used a desert bowl with a dead flat base and a wide flat flange around the rim to mold the top part. They then cut 4 triangles out of that molded piece to form the cross shape. The bottom cross is a tiny bit concave but basically a flat piece of glass also with the four triangles cut out to form the cross. The two pieces are then connected together with what appears to be Eva foam blocks. The Eva is a bit firmer than say crocs shoes Eva but still flexible to absorb shock and allow for flex. A really easy simple alternative, but not as good, is corecell or divynicell foam, cut into a 300mm diameter circle and Velcro attached both sides. You can then attach it to any Velcro pad that fits your sander polisher. I like a flexible interface spongy pad for this as it allows the foam to conform to the surface. Obviously the foam needs to be flat or even a tiny bit convex/concave so that the outer edges touch. If not you will "dish" out your fairing compound and create really expensive dust. For large flat surfaces use 15 to 20mm mdf for your circle, only 200mm though. The mdf needs a more solid mounting though so i use the backing plate off an old sander polisher pad and screw it on. It goes without saying that your mdf disc and torture board must be dead flat. Also the Velcro must be as thin as possible to keep the papper flat. The most important thing to remember when using this is to never stop moving. I use a basic figure eight movement and gradually move up and down and along the hull with these figure eight pattern movements. A really good fairing batten and guide coat are the important keys here. I constantly check my progress with the batten as I work along. These days I think I do more batten checking so my poor shoulders can cop a rest but if you aren't into expensive pointless exercise then less is more. I don't chase the guide coat. I see plenty of beginners just mindlessly sand until the guide coat is gone.""WRONG""¡¡¡!!!¡¡!. THE IDEA IS TO FORM A FAIR CURVE. the guide coat is to highlight the dips. If you don't have patches of guide coat everywhere when your done your doing it wrong. Imagine a rail line running through a mountain range. They cut away the mountain tops and bridge over the valleys. They don't dig down until they are level with the lowest valley. You should be way more interested in what your fairing batten says, not how many guide coat spots you can see. Go back and fill the guide spot holes afterwards. I generally fill them "flush" and then top coat over again. A good block plane with the blade set really low is great for patches if just sanding them you might dish out the bog around the patches and create problems for yourself, again guide coat guide coat guide coat. Then it's torture board time. If you've done it right and your using polyester in your guide coat holes for quick drying you should be able to run down the side of a 40ft hull in a day and be ready for high build. Then it all starts again. Food dye in your hole filling bog is handy, just a smidge, to see where the patches are and again with the guide coat. That little spray pack of mat black paint lightly misted over the job will save you thousands in materials and your poor shoulders and lungs. First thing that goes on after high build is guide coat again then the process starts again with finer grits and torture boards only. Torture board is the fastest and most accurate once your nearly there. The first part is where you want your block plane and fairing batten followed by my helicopter and figure eights. Then patch holes and torture board entire surface with same figure eights on torture board, this is really quick now maybe 30 to 45 mins for 40 ft cat one side of one hull. It should be really fair before you hit the torture board so if you've guide coated again, as you should, it is really fast. As soon as the bulk of the guide coat is gone move on, don't stand there torture boarding away like a mad man and digging holes that you will have to fill. Too often people get totally lost when fairing and are unsure if it's right or should they keep sanding and then sand holes into there hard work and then sand more holes trying to fix the ones they just made. It's like watching my neighbours crazy dog go round and round chasing it's tail. The road map is the guide coat, without it you are stumbling around in the jungle in the dark like a lost puppy.

 

Thanks for that explanation. I can picture it now.