Epoxy fairing compound over gelcoat

I plan to paint my hull with VC Performance and topsides with Perfection. I have a few scenarios.

Transom is done but needs fairing tying in the epoxy glass into the existing gelcoat. The hull had a good amount of crazing near the bow (alot of flew there from rotted bulkhead). There are also some deep gouges here and there through the gelcoat.

Can I sand all this with 80 grit and tie all these various repair types together? Are there issues with epoxy fairing compound over gelcoat?

If not, do I need a primer such as interprotect 2000 e prior to my standard primer? Anybody know if VC performance can go straight on this.

I asked these questions on the interlux forum but not sure if I will hear back. Also figure they would recommend 6 different products.


Also, I did see the response from 7/11/11 search and not sure if PAR is saying to get the gelcoat off because his is really ragged or because its gelcoat.

 

Gel coat needs to be well sanded and roughtened for you intend to fill over !!If you intend to glass then all the gelcoat needs to be removed down to the bare glass . so you get a good bond and the new sticks well !!. Epoxy filles are not a problem over polyester but you cant or shouldnt use any polyester over epoxy !!.

 

Good News! I was reading myself crazy. Interlux recommended a coat of interprotect prior to the fairing and that created all kinds of doubt.

But yes, all glass work is done and tied into ground original glass (que the angels singing) and now time to pretty it all up!

 

Interlux always wants you to spend more money but not necessary in this.

 

A nice thick coat of high build and then a block sand to make sure all is 110% flat and fair before you final top coats !! Specially where pepairs have been carried out

 

Agreed on the building primer, though a few thin coats to bulk up the film thickness is preferable to a single heavy coat. I'd use an epoxy primer, of which there are several to choose from.

Tunnels is correct about making it absolutely fair, as Perfection or any other LPU type paint will easily show every single surface blemish.

 

A little trick with high build 2 pots is to add a 1/2 cup or Q cells with the first couple of coats and you can build thickness very quickly and its easy to sand then just a thin coat of straight high build over the top and fine wet and dry before the top coats get applied !!

 

I appreciate the adivce guys. I was looking at sanding boards and they have these kits with 6" 9" 16" and 24" for like $49-$69 bucks. Should I go this route?

Then there is 20 yd and 45 yd kits of rolled sandpaper. For a 20' hull should I be thinking 20 or 45? Figure I'll need 4 types if below is correct.

More reading and I come up with:
80 grit for hull prep and fairing
Primer 120 grit between coats with 220 grit prior to VC Performance and 320 grit prior to Perfection. Primer is Epoxy Primekote 404.

Does that sound about right?

Tunnels you mention wetsanding primer, do you typically do that? If so, what grit?

The Q cell trick, 1/2 cup in what volume of primer, just curious. I think thats probably a high school course and I'm elementary.

I only have around 90 SF of area that will be Perfection and 190 SF of VC (with an upside down hull on sawhorses) so I'm down for whatever you guys recommend as well as any others insight.

 

Ok !
After the build and initial sealing teh patch bogging in the worste places and a good heavy long board just to find and get some of the high points and flatten them off !!. Long boards are good for you shoulder muscles because you will discover there are muscles you never knew you had and after a while you wish you didnt have as well !! Long boards need to be flat as light weight as possible with a little flex but also a little firm i always make my own to suit my arms not everu board suits every person . A good coat of primer to seal and try not to actually sand through from this point high build gets a colour change and Q cells added to the pointwhere it not to over loaded !! High build needs to be 2 pot always so thickness doesent mater it all goes hard at the same time !!. Trick is to start sanding before it gets to hard and yet hard enough to sand and not roll up under the paper and tear ot chunks and leave holes . some jobs are a breeze and some just seem to go on forever . 80 grit is about the course-est paper for high build and then 100 to 120 before a good coat of straight high build .
Its at this point i change to using Duratech and after a generous spray job its wet sanding with 220 to start or 320 if its good and flat and not orange peeled Again get to it early and still partly soft . then its up through the grades of paper 320 ,600, 800, and about this point if its possible i switch to using a orbital sander at 1000and add dish washing liquid to the water to help keep the sanding dust held in suspension and all drips off . A nice orbital sand leaves 100% no marks at all any where . i like a small palm sander in each hand and just go for it !! wet sanding keeps the dust at bay and the paper lasts much longer and you get a better milage from it than dri sanding
Dura tech at this stage will take a good buffing and in 99% of cases have a pretty good shine !! this is for making a plug to make a mould over !
If its a finshed job after a repair then 1200 wet and dri sand of your 2 pot painted the surface to knock the dust problem on the head and a sponge pad buff and polish with a little car wax mixed in with the polishing compound
it helps with the final clean off and wipe down .

 

Hey I really appreciate you taking the time to type that all out. That is a big help to have some direction to go with it. I'm going to stick with an epoxy primer, I see duratec recommends not being applied to epoxy fairing compounds with microballoons and I'm pretty sure the stuff I have does.

 

Speaking from personal exsperiances i have used Duratech over almost any kind of surface and never had a problem ever . MY reall test for outside use was my old boat that had a badly mudcracked deck . i sanded and wire brushed the surface and then poured on a coat of durateck and worked it round all over the deck witha squeege to fill the cracks !! then when it was tacky sprayed a generous coat and left it for a day to do what it wanted . 100 grit sand and another generous coat and a 320 wet and dry and behold it was 100 % ok ! so painted 2 coats of light gray 2 part polyurethane industrial paint over the top . That was 6 years ago !! not one sign of the dreaded mud cracking has even shown up any where in all that time !! I have used that same duratech making plugs and finishing repairs over glass , over wood skinned with glass and over the past 15 years have never ever had a problem .
one company pushed there hull plug out in the sun to sand and it went so hard it was almost impossible to sand so havd to recoat and leave inside to sand !!. I always use 100% acetone as a thinner to spray with and to clean up etc etc some people use styrene but i dont like styrene at all for any spray jobs even gelcoat !!.