USC Garage SMC Filler and Gel Coat

[Batteryman]

Has anyone ever used this filler and top coated it with Gelcoat or know if they are compatible? I'm repairing the fiberglass bottom of my Blaster using some polyester resin. (it's what I had and that's what the factory service manual says to use) and am finding some sort of fairing compound would be really nice. I'm also using some cloth and Cabosil. Sorry if this is a dumb question but I am very new at fiberglass repair and reading/ learning what I can.

I talked with Total Boat and they said since my ski does not stay in the water I could use their Polyester fairing compound that is designed to be used above the water line but its $40.

 

[WFO Speedracer]

The whole myth about gelcoat not sticking to polyester and epoxy is bogus , yes you won't get a chemical bond , but if you do it right you will get a mechanical bond which means you need to leave the surface rough enough to create that bond, I like to use 80 grit as my final sanding before shooting gelcoat.

I have used that exact filler before and gelcoated it with no issues.j

 

[Batteryman]

The whole myth about gelcoat not sticking to polyester and epoxy is bogus , yes you won't get a chemical bond , but if you do it right you will get a mechanical bond which means you need to leave the surface rough enough to create that bond, I like to use 80 grit as my final sanding before shooting gelcoat.

I have used that exact filler before and gelcoated it with no issues.j

I was hoping you would have an idea!. Thank you Ill give it a go! I would think a mechanical bond would be sufficient. Im sanding the entire thing down with 80 before shooting the gel coat.

I have been watching Fish bump TV on youtube and learned a lot there, he has some really good videos.

 

[WFO Speedracer]

The best tip I can give you on shooting gelcoat is to use either Smoothie additive or mix the last few coats with Duratec clear, either will cut sanding time in at least half, patch aid is also a product I use sometimes. If you are just spraying gelcoat make sure it has the wax additive in the gelcoat or it will not surface harden , if using patch-aid or Duratec clear you don't have those issues , the smoothie additive also has to be used with gelcoat that contains the wax additive.-

Gelcoat will not harden in the Prescence of air , when it is sprayed into a mold it's not an issue ,the wax additive in the gelcoat floats to the top and seals it off from the atmosphere , you can do the same thing by spraying a light coat of PVA over the gelcoat repair, both the wax additive , the PVA and the Smoothie are fairly cheap , the Duratec clear not so much .

 

[Batteryman]

Thanks for the tips! I have not heard of the Smoothie additive, the Duratec seems popular though. yeah at $50 Duratec is not cheap..

This is a race boat so I was going for a bit of an orange peel on the bottom and planned on sanding the sides smooth. I was impressed with JaveStack's results using just styrene.

Barbie Car Blaster

New member, gotten a lot of great info from this forum already, much appreciated to have a source of knowledge. My father got a one owner square nose superjet 650 in great running condition for $300, and he is cleaning it up with a new black and white livery… this development made me jealous. We...

www.x-h2o.com

I was thinking of getting this gun with the 2.5mm spray tip.

https://www.amazon.com/dp/B0D6RFFSPJ/?coliid=I14M0ZGWFWE34G&colid=3B7PRC8GFFMPZ&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it

 

[WFO Speedracer]

2.5 tip should work as with any gun and tip you will have to thin it till it sprays regardless of what the gelcoat mfg reccomends .

Just keep in mind not to mix more than you can shoot , after you add catalyst you only have about 10-15 minutes to empty the gun and clean the gun out or you end up with a really big mess.

 

[Batteryman]

I found that out using it mixed on a board last summer on an 90 degree day. boy does that stuff get hard really quick! Its been in the low 50s here for a high so im going to wait till we get a 70 degree day

 

[Batteryman]

Would you have any recommendations on how to build up the center portions a hair that all the gel coat is removed from? I am trying to remember what they are called, its not a skeg. Over the last 31 years previous owners have ground the tops of them down a bit. I tried putting a 1 inch wide woven mat over the top but when I would get one side stuck down the other would keep lifting. A wider piece and then sand the outsides more I guess or build it up with some filler..

 

[WFO Speedracer]

Take a look at this thread , hopefully it will help you some the chines were ground down pretty well on that one.

650sx rebuild and restoration.

This on a customer's 650SX , chines are beat to hell and back as well as the flat section of the bottom deck . engine, electrical driveshaft, waterbox are removed from the skj. I flipped it upside down on my trailer and started the repairs, I flooded the flat part of the ski and sanded it back...

www.x-h2o.com

 

[Batteryman]

Thanks for the help and documenting repairs for us learning! I will pick up a little bit more resin and give that a go. Do you think using a healthy amount of Cabosil would be ok or best to pick up something like this?


I used the taping trick you showed in your flipping thread when filling some large gel coat chips and it works really well.

 

[WFO Speedracer]

I would only use cabosil for heavy duty filling , if you have something like a chunk missing or a gouge then use cabosil , but cabosil is a total PITA to sand , I use phenolic micro- balloons filler , specifically the SM fairing compound from US composites , it is the best I have found thus far , if it needs to be harder than that you can always mix in some cabosil to make it stronger and more dense.

Micro -ballons is very versatile filler , it can not only be made into a putty like bondo but it can also be mixed up thing and painted on with a chip brush , use the masking tape trick to make it lay down where you want it and to define the edges of the filler.