Need educated, on DIY poly resin fairing putty

[Steve Quate]

Hello
I am pretty new to this forum, I mainly search and read what I need to know. I at a crossroad and kind of confused. I’m building a catamaran style fishing platform to get me to some of fishing spots down here on Texas coast till I get my down payment I want to buy another boat mine was stolen down there last year along with 95% of all my fishing gear. Insurance still hasn’t paid me. Another story
Here is what I’ve got done so far. I have both what I’m calling pontoons built & glassed. I used 3 layers of 6% woven and 1- layer of 1708 biaxial fiberglass. I use poly resin(fiberglass Warehouse DCPD ortho blend polyester resin) had no problems with it, I laid each layer coated it let it dry next day repeated process till finished laying 1708, the. Riled on a generous amount of resin fir last final costing, it dried perfectly, rock hard no sticky or tacky whatsoever.
I’m wanting to make my own poly resin fairing putty, just too expensive to buy already mixed. I have the 1st pontoon already faired, used Total Boats fairing putty great stuff but dang expensive. And I hv a lot to fair or smooth out. I hv 6 gallons of resin sitting around. I don’t understand after researching for couple days reading I hv to add wax to the mixture. WHAT? Why add wax if I don’t have to, to me this just complicates things when I don’t really need to. I know gel cost requires it, but if I’m just using poly resin, MEK, glass micro balloons if needed silica. I laid 4 layer of glass w/o wax and each layer dried perfectly, why woujd I add wax to it now and hv to clean it off. I mean if poly resin with MEK, only adding glass micro balloons, not changing the basic recipe that much just glass micro balloons, it should still dry rock hard and it sticky or tacky whatsoever, RIGHT? I know I’m a little slow in my 60’s but old school is old school correct. Why woujd I add wax to the recipe? Did I miss something here, surely I’m not that ignorant.

Maybe I’ll ask this also will be question #2.
After I get the fairing putty down and sanded the way I want, do I really need to apply 1-2 layers of primer or. Am I jump straight to 2- coats of gel coat. Or shoujd I apply 1-2 layers maybe help cover up any mistakes or marks maybe. I never been this far into glassing before.
Please don’t cut me up really bad!! Learning just like all of you, everyone learns the same stuff just different speed. Thanks in advance to anyone that helps me GOD bless everyone stay safe.
thanks again

Will be posting more before gel coating

 

[Blueknarr]

It will be much easier to achieve a fair surface with manufactured compound than diy compound. Home made compound varies from batch to batch both in density and hardness. These differences will sand down at different rates.

 

[fallguy]

I cannot offer much help on poly fairing compounds.

Resins do not dry; they cure through chemical reaction.

Gelcoat will NOT cure with oxygen present. The reason you can buy no wax gc is for use in mold where oxygen is not in the mold after a new layer of something is applied. You need wax for your plans.

The laminating resin you used is different and designed to cure with mekp and in the presence of oxygen.

I don't know how poly fairing compounds work enough to formulate one. I had one 5 gallon bucket here that required mekp; so probably nothing in it that oxygen prevents cure.

You cannot change the chemistry of these compounds.

You can buy products with different chemistries.

listen for words from wiser men than me, good luck on the laguna madre!

 

[kapnD]

Some resins come with wax already added, hopefully you didn’t use something like that in your lamination.
Fairing putty may be expensive, but IMO, well worth the cost in ease of sanding.
You may find that your unwaxed products clog up sandpaper very quickly.

 

[wet feet]

Don't add wax.It is used to provide a smooth and non-tacky surface if you use the gelcoat for flowcoating and works well as such.It isn't so good if you need to apply a second or third coat as all wax has to be removed to allow adhesion.Fallguy is quite wrong when he states that gelcoat will not cure with oxygen present,but right in that it cures by chemical reaction.There will be a sticky surface but that can be removed with acetone and sanded/polished to a high gloss.You need a satisfactory surface before you apply gelcoat or paint,whichever you choose will magnify any undulations that are present once polished.If you have the resin and would like to experiment then I would suggest trying a mix with microballoons or Fillite.Do some testing and keep a record of the mixture used so that when a satisfactory result is found,you can replicate the formula.Its going to be a lot of hard work whichever way you go but the end result can be worth it.If somebody comes along and suggests spraying the final result with gelcoat be very aware that everything in the area will become very sticky,so it is best to build a plastic tent over the boat and use the best extraction you can organise.Consider also that if your neighbour has a car parked downwind of the extractor,it too will get a fine film of sticky gelcoat and you will not be poplular-so factor it in when picking a day or use a brush and accept the subsequent work.

 

[Tops]

The Total Boat poly fairing compound has some warnings for use below the waterline involving barrier coat.
I am not sure if polyester gelcoat over a barrier coat or any other primer/paint is a good idea.
Have you considered paint instead of gelcoat?
Hopefully you can get advice from your vendor or someone in the know replies here.

 

[wet feet]

I hope the OP hasn't applied anything over his glass that won't be compatible with polyester gelcoat.A skin of gelcoat over the laminate is the way most boats are created,but normally from the outside and working inwards.The paint goes on the outside as the last process in the sequence and to do otherwise would be to invite trouble.

 

[fallguy]

@wet feet

Not going to argue with anyone, I've stated my qualifications are non-existent, but this is the basis for my statements and a general knowledge only about gc.

https://support.jamestowndistributo...ence-between-gelcoat-with-wax-and-without-wax

 

[wet feet]

That doesn't explain how or why gelcoat repairs are carried out and frankly makes me doubt the experience of the guy that wrote it.The formulation one uses when laminating a hull is different to the formulation used for coating,one has 2% wax added and one doesn't.Adding wax or using a flowcoating formulation when another coat is needed necessitates abrading the surface to establish a substrate that will accept a bond.It is possible to cover a wet gelcoat with cling film to deprive the surface of contact with air and it won't be sticky.

 

[ondarvr]

Your laminating resin cured tack free because DCPD isn't as air inhibited as other types of resin, it will become tack free on its own in a few days.

Mixing fairing compound yourself can work, but you'll need to do a bit of testing to get the blend correct.

How much time will this boat spend in the water? That blend of resin isn't really considered a marine resin for extended immersion. And making fairing compound with it could be a problem if you leave it in the water.

As for primer, no primer is needed under the gel coat, but gel coat is difficult to sand, so you need to get the surface good before applying gel coat.

And as mentioned, it's far easier to use primer and paint than gel coat.

 

[philSweet]

So if you are going to proceed, you want a decent sized batch of general purpose "mother sauce" that you can fiddle around with. Take a 5 gallon pail. Add 2 gallons of resin, then 2 gallons of bubbles. Mix until bubbles are incorporated. Use a drill press with paddle mixer and make an air-tight lid that can slide up the paddle. I used to push the paddle through the pail lid and then use a glove to seal the shaft the rest of the way. Then take two gallons of fulminated silica. Yes it all fits in a 5 gallon pail. Add the silica in a two or three lots to get it incorporated. Then mix (on slowest speed) for several hours or overnight. That's the basic mother sauce.

For adding MEKP, remember there is only two gallons of resin in there. You figure your MEKP on resin content. For large batches mixed up in the field, Add MEKP to some resin and mix for a few seconds, then add to the pail and mix well with big, low speed, drill and paddle. Don't whip air into the mix. Float a little resin on top of the putty if need be. You really need a second person to mix while you apply the stuff. Then you can make adjustments with any additional additives you might need.

 

[gonzo]

That sounds about right.

 

[Steve Quate]

It will be much easier to achieve a fair surface with manufactured compound than diy compound. Home made compound varies from batch to batch both in density and hardness. These differences will sand down at different rates.

Thanks fir your reply I appreciate it will order some I’m looking at thanks a bunch