[Chain]

QUOTE (GT40's @ 13 May 2011, 23:12) <{POST_SNAPBACK}>Just another note on aplying copper tape on PVA paint ,in hindsight and for future Ill try some sticky glue before putting down the tape as its more likely to come off or wrinkle due to wheather changes on a phorus PVA than on latex paint.

That's interesting. I'll put a thin coat of PVA around the slot before applying the tape then. I'm already going to use a bit of mixed down PVA (probably 1:3) to keep the tipex-roller white lines in place. I'll get that done tomorrow, maybe start on some of the rocks. No taping until Monday at the earliest, depending on the paint.

Polyurethane has been suggested as an all-over coat. I'm loathe to do any more than is needed, and I don't want to keep spending money either, so a Wait And See approach is best. I do have to have it up and running by middle of next week, I promised my son it would be running by the Thursday....

 

[John Cahill]

re: " I guess the only way to prove it is to take the SAME car and do it once with a magnet and once without. "

I think it would be pretty easy to estimate how much metal is in the paint...I mean, how gritty is it when you rub it between your fingers. Simply ratio the amount of iron grit in the painted area slightly larger than the size of a magnet to the amount of iron in the same length of rail. Multiply that times the amount of magnetic pull. This doesn't need to be analytical...just imagine it...and you'll quickly realize how little attraction there is (although as has been stated, obviously there is SOME pull).

If I follow this thread correctly, we're talking magnetic paint covered by water base something (latex?) covered by PVA then urethane?? Surely I've missed something. May I suggest simply acrylic latex, flat, two coats with a roller. And urethane tires IMHO. That will give you good grip. If you want magnetic attraction, go with the aforementioned steel braids. Also, the advice to let this offgas for a week or so before doing anything else...very good advice!

John

 

[Chain]

At the moment it's simply MDF, a coat of water based primer, 2 coats of solvent based magnetic paint, then another coat of water based primer over that. The PVA coat isn't going to happen as apparently that's not the best, and urethane is unlikely as well. As long as the solvent paint can cure under a coat of water based paint (I forgot to mention it's primer earlier) then I think I'm good.

 

[AAWSCC]

Hope I didn't offend MR F. That was not the intention.
I was just trying to give my opinion.

As for the suggestion of using steel braid, yes I agree that would give you a lot better magnet effect, but I think, like me, it's a cost thing. Copper tape is so much cheaper.

 

[John Cahill]

hi, Chain
ok, so water-based primer/magnetic solvent-based/water-based primer...as long as that solvent-based middle layer has time to off-gas I think you're golden (although that's a big if...getting through the latex will be tough, and a heat gun could be a consideration since you have a deadline *grin*). Fwiw...assuming the "water based" primer is actually acrylic latex...which is fairly typical...then the primer is exactly the same composition as the topcoat itself . With acrylic latex the only reason it's called a primer is because the tinting is useful as an undercoat or it has special properties like an anti-mold additive (and of course this isn't true of all paints..in many cases it literally is a primer which aids adhesion between the base material and topcoat).

Also, I just wanted to add to my earlier comment. Personally I have acrylic latex, copper tape and urethane tires. I really like that combination and would recommend it to you. My mention of using steel braid was only if you are sure you want some downforce. Wood tracks are surprisingly smooth...and IMO work just fine without downforce. But obviously that's in the eye of the beholder.

Good luck with your paint and overall project...hopefully it will reward you with many years of grins and memories with your son!

John

 

[MrFlippant]

Not even a hint of offense taken, so no worries. I find this all interesting and thought provoking, and that's a good thing.

 

[sacesta]

I put down 3 coats of Rustoleum magnetic primer on my track followed by 2 coats of flat latex. If there is any magnetic downforce it is probably negligible. I can't feel the downforce holding the car just above the track but I can feel slight downforce if I hold the car's magnet alone just above the track. The magnetic primer does give the track a bit of texture that seems very realistic to me. Cars handle well with silicone Slot-It S2s or Super Tires.

 

[Chain]

QUOTE (sacesta @ 14 May 2011, 20:30) <{POST_SNAPBACK}>I put down 3 coats of Rustoleum magnetic primer on my track followed by 2 coats of flat latex. If there is any magnetic downforce it is probably negligible. I can't feel the downforce holding the car just above the track but I can feel slight downforce if I hold the car's magnet alone just above the track. The magnetic primer does give the track a bit of texture that seems very realistic to me. Cars handle well with silicone Slot-It S2s or Super Tires.

I can't feel any pull by lifting the car from the track, but just sliding the magnet along itself, it sticks quickly to the areas with the magnetic paint. So I guess it's going to do something. I've "speckled" the track so it has quite a bit of texure now

 

[Chain]

QUOTE (John Cahill @ 14 May 2011, 10:07) <{POST_SNAPBACK}>hi, Chain
ok, so water-based primer/magnetic solvent-based/water-based primer...as long as that solvent-based middle layer has time to off-gas I think you're golden (although that's a big if...getting through the latex will be tough, and a heat gun could be a consideration since you have a deadline *grin*). Fwiw...assuming the "water based" primer is actually acrylic latex...which is fairly typical...then the primer is exactly the same composition as the topcoat itself . With acrylic latex the only reason it's called a primer is because the tinting is useful as an undercoat or it has special properties like an anti-mold additive (and of course this isn't true of all paints..in many cases it literally is a primer which aids adhesion between the base material and topcoat).

Also, I just wanted to add to my earlier comment. Personally I have acrylic latex, copper tape and urethane tires. I really like that combination and would recommend it to you. My mention of using steel braid was only if you are sure you want some downforce. Wood tracks are surprisingly smooth...and IMO work just fine without downforce. But obviously that's in the eye of the beholder.

Good luck with your paint and overall project...hopefully it will reward you with many years of grins and memories with your son!

John

Thanks for the detailed post John

I considered magnabraid initially, but the cost was too high. I like the idea of magnetic paint distributing the down pull across the width of the track rather than just the rails.

I don't have a heatgun, but I'll be out tomorrow with a hairdryer trying to speed things up

 

[Chain]

Not had the time for the heating the paint yet, been doing FRocks all day, but the paint is definitly curing

Very noticeable in some areas, not in others, but I have little doubt now that given enough time, all will be well. I'm going to try putting the tape down tomorrow, but may wait until Tuesday.

 

[John Cahill]

I'm glad to hear things are curing...excellent news. One obvious caution...if you lay the copper tape down while it's still curing (and shrinking slightly), you'll end up with wrinkling tape later or perhaps tape that pulls up in places. Hate to be a wet blanket, but a little more patience may pay off in spades in the long run *smile* Meanwhile...if it's worth it to you...on the other side of this argument is that copper tape is very forgiving for making splices later on. You can always cut the tight areas, relocate the tape pieces closer to the slot again and bridge the gap with a fresh new short piece...leave an inch or more on either side of the splice.

Look at all the rich modeling experience you're getting from this project ! *grin*

best wishes
John

 

[Chain]

LOL yeah. Trying to be optimistic, I've been working on it solidly the last 5 days yet it's still nowhere near. Maybe the tape can wait until Tuesday.... I have a few spare metres of tape with conductive sealant so I can splice any areas easily enough.

I said earlier everything is curing, but then later I took a big chunk of top coat off when the staple gun caught it. Hairdryer tomorrow I think.

 

[1 32 slotter]

Hairdryer is a good idea. I used the mag paint and toped it with latex and had one heck of a time getting it to dry. I ended up getting a propane heater (the jet type) and blasted the shop to about 100 degrees F. That did the trick. How warm is the room you are working in? Track needs to be warm to help the tape stick too.

Good luck: Joel

 

[Chain]

Good to know I'm not the only one who has struggled with this!

The track is in the shed. It can get very hot in there in the summer, far too hot to stay in the shed, so that should do it. Just started getting sunny again today, so if things hold up it should be fine

Matt

 

[Chain]

I'm delighted to say the paint is now pretty much 100% there

There are still one or two areas where it's not completely cured, but these are improving daily. I have no doubt it's all going to be fine now. Taken a long time, but an important lesson learnt and hopefully of use to other people in the future - if you're putting on magnetic paint, give it a week or so to cure properly before putting on the top coat!

Thanks to everyone for the help, suggestions and support