Lyn #13 - MMB-4 (Fretless)

[robin]

I wish I had a Plan B!!

The polyester coating turned out to be a disaster.


Either a) the wood reacted with the Poly Resin or b) I didn’t stir/mix in the catalyst enough, or c) high humidity or d) the layer of Poly was too thick. Anyway, after pouring the poly resin onto the FB all went well for about 40 minutes, in fact I was quite chuffed as the FB looked like it was behind a sheet of clear glass. But then, the 5mm thick sheet of Poly Resin started to delaminate from the FB. It started with a few air bubbles in the middle, then they started to appear along the whole length of the FB.


I was able to lift a sheet of resin off the FB in one piece. The top surface had cured and gone rock hard but the resin in contact with the wood had not cured and was still tacky.

I will sand back the gunk that’s on the FB tomorrow and see if there is enough resin left in the tin to lay one thin coat on top of what’s left on the FB. That will give me an indication as to whether I can “burn in” another few THIN layers of poly. If I can then I will buy some more resin and keep going. If not I will have to find a plan B.

I am confident that I can save the FB, but it may not look as nice as I had hoped. If I can still get an instrument that plays well then I’ll be more than satisfied.


My biggest regret is that DB went to great lengths to get me this lovely piece of Rosewood and I feel that I need to do it justice. Sorry DB.



Pics of the delaminated piece of Poly resin

[robin]

S-T-R-I-K-E.........2


Tried with the Polyester resin again. This time I made sure that the fingerboard was free of any oils or sweat, checked and double checked the mixing ratio of resin and catalyst, poured a thinner layer, but a fortunately the same result.


After about 40 minutes the bubbles began to appear from the wood again, although the top was hard as nails it had not cured against the FB, and was delaminating like the first try.


Hopefully I've taken operator error out of the equation, so that leaves a) some sort of reaction to the rosewood, b) I'm still trying to pour too thick a layer of resin or c) a dud batch of resin. I could try "painting" on several thin coats but to be honest I think I am done with polyester resin.


I can see 2 options, sand back what's left of the dodgy resin and just go with a naked wood fingerboard or try EPOXY resin!


Having already established that I am pretty stupid and a masochist to boot, no prize for guessing which way I am going.


There is a local boat chandlers near me so I will go down there later today and sus out their epoxy.


Not giving up..........yet

[wokkaboy]

Rob what a bummer, I'd sand back the resin and put thin super glue on. That's what DB uses and I've had great success with it sealing fingerboards.

[dingobass]

O poo!
I have a feeling the Rosewood's natural oils are the problem..

[tonyw]

I would guarantee the rosewood oils are the problem, if you ever seen a rosewood neck someone tried to shoot poly over, thats what happens, i have one in the shed on an old acoustic some kid thought would look cool shiny.

[stan]

it will sand back mate, and i'd stay away from epoxy and poly, i think you will keep getting this result...

build is going well though and its looking great

[robin]

Thanks Woks, DB, Tony and Stan.

You are probably right but you are too late guys. I went straight out and bought some epoxy. I will have one last try with laying a thick coat on the FB and if this doesnt work I will probably try DB's super glue trick.

I'm persevering with the thick coating as I didn't do such a good job with radius block on the FB. It might be ok but I doubt that it will be good enough. I am hoping that with a layer of about 3mm of epoxy and what I learnt from my first attempt I might be able to get a better result.

Hey, building these guitars is stretching my abilities and I'm learning heaps as I go and enjoying the challenge, so it's all good. On the positive side, I've already found 2 ways that polyester doesn't work on rosewood lol.

Cheers guys

[wokkaboy]

Rob may pay to lay on thinner coats but build them up. Maybe it is bubbling because you are applying coats too thick.
To be on the safe side I would see how say a 1mm coat goes and if it doesn't bubble then build it up

[robin]

Yeah Woks, I was thinking that exact same thing.

I asked the guy in the shop about it. He was extremely helpful and had a lot of experience working with epoxy. He said that subsequent coats would have to go on after the epoxy starts to set but before it sets hard. He said a window of anything from 45min to 1.5 hours depending on weather, mix ratio etc. If I got it right the next coat would 'burn in', but if I got it wrong the subsequent coat might not take and if it did I could get witness lines if I sanded through a coat.

He said I should have no trouble with 5mm +/-, he said that he has done 25mm in one pour, no probs. But he had no experience with rosewood. :/

Fingers crossed, I will have a go tomorrow. Not real confident, but I'll never know if I don't try.

[wokkaboy]

fair enough Rob, well best of luck and hope we don't see STRIKE 3 in the heading tomoz !