resin research question

General Discussion
1

okay guys i will post a detailed thread next week but here goes my querrie for now,

im making a wooden skinned board for a friends 30th birthday, all is going well just have to laminate and fit the fin this weekend.

construction is blue dow foam stringer with 1lb eps either side, skinned in 2mm sapele timber with sapele and cork rails.

i got a cheater coat on yesterday to seal the wood and that has sanded down well today.

so 2 questions,

when i lay down the lam coat do i need to let it dry then sand down before hotcoating? (i will be freelapping) or can i go straight over with hotcoat,

and secondly when installing the fin box in the blue dow foam is fast resin research the way to go or should i use 5min epoxy to avoid exotherm?

its all resin research by the way.

cheers guys and as i said detailed build photos next week.

thanks

2

anyone??

please

3

Hey surfingdog,

It makes for a better hotcoat and easier sanding if you sand/grind the laplines before you hotcoat. If the lam has been sitting for more than 24 hours, give it a light sand just to scuff up the layer a bit; the hotcoat will bond better.

If your hole for the finbox (single fin, right?) is tight enough, then fast hardener is ok. If it’s loose, you might want to play it safe. Put a layer or 2 of glass around the box when you sink it as well, makes it nice and tough.

Good luck. Show us some pics when it’s done!

4

brilliant cheers johan,

i will be hotcoating within 24 hrs so ill just sand the lap lines cheers mate.

yep putting a single box in with 2mm all the way round plus i have some rovings for wrapping round it for strength, will this reduce the exotherm worry?

pics r coming, just dont want to post them yet in case my friend comes on here as its a surprise for his birthday.

thanks again

5

throw down a cheater while the lam is still tacky.

then, when that has cured, flip, take down the laps, and glass the other side.

throw down a cheater while that lam is still tacky, too.

6

hi, i would avoid using addative f over wood , it leaves a milky hue in the resin, try a scrap piece of wood first if you are not sure , pete

7

okay im gunna answer one at a time

hope this helps

Quote:

construction is blue dow foam stringer with 1lb eps either side, skinned in 2mm sapele timber with sapele and cork rails.

stringer is obsolete on this construction

Quote:

i got a cheater coat on yesterday to seal the wood and that has sanded down well today.

cheater coat means that you do the next coat while the first coat is still tacky

that means your seal coat was not a cheater coat

Quote:

when i lay down the lam coat do i need to let it dry then sand down before hotcoating? (i will be freelapping) or can i go straight over with hotcoat,

its okay to do this

i let it dry first and get the the weave and laps down

this makes a cleaner sanding

i have done the fill coats as a "cheater " where you do the lam and wait 4 hours then put down the filler coat

and that works as well but i prefer to let the lam cure

Quote:

and secondly when installing the fin box in the blue dow foam is fast resin research the way to go or should i use 5min epoxy to avoid exotherm?

5 min epoxy is the worst dont set plugs in polystyrene with 5 min epoxy

it gets really hot when curing

use slow hardener for your resin research

8

Wax in styrene works better than Additive F. Toulene holds more wax content, but I think its this richness of wax in Additive F that gives it the milky look.

Wax in Styrene, same as you use for polyester…make it ourself:- in fact its a domestic paraffin wax in styrene…no milky filler coats.

Josh

9

hi josh, i think i understood correctly, you use wax in styrene in your epoxy? is that correct ,if so, what is the purpose ,

i used the additive f a couple of times but i did,nt feel it was needed really, pete

10

Hi Josh

Please confirm this

Wax in styrene works better than Additive F

Do you really add this stuff to your epoxy resin on a fill coat?

11

Yes Mark…

Wax in styrene is applied for filler coat resin only, any brand of Epoxy, I’ve found it settles flatter than Additive F in RR and does not go milky. I have found wax unnecessary in the laminate (glassing mix).

In some cases the omission of wax in the filler coat is not a problem, but wax is a safer bet. Play with the amounts a little as its a balance between viscosity reduction and sandability. Its about 2% of the mix content by weight, or a capful in my parlance…

Josh

12

brilliant thanks for the responses guys and helping to clear up confusion on the terminology.

as i said ill post photos at the end of the week once its been given to the birthday boy! i really dont want to risk him seeing it before the big day.

so i sealed the wood first as opposed to a cheater coat, then sanded this down to key in the lam coat. my girlfriend was generous enough to let me do it in her front room as we were down to -5 degrees on sat morn!

i laminated the deck then flipped to laminate the bottom. i had done test runs on some offcuts of the timber first with no sign of any problems.

i did get a little bit of milkiness around the edges of the glass but overall it was very clear. i think the dark wood it sits over doesnt help so im planning to sand these areas out tonight and recoat.

i managed to get the hotcoats on yesterday and everything looks good.

so tonight i will sand out the 3 milky areas and recoat and also rout the finbox and set that in. unfortunatly i dont have any RR slow hardener so im gonna have to go with the fast which has been taking about 3.5hrs to set which im hoping will be ok.

it did look like the add f is the problem with the milky areas compounded by the fact it was difficult to squeegee out the excess resin at the edges of the glass without pulling loads of stringy bits out. i think in future ill be doing cutlaps to try and avoid this.

once again thanks for the inputs and ill start a new thread with build pictures.