mould release wax

[ghostlymoron]

I need to take a mould off my main hatch in order to do a repair on shattered corner. My plan is build up the corner to its original shape using pollyfiller then take a grp mould of it. The corner would then be ground out to provide a base for mat and resin, the mould re-attached and gelcoat
applied followed my mat and resin. To produce the mould I need very small quantities of materials including release wax. Is this essential or could i use car wax? Also is my repair method over complicated? Its the only way i could think of to produce a good finish on the outside.

 

[coopec]

Be careful what type of wax as some of them have additives that react with resin. I have been using tins of beeswax which is fairly soft. I have also used wax that the kids use to wax their sand boards.

 

[coopec]

Also is my repair method over complicated? Its the only way i could think of to produce a good finish. On the outside
applied

Yes I think it is too complicated. The fiberglass casting will only be as good as the mold so you'll have to spend a lot of time getting that right. Then you plan to take a mold from the built up area. Then take a f/g casting from the mold. Then attach the casting to the hatch cover. That is far too time consuming.
I suggest you grind out the shattered corner then fill the corner with a block of shaped wood, wax the wood and then lay the glass over that. You'll have to spend a bit of time finishing it off nicely. You can strengthen the corner by laying glass over the inside of the hatch.

 

[ghostlymoron]

I don't see that your method is any quicker. The corner of the hatch needs to thin so that it fits over the frame. I intended holding the mould in place using ratchet straps.
Beeswax would be good if it works as I've already got some. Is it just the shininess or is there a reaction with the resin that stops it sticking?

 

[P4Paul]

I don't see that your method is any quicker. The corner of the hatch needs to thin so that it fits over the frame. I intended holding the mould in place using ratchet straps.
Beeswax would be good if it works as I've already got some. Is it just the shininess or is there a reaction with the resin that stops it sticking?

Can you take a splash mould from the opposite corner to save time?

 

[ghostlymoron]

Having re read your reply, i think you have misunderstood my proposed method. I would create the positive shape required, then create the mould (negative), then prepare the hatch to receive a repair from the inside, attach negative mould to hatch and gel, mat and resin from the inside. Difficult to explain (specially using Android!)

Yes I think it is too complicated. The fiberglass casting will only be as good as the mold so you'll have to spend a lot of time getting that right. Then you plan to take a mold from the built up area. Then take a f/g casting from the mold. Then attach the casting to the hatch cover. That is far too time consuming.
I suggest you grind out the shattered corner then fill the corner with a block of shaped wood, wax the wood and then lay the glass over that. You'll have to spend a bit of time finishing it off nicely. You can strengthen the corner by laying glass over the inside of the hatch.

 

[ghostlymoron]

I don't know what a splash mould is. The opposite corner is slightly different :-(

Can you take a splash mould from the opposite corner to save time?

 

[P4Paul]

I don't know what a splash mould is. The opposite corner is slightly different :-(

A splash mould is a light weight mould taken solely to transfer the shape or to make a one-off moulding.

Be careful using filler as it can stick to a mould. You could use resin bulked up with talcum powder to make an easy sand filler which will release with just a few good coats of wax.

Edited to say, if you use resin and talc, make sure you catalyse the resin and stir well before adding the talc

 

[ghostlymoron]

Splash mould is the ticket then. I could use car body filler instead of pollyfiller as I've got some of that. I want something that i can sand to shape easily and takes a polish to allow easy release.

A splash mould is a light weight mould taken solely to transfer the shape or to make a one-off moulding.

Be careful using filler as it can stick to a mould. You could use resin bulked up with talcum powder to make an easy sand filler which will release with just a few good coats of wax.

Edited to say, if you use resin and talc, make sure you catalyse the resin and stir well before adding the talc

 

[P4Paul]

Splash mould is the ticket then. I could use car body filler instead of pollyfiller as I've got some of that. I want something that i can sand to shape easily and takes a polish to allow easy release.

If you want to be 100% sure of it releasing, stay away from any filler unless you put a barrier coat on top. Car body filler will stick if it is cellulose based and most fillers are porous which sucks the resin into it. Stay away from cellulose paint as a barrier coat, use a two pack or brown parcel tape or a purpose made product.

I see you are in Shropshire, I am just outside of Reading (berth in Swanwick) and happy to let you have some plug coat and tooling gel but I can't post it because the catalyst comes under hazard regulations. If you are around the Reading or Swanwick area just let me know.

 

[ghostlymoron]

Thanks Paul but I'm not often down your way. Trouble is a) i don't quite know what i need and b) i don't want to buy big quantities for such a tiny job.
There is a fibreglass molding company in shrewsbury so I'll try blagging some off them.

 

[prv]

I don't see that your method is any quicker. The corner of the hatch needs to thin so that it fits over the frame. I intended holding the mould in place using ratchet straps.

It could certainly be done quicker by laying up without a mould (perhaps just a basic support of cardboard or polystyrene wrapped in parcel tape), whacking on lots of gelcoat, and sanding to shape. This will always look like a quickie repair, though. Your plan with plug and mould is the pukka approach.

Is it just the shininess or is there a reaction with the resin that stops it sticking?

I believe it's just perfect shininess. Gelcoat doesn't stick firmly to shiny surfaces, even if you want it to

I have seen instructions saying to use car wax, so I think that's an option, but if you have beeswax and know it will give a shiny surface then it should be fine.

Pete

 

[coopec]

It could certainly be done quicker by laying up without a mould (perhaps just a basic support of cardboard or polystyrene wrapped in parcel tape), whacking on lots of gelcoat, and sanding to shape. This will always look like a quickie repair, though. Your plan with plug and mould is the pukka approach.



I believe it's just perfect shininess. Gelcoat doesn't stick firmly to shiny surfaces, even if you want it to

I have seen instructions saying to use car wax, so I think that's an option, but if you have beeswax and know it will give a shiny surface then it should be fine.

Pete

prv is absolutely correct. Forget about molds. You might as well be doing the finished job as making up molds.

I would use a block of soft scrap wood (but as pvc says it can be anything which will support the f/g layup) and cut it, sand it so that the block fitted snugly within the mold. If there are holes/dips I would fill them up with a "bog" (talc/resin/catalyst) and sand to the shape required. I give my molds two coats of wax plus two coats of PVA release agent. I would taper the edges of the hatch and then lay the glass over the damaged area and then finish it of with bog (or body putty). There are stacks of video clips on youtube showing how to do f/g repairs. Here is just one of them but you may find a more appropriate one for your sort of repair.

http://www.youtube.com/watch?v=MmDka6IwgSo

If I were you I would do your fiber glassing out in the open, wear gloves and don't get the catalyst in your eyes. ( I have been told that if you get the catalyst in your eye you have 15 seconds to wash it out)

 

[ghostlymoron]

It could certainly be done quicker by laying up without a mould (perhaps just a basic support of cardboard or polystyrene wrapped in parcel tape), whacking on lots of gelcoat, and sanding to shape. This will always look like a quickie repair, though. Your plan with plug and mould is the pukka approach.



I believe it's just perfect shininess. Gelcoat doesn't stick firmly to shiny surfaces, even if you want it to

I have seen instructions saying to use car wax, so I think that's an option, but if you have beeswax and know it will give a shiny surface then it should be fine.

Pete

I like pukka and have plenty of time. I'll take some piccies so you can see how I get on. Thanks for the advice.

 

[ghostlymoron]

prv is absolutely correct. Forget about molds. You might as well be doing the finished job as making up molds.

I would use a block of soft scrap wood (but as pvc says it can be anything which will support the f/g layup) and cut it, sand it so that the block fitted snugly within the mold. If there are holes/dips I would fill them up with a "bog" (talc/resin/catalyst) and sand to the shape required. I give my molds two coats of wax plus two coats of PVA release agent. I would taper the edges of the hatch and then lay the glass over the damaged area and then finish it of with bog (or body putty). There are stacks of video clips on youtube showing how to do f/g repairs. Here is just one of them but you may find a more appropriate one for your sort of repair.

http://www.youtube.com/watch?v=MmDka6IwgSo

If I were you I would do your fiber glassing out in the open, wear gloves and don't get the catalyst in your eyes. ( I have been told that if you get the catalyst in your eye you have 15 seconds to wash it out)

prv said 'It could certainly be done quicker by laying up without a mould (perhaps just a basic support of cardboard or polystyrene wrapped in parcel tape), whacking on lots of gelcoat, and sanding to shape. This will always look like a quickie repair, though. Your plan with plug and mould is the pukka approach.' I take that to mean he approves of my method (but wouldn't necessarily do it that way himself).

 

[nigelmercier]

Personally I would use PVA Release Agent: http://amzn.to/1lLx772

If you only need a small quantity I could send you some.

 

[prv]

prv said 'It could certainly be done quicker by laying up without a mould (perhaps just a basic support of cardboard or polystyrene wrapped in parcel tape), whacking on lots of gelcoat, and sanding to shape. This will always look like a quickie repair, though. Your plan with plug and mould is the pukka approach.' I take that to mean he approves of my method (but wouldn't necessarily do it that way himself).

Exactly so.

(Some things I've gone the full plug and mould route, others I've just laid up in situ. Depends on how big, how visible, and frankly how much I can be arsed )

Pete

 

[ghostlymoron]

I figure it won't take me long to produce the 'plug' as all I've got to do is fill the existing corner of the hatch to an ultra smooth surface The mould will likewise take very little time and the gelcoat and fibreglassing would be the same anyway. Here's a photo of the hatch as it is now.

 

[30boat]

Having looked at the photo I'm sure there are easier ways of achieving a strong and invisible repair.This is how I'do it.First grind the inside overlaping the edges of the breaks reducing the thickness of the laminate so that fresh glass and resin can be applied.Secondly after the inside laminations have cured ,clean off the exterior edges of the breaks and fill with thickened topcoat.Talcum is perfect for that.Allow to cure, sand and polish.There's no need for a mould for such a small repair.IMHO.

 

[coopec]

Having looked at the photo I'm sure there are easier ways of achieving a strong and invisible repair.This is how I'do it.First grind the inside overlaping the edges of the breaks reducing the thickness of the laminate so that fresh glass and resin can be applied.Secondly after the inside laminations have cured ,clean off the exterior edges of the breaks and fill with thickened topcoat.Talcum is perfect for that.Allow to cure, sand and polish.There's no need for a mould for such a small repair.IMHO.

Having viewed the photo of the damage it is not as bad as I had expected. That's not "shattered" it is just "cracked" in my book. (Not a big deal!)

30boat. You've obviously "been there, done that". The damage to the hatch is very similar to the damage done to the f/g bumper bar in the youtube video clip and they repaired it exactly as you suggested!.

http://www.youtube.com/watch?v=MmDka6IwgSo

Making a very good female mold of a corner of a hatch is difficult anyway as it is hard to find tools the exact diameter of the compound curves of the corner. When I do it I screed bog in one direction, let it cure then screed bog at 90 degrees and then let that cure. Then I use burrs on the end of the drill, flapper discs and sanders, finger/sanpaper etc etc. and still the mold is not perfect so I sand off the finished casting with the orbital sander.

To do that to repair the damaged corner of a hatch does not make sense