04-07-2022, 10:20 AM
Courtesy of Cbus (Col):
A lot of poptops could do with some degree of repair or refurbishment.
Hopefully the following may help.
Its not hard if a bit if care is taken & results are directly proportional to care at each stage.
This is assuming a full refurbishment. Minor repairs can be done in situ.
1. Remove poptop.
Create suitable stands so you can work at a comfortable height and poptop is supported "square".
2. Separate the sections and remove all trim and sealants.
Degrease and scrub ,rinse well.
Most likely any chipboard stiffeners will be deteriorating. Regardless, take photos to guide reassembly and remove chipboard.
Use these to cut new ones from a solid timber that will provide better strength for attachments.
SANDING FIBREGLASS.
The dust is a strong irritant.
You will itch for days if exposed and its bad for the lungs and eyes.
Wear a full disposable paper overall set and wear mask and goggles.
Silicone rubber masks are better than paper dust masks.
Ski type goggles are better for vision and comfort
You are going to need all of this for the spraying anyway so invest.
Cotton hoods are also good and comfortable.
If you do get itchy ,shower in cold water . prevents pores opening.
3. Dry sand inner with a random orbital sander using an interface pad and 120-180 grit sandpaper. 6" palm sander is good if you have a compressor that delivers closer to 300l/min.
Grey or beige aluminium oxide papers are pretty useless. blue or green ones are different and they last much longer and cut better. Especially when dealing with epoxy resins.
The aim underneath is to key the surface for a coat of epoxy and cloth. Doesn't need to be smooth but needs to be clean and hopefully around 80% or more scratched up.
For top / gelcoat. Same deal except you want it smooth and all sanded. Don't bother with sanding finer than 180dry.
You may be able to sand this without the overalls if there is no exposed fibre. Use mask tho.
4.Wipe down with a damp rag to remove dust and fibre.
Dispose rags by wrapping in old plastic bags.
Hose down work area.
Ensure all moisture is dried out of any exposed fibre or cracks.
Rinsing with acetone will absorb water. Blow out with compressed air.
Dry in the sun for a week if unsure.
5. REPAIRING DAMAGE.
For fine cracks a quality superglue is easy. You will be also sandwiching both surfaces and this gives added strength.
For cracks all way through:
You can saturate with the broken edges with mixed resin and clamp or use superglue.
Ensure top is sitting square and everything lines up
To beef up the join, scarf out about 25% thickness both sides and build up with layers of resin and cloth to original level.
Usualy scarfing would be a 7:1 ratio. In this case I would go a minimum of 25mm each side of crack on each face.
Most poptops are flimsy and irregular.
You will need to decide what finish you want.
Personally I would repair any damage and cracks then apply a minimum 100gsm ( could go heavier if desired. Up to maybe 190gsm. ) layer of woven cloth using epoxy resins.
This will help stiffen the top as well as sandwich any cracks.
New stiffeners can be glued in place with a firm paste made of epoxy resin filled with glue powder.
Details of use later
Alternately a good bond with sika will do.
Epoxy glue will prob be cheaper.
6. Glass the timbers in with a layer or two of 190gsm cloth.
190gsm woven cloth does not go around tight internal curves easily.
Usual method is radius all sharp edges to about same as 5 or 10 cent piece.
Fillet ( fill) inside corners with a glue powder mix.
Work in with brush.
7. Saturate the exposed edges of top to seal fibres.
Large crushed areas are treated same as cracks except done as a whole surface.
In this case grind off one surface so that you can saturate the core with an epoxy mix.
It may help to add up to 15% acetone to reduce viscosity and help saturation.
Once the resin has firmed but still tacky, apply another coat of resin ( it will be a fresh lot as working time is temp dependent but usualy less than 8 minutes.)
Immediately work in successive layers of cloth to about level to finished surface or a bit under.
Repeat other side.
You need to distinguish between fractures and stress cracks in the gelcoat that are caused by rough handling and hammering during removal from mold.
Such stress cracks are not structural. They often resemble spider webs with s point of impact being obvious.
The only issue with these is they can delelop thru a new cost of paint.
For this reason I would suggest a good physical key and at least a layer of 80gsm with resin before priming.
Finish the underneath as you wish but it is usualy a rough finish of chopped matt.
If just doing a repair underneath and not a full layer of woven cloth then chopped strand will better match existing surface.
Tear the edge to blend rather than cut with scissors.
I would also consider a full layer of woven on top surface. Probably 100gsm.
METHOD.
Epoxy laminating resin is a 2 part product.
Resin and hardener.
Use mixing cups to measure.
Different resins have different ratios so familiarise fully with the product chosen.
ALLWAYS download a TDS on any product.
It gives usefull info.
Typically can be from 1-1 to 4-1.
Closer ratios usualy superior but not critical for our use.
For this purpose same for brands.
Reaction is quite temp dependent.
Keep contents cool as practical.
A litre and 500ml mixing cup are a good start. Start with small mixes as you only have 5-8 minutes at about 25C.
Don't continue to use once it starts to thicken or gell.
Be accurate in measuring.
Once mixed put in a shallow container such as 4litre ice cream container. The reaction is exothermic (gives off heat..)
Shallow container allows dissipation of heat. If heat builds then working time is considerably reduced.
It can also get hot enough to cause ignition.
DO NOT dump in waste bin or allow rags soaked in mix to sit in a pile. Can cause fire.
Safe once reaction completed and cooled.
Pays to wear disposable gloves. Some people sensitive to resins.
If on skin don't wash off with acetone or thinners. These enter bloodstream quite effectively via skin.
Wash with vinegar then rinse with water.
The vinegar breaks down the resin very effectively.
Use in a ventilated area.
Concentrated vapour can kill.
If necessary ,thinning is between 5-15%.
Washing tools is with acetone.
Allow to harden in plastic containers and it can be pulled out.
Work in limited areas till familiar with use.
Cut cloth to size before mixing resin.
I usualy apply a thin surface of resin and bed the cloth into it . Applying more resin as needed to ensure cloth is saturated.
When saturated it will be clear. No signs of white fibres.
Use squeegee to remove as much resin as practical.
The less resin to cloth ratio the stronger the job.
If difficult to fit or work into corners you can allow the first coat of resin to tack of and it will hold the cloth in place. Allow another 1/4 hour then saturate with next coat and squeegee excess.
If building layers stick to 2 at a time.
To many in one hit gets difficult to squeegee out plus builds too much heat.
Wait until firm but still tacky and apply more.
If it has hardened overnight it will usualy have an amine blush.
This feels slimy to the touch.
Wipe with acetone then lightly sand prior to following coats.
It must be cleaned and sanded before filling or painting.
One exception is by spreading a light skim of mixed epoxy resin and Q cells or microlight over a cured but still tacky resin. Usualy a hour or few hours after resin applied.
This gives an easily sanded surface ready for painting.
Additional filler can go straight over if needed.
Q cells and microlight are filler powders that are added to micedvresin to form a filler like bog.
The more powder in the mix the easier it is to sand.
Straight epoxy is very hard to sand.
Another method of easy prep for next process is using peel ply.
This is like fine curtain mesh that is squeegeed into last cost of resin.
Next day it is peeled off and removes extra resin along with amine plus leaves a rough finish ready for next process .
If sanding thru epoxy exposes cloth fibres they should be encapsulated with some fresh resin before proceeding.
Epoxy resin is completely waterproof. Sanded filler should have a coat of resin applied and if desired squegeed off to leave a seal.
Same applies to the top if you choose not to apply a layer of cloth.
A layer of resin that is then squeegeed off and allowed to go till still retaining a dry tac is good for next coat of epoxy primer.
Not essential tho.
Epoxy primer can go straight over the sanded surface.
A lot of poptops could do with some degree of repair or refurbishment.
Hopefully the following may help.
Its not hard if a bit if care is taken & results are directly proportional to care at each stage.
This is assuming a full refurbishment. Minor repairs can be done in situ.
1. Remove poptop.
Create suitable stands so you can work at a comfortable height and poptop is supported "square".
2. Separate the sections and remove all trim and sealants.
Degrease and scrub ,rinse well.
Most likely any chipboard stiffeners will be deteriorating. Regardless, take photos to guide reassembly and remove chipboard.
Use these to cut new ones from a solid timber that will provide better strength for attachments.
SANDING FIBREGLASS.
The dust is a strong irritant.
You will itch for days if exposed and its bad for the lungs and eyes.
Wear a full disposable paper overall set and wear mask and goggles.
Silicone rubber masks are better than paper dust masks.
Ski type goggles are better for vision and comfort
You are going to need all of this for the spraying anyway so invest.
Cotton hoods are also good and comfortable.
If you do get itchy ,shower in cold water . prevents pores opening.
3. Dry sand inner with a random orbital sander using an interface pad and 120-180 grit sandpaper. 6" palm sander is good if you have a compressor that delivers closer to 300l/min.
Grey or beige aluminium oxide papers are pretty useless. blue or green ones are different and they last much longer and cut better. Especially when dealing with epoxy resins.
The aim underneath is to key the surface for a coat of epoxy and cloth. Doesn't need to be smooth but needs to be clean and hopefully around 80% or more scratched up.
For top / gelcoat. Same deal except you want it smooth and all sanded. Don't bother with sanding finer than 180dry.
You may be able to sand this without the overalls if there is no exposed fibre. Use mask tho.
4.Wipe down with a damp rag to remove dust and fibre.
Dispose rags by wrapping in old plastic bags.
Hose down work area.
Ensure all moisture is dried out of any exposed fibre or cracks.
Rinsing with acetone will absorb water. Blow out with compressed air.
Dry in the sun for a week if unsure.
5. REPAIRING DAMAGE.
For fine cracks a quality superglue is easy. You will be also sandwiching both surfaces and this gives added strength.
For cracks all way through:
You can saturate with the broken edges with mixed resin and clamp or use superglue.
Ensure top is sitting square and everything lines up
To beef up the join, scarf out about 25% thickness both sides and build up with layers of resin and cloth to original level.
Usualy scarfing would be a 7:1 ratio. In this case I would go a minimum of 25mm each side of crack on each face.
Most poptops are flimsy and irregular.
You will need to decide what finish you want.
Personally I would repair any damage and cracks then apply a minimum 100gsm ( could go heavier if desired. Up to maybe 190gsm. ) layer of woven cloth using epoxy resins.
This will help stiffen the top as well as sandwich any cracks.
New stiffeners can be glued in place with a firm paste made of epoxy resin filled with glue powder.
Details of use later
Alternately a good bond with sika will do.
Epoxy glue will prob be cheaper.
6. Glass the timbers in with a layer or two of 190gsm cloth.
190gsm woven cloth does not go around tight internal curves easily.
Usual method is radius all sharp edges to about same as 5 or 10 cent piece.
Fillet ( fill) inside corners with a glue powder mix.
Work in with brush.
7. Saturate the exposed edges of top to seal fibres.
Large crushed areas are treated same as cracks except done as a whole surface.
In this case grind off one surface so that you can saturate the core with an epoxy mix.
It may help to add up to 15% acetone to reduce viscosity and help saturation.
Once the resin has firmed but still tacky, apply another coat of resin ( it will be a fresh lot as working time is temp dependent but usualy less than 8 minutes.)
Immediately work in successive layers of cloth to about level to finished surface or a bit under.
Repeat other side.
You need to distinguish between fractures and stress cracks in the gelcoat that are caused by rough handling and hammering during removal from mold.
Such stress cracks are not structural. They often resemble spider webs with s point of impact being obvious.
The only issue with these is they can delelop thru a new cost of paint.
For this reason I would suggest a good physical key and at least a layer of 80gsm with resin before priming.
Finish the underneath as you wish but it is usualy a rough finish of chopped matt.
If just doing a repair underneath and not a full layer of woven cloth then chopped strand will better match existing surface.
Tear the edge to blend rather than cut with scissors.
I would also consider a full layer of woven on top surface. Probably 100gsm.
METHOD.
Epoxy laminating resin is a 2 part product.
Resin and hardener.
Use mixing cups to measure.
Different resins have different ratios so familiarise fully with the product chosen.
ALLWAYS download a TDS on any product.
It gives usefull info.
Typically can be from 1-1 to 4-1.
Closer ratios usualy superior but not critical for our use.
For this purpose same for brands.
Reaction is quite temp dependent.
Keep contents cool as practical.
A litre and 500ml mixing cup are a good start. Start with small mixes as you only have 5-8 minutes at about 25C.
Don't continue to use once it starts to thicken or gell.
Be accurate in measuring.
Once mixed put in a shallow container such as 4litre ice cream container. The reaction is exothermic (gives off heat..)
Shallow container allows dissipation of heat. If heat builds then working time is considerably reduced.
It can also get hot enough to cause ignition.
DO NOT dump in waste bin or allow rags soaked in mix to sit in a pile. Can cause fire.
Safe once reaction completed and cooled.
Pays to wear disposable gloves. Some people sensitive to resins.
If on skin don't wash off with acetone or thinners. These enter bloodstream quite effectively via skin.
Wash with vinegar then rinse with water.
The vinegar breaks down the resin very effectively.
Use in a ventilated area.
Concentrated vapour can kill.
If necessary ,thinning is between 5-15%.
Washing tools is with acetone.
Allow to harden in plastic containers and it can be pulled out.
Work in limited areas till familiar with use.
Cut cloth to size before mixing resin.
I usualy apply a thin surface of resin and bed the cloth into it . Applying more resin as needed to ensure cloth is saturated.
When saturated it will be clear. No signs of white fibres.
Use squeegee to remove as much resin as practical.
The less resin to cloth ratio the stronger the job.
If difficult to fit or work into corners you can allow the first coat of resin to tack of and it will hold the cloth in place. Allow another 1/4 hour then saturate with next coat and squeegee excess.
If building layers stick to 2 at a time.
To many in one hit gets difficult to squeegee out plus builds too much heat.
Wait until firm but still tacky and apply more.
If it has hardened overnight it will usualy have an amine blush.
This feels slimy to the touch.
Wipe with acetone then lightly sand prior to following coats.
It must be cleaned and sanded before filling or painting.
One exception is by spreading a light skim of mixed epoxy resin and Q cells or microlight over a cured but still tacky resin. Usualy a hour or few hours after resin applied.
This gives an easily sanded surface ready for painting.
Additional filler can go straight over if needed.
Q cells and microlight are filler powders that are added to micedvresin to form a filler like bog.
The more powder in the mix the easier it is to sand.
Straight epoxy is very hard to sand.
Another method of easy prep for next process is using peel ply.
This is like fine curtain mesh that is squeegeed into last cost of resin.
Next day it is peeled off and removes extra resin along with amine plus leaves a rough finish ready for next process .
If sanding thru epoxy exposes cloth fibres they should be encapsulated with some fresh resin before proceeding.
Epoxy resin is completely waterproof. Sanded filler should have a coat of resin applied and if desired squegeed off to leave a seal.
Same applies to the top if you choose not to apply a layer of cloth.
A layer of resin that is then squeegeed off and allowed to go till still retaining a dry tac is good for next coat of epoxy primer.
Not essential tho.
Epoxy primer can go straight over the sanded surface.
(04-07-2022, 10:20 AM)Oldman Wrote: Courtesy of Cbus (Col):
A lot of poptops could do with some degree of repair or refurbishment.
Hopefully the following may help.
Its not hard if a bit if care is taken & results are directly proportional to care at each stage.
This is assuming a full refurbishment. Minor repairs can be done in situ.
1. Remove poptop.
Create suitable stands so you can work at a comfortable height and poptop is supported "square".
2. Separate the sections and remove all trim and sealants.
Degrease and scrub ,rinse well.
Most likely any chipboard stiffeners will be deteriorating. Regardless, take photos to guide reassembly and remove chipboard.
Use these to cut new ones from a solid timber that will provide better strength for attachments.
SANDING FIBREGLASS.
The dust is a strong irritant.
You will itch for days if exposed and its bad for the lungs and eyes.
Wear a full disposable paper overall set and wear mask and goggles.
Silicone rubber masks are better than paper dust masks.
Ski type goggles are better for vision and comfort
You are going to need all of this for the spraying anyway so invest.
Cotton hoods are also good and comfortable.
If you do get itchy ,shower in cold water . prevents pores opening.
3. Dry sand inner with a random orbital sander using an interface pad and 120-180 grit sandpaper. 6" palm sander is good if you have a compressor that delivers closer to 300l/min.
Grey or beige aluminium oxide papers are pretty useless. blue or green ones are different and they last much longer and cut better. Especially when dealing with epoxy resins.
The aim underneath is to key the surface for a coat of epoxy and cloth. Doesn't need to be smooth but needs to be clean and hopefully around 80% or more scratched up.
For top / gelcoat. Same deal except you want it smooth and all sanded. Don't bother with sanding finer than 180dry.
You may be able to sand this without the overalls if there is no exposed fibre. Use mask tho.
4.Wipe down with a damp rag to remove dust and fibre.
Dispose rags by wrapping in old plastic bags.
Hose down work area.
Ensure all moisture is dried out of any exposed fibre or cracks.
Rinsing with acetone will absorb water. Blow out with compressed air.
Dry in the sun for a week if unsure.
5. REPAIRING DAMAGE.
For fine cracks a quality superglue is easy. You will be also sandwiching both surfaces and this gives added strength.
For cracks all way through:
You can saturate with the broken edges with mixed resin and clamp or use superglue.
Ensure top is sitting square and everything lines up
To beef up the join, scarf out about 25% thickness both sides and build up with layers of resin and cloth to original level.
Usualy scarfing would be a 7:1 ratio. In this case I would go a minimum of 25mm each side of crack on each face.
Most poptops are flimsy and irregular.
You will need to decide what finish you want.
Personally I would repair any damage and cracks then apply a minimum 100gsm ( could go heavier if desired. Up to maybe 190gsm. ) layer of woven cloth using epoxy resins.
This will help stiffen the top as well as sandwich any cracks.
New stiffeners can be glued in place with a firm paste made of epoxy resin filled with glue powder.
Details of use later
Alternately a good bond with sika will do.
Epoxy glue will prob be cheaper.
6. Glass the timbers in with a layer or two of 190gsm cloth.
190gsm woven cloth does not go around tight internal curves easily.
Usual method is radius all sharp edges to about same as 5 or 10 cent piece.
Fillet ( fill) inside corners with a glue powder mix.
Work in with brush.
7. Saturate the exposed edges of top to seal fibres.
Large crushed areas are treated same as cracks except done as a whole surface.
In this case grind off one surface so that you can saturate the core with an epoxy mix.
It may help to add up to 15% acetone to reduce viscosity and help saturation.
Once the resin has firmed but still tacky, apply another coat of resin ( it will be a fresh lot as working time is temp dependent but usualy less than 8 minutes.)
Immediately work in successive layers of cloth to about level to finished surface or a bit under.
Repeat other side.
You need to distinguish between fractures and stress cracks in the gelcoat that are caused by rough handling and hammering during removal from mold.
Such stress cracks are not structural. They often resemble spider webs with s point of impact being obvious.
The only issue with these is they can delelop thru a new cost of paint.
For this reason I would suggest a good physical key and at least a layer of 80gsm with resin before priming.
Finish the underneath as you wish but it is usualy a rough finish of chopped matt.
If just doing a repair underneath and not a full layer of woven cloth then chopped strand will better match existing surface.
Tear the edge to blend rather than cut with scissors.
I would also consider a full layer of woven on top surface. Probably 100gsm.
METHOD.
Epoxy laminating resin is a 2 part product.
Resin and hardener.
Use mixing cups to measure.
Different resins have different ratios so familiarise fully with the product chosen.
ALLWAYS download a TDS on any product.
It gives usefull info.
Typically can be from 1-1 to 4-1.
Closer ratios usualy superior but not critical for our use.
For this purpose same for brands.
Reaction is quite temp dependent.
Keep contents cool as practical.
A litre and 500ml mixing cup are a good start. Start with small mixes as you only have 5-8 minutes at about 25C.
Don't continue to use once it starts to thicken or gell.
Be accurate in measuring.
Once mixed put in a shallow container such as 4litre ice cream container. The reaction is exothermic (gives off heat..)
Shallow container allows dissipation of heat. If heat builds then working time is considerably reduced.
It can also get hot enough to cause ignition.
DO NOT dump in waste bin or allow rags soaked in mix to sit in a pile. Can cause fire.
Safe once reaction completed and cooled.
Pays to wear disposable gloves. Some people sensitive to resins.
If on skin don't wash off with acetone or thinners. These enter bloodstream quite effectively via skin.
Wash with vinegar then rinse with water.
The vinegar breaks down the resin very effectively.
Use in a ventilated area.
Concentrated vapour can kill.
If necessary ,thinning is between 5-15%.
Washing tools is with acetone.
Allow to harden in plastic containers and it can be pulled out.
Work in limited areas till familiar with use.
Cut cloth to size before mixing resin.
I usualy apply a thin surface of resin and bed the cloth into it . Applying more resin as needed to ensure cloth is saturated.
When saturated it will be clear. No signs of white fibres.
Use squeegee to remove as much resin as practical.
The less resin to cloth ratio the stronger the job.
If difficult to fit or work into corners you can allow the first coat of resin to tack of and it will hold the cloth in place. Allow another 1/4 hour then saturate with next coat and squeegee excess.
If building layers stick to 2 at a time.
To many in one hit gets difficult to squeegee out plus builds too much heat.
Wait until firm but still tacky and apply more.
If it has hardened overnight it will usualy have an amine blush.
This feels slimy to the touch.
Wipe with acetone then lightly sand prior to following coats.
It must be cleaned and sanded before filling or painting.
One exception is by spreading a light skim of mixed epoxy resin and Q cells or microlight over a cured but still tacky resin. Usualy a hour or few hours after resin applied.
This gives an easily sanded surface ready for painting.
Additional filler can go straight over if needed.
Q cells and microlight are filler powders that are added to micedvresin to form a filler like bog.
The more powder in the mix the easier it is to sand.
Straight epoxy is very hard to sand.
Another method of easy prep for next process is using peel ply.
This is like fine curtain mesh that is squeegeed into last cost of resin.
Next day it is peeled off and removes extra resin along with amine plus leaves a rough finish ready for next process .
If sanding thru epoxy exposes cloth fibres they should be encapsulated with some fresh resin before proceeding.
Epoxy resin is completely waterproof. Sanded filler should have a coat of resin applied and if desired squegeed off to leave a seal.
Same applies to the top if you choose not to apply a layer of cloth.
A layer of resin that is then squeegeed off and allowed to go till still retaining a dry tac is good for next coat of epoxy primer.
Not essential tho.
Epoxy primer can go straight over the sanded surface.
Quote:EDIT. Would be wary about large or thick applications of bog, (fibreglass filler), due to the flexibility of the thin build of poptops.
Bog is likely to crack if flexed too much.
Might need to stiffen first with stiffening panels of sandwiched foam or light wood. Being careful about added weight affecting spring operation.
Stiffener sections would likely remove much of any sag in panels due to thin construction.
Can use a self levelling finishing bog over that if desired but its expensive.
High build epoxy is harder to sand than auto high builds but easily half the price. Just a maybe.
Final primer can be heavy wet on wet.
Poly U 400 is a common top coat for boats and busses etc. Better resistance to chalking than gelcoat.
Or go up a notch and use something like Jotun Imperite.
Hard as hell and still flexible.
Beats anything automotive.
Slow flash off as is necessary for doing boats ,trucks etc so good finish off the gun and no compounding.
Epoxy primer about $100 / 4l.kit.
Imperite. About $200-250 for 5l kit
Dedicated reducer approx $60/4l.
Just options.