Fibreglass sail boat bulkhead repairs

[Islander71]

If you are using normal polyester resin you want to create a mechanical key to the old stuff, a boatbuilder friend said the best way is to use a rotary wire brush on the old fibreglass till you see strands of the glass - the new resin and glass will bond well to that.

 

[RichardM]

Can you create a control zone to grind in, big cardboard box with the vacuum taped into to suck the dust away. Worth thinking about if you are doing it internally.

 

[Pigeon_Droppings2]

I'm going to sheet off the cabin of the boat I think....the deck has a few storage compartments which can be opened up but I still think it's going to be a bit grim working in a confined space with fibreglass dust everywhere.

 

[Keith 66]

Fibreglass epoxy resin is essentially all the same.

Maybe unless your building carbonfibre super racing vessels.

Unfortunately resins are not all the same. I spent my career building & repairing GRP boats from old thick chopped strand mat hulls to carbon fibre etc.
For most repairs on old boats using Epoxy is overkill & simply not economically justifiable. Polyester comes in two flavours Orthopthalic (cheaper) & Isophthalic more expensive, the latter is higher quality & more restistant to chemicals. For 99% of GRP repairs it will be fine unless someone has used epoxy before!
The key to good bonding is long feathered edges & i use 36 or 40 grit sanding discs for grinding, As soon as they go dull change them, If you dont you will tend to polish the surface & encourage poor bonding. Keep things clean & dust vacummed up, Bonding to old oily bilge dirt isnt good!
Did i tell you the dust is bad for you? Its Glass ie Silica, I have known several boatbuilders who died of dust related diseases so wear a decent mask.
And you will itch for days until you become used to it!
The epoxy fans will cite Its increased bonding strength but it is also far more finicky to use, You cannot risk cold or falling temperatures or amine blush happens which means bad bonds, resin to hardener ratios need to be spot on & if you get it wrong it will fail.
In critical areas i often use Vinylester which is a fine compromise offering the ease of use of polyester (& same peroxide catalyst) but with properties similar to epoxy.
Some of the grinding jobs i did were unreal, two of us going at it for 5 or 6 hours with two grinders each to allow one to cool down.
Dust under the boat 4" deep like snow. This i why i always wore a damn good respirator.
I got rather good at it but dont miss it one bit!

 

[Turbo]

If you are working in a confined space you need a flow of air through it. No point in having a fan sucking out the dust or fumes if you don't have another fan blowing in fresh air.

Also take care where you are blowing the dusty air. If you are working in a boatyard or marina your neighbours will not be happy if you cover their yacht in fibreglass dust.

The ideal thing would be a high flow dust extractor like this for example.

https://www.axminstertools.com/axmi...FsD-jhruWwVuEkUqZzQ9YRuCmGbaeISBoCq14QAvD_BwE

I used a similar one when I was grinding the old paint and rust from the inside of a steel tank. I attached the hose to a welding magnet and stuck it to the tank near where I was working.

 

[Pigeon_Droppings2]

Visited the boat today so I have a few pics. These are of the starboard rear deck. The ply is well gone in most places I checked.

 

[addjunkie]

Visited the boat today so I have a few pics. These are of the starboard rear deck. The ply is well gone in most places I checked.

That looks a nice dark hole to be wielding power tools, a sawzall would get the big chunk out, long bendy blade…Is that under the cockpit locker?

What yacht is it?

 

[Pigeon_Droppings2]

I reckon if I give it a kick most of it will come out...it's really rotten for sure. It's a Friendship 22 cruiser...made in the Netherlands I believe.

I know very little about boat repairs...if I kick out all these stiffeners will it all collapse?

I'll draw a diagram when I get a moment.

 

[Pigeon_Droppings2]

The plan tmrw is to start removing the rear stiffeners (1,2,3,4,5). I will most likely start with 2 as that looks the most difficult.

One question I had was whether it matters if I use full lengths or just replace each section. It looks like they were originally put in as separate sections but I won't know for sure until I get started.

 

[addjunkie]

I reckon if I give it a kick most of it will come out...it's really rotten for sure. It's a Friendship 22 cruiser...made in the Netherlands I believe.

I know very little about boat repairs...if I kick out all these stiffeners will it all collapse?

I'll draw a diagram when I get a moment.

I doubt it will all collapse, fibreglass is very resilient stuff. How about this for an idea.

Cut bulk out with a sawzall. Then witha long blade in the same saw. Lay a sheet of thin metal on the opposite side, held in place with glue from a glue gun or duct tape. Then cut closet to the hull with the blade end running on the metal to stop it cutting the hull. Shouldnt be too much flying dust using a sawzall rather than a grinder. Worst case scenario you hole it, then you will learn how to-fix holes and repair gelcoat.

 

[Keith 66]

Stiffeners in hulls or on the underside of decks can be made of timber glassed in, in which case the timber imparts some structural strength or they can be made of sections of timber with saw cuts nearly all the way through so it will bend easily. Or you can use a foam core which just provides the shape with the strength coming from the shape itself. Dont try to use Polystyrene as the resin will melt it. Polyurethane like Celotex or similar makes good cores & is easy to work. Put a decent radius on corners & stick in place with a blob of body filler. Or you can glass over old rope laid in place but it may look rough.
When Glassing in bits like this many will tell you to cut chopped strand mat with scissors & apply the resin with a stippling action to work the resin into the mat.
Nobody who has ever worked in a production real world will fart about like this! As someone said on here a few months ago "When the slurm starts to kick off you gotta move!"
I was taught this method, Cut all your glass to size before you start, If glassing in stringers or bulkheads have a good pile of rectangular strips to go round the item plus 2" each side, In a corner like a bulkhead use strips about 4-5" wide. Make sure you bulkhead surface is sanded roughly with your grinder & heavy sanding disc. Apply a coat of catalysed resin to wooden or foam surfaces first & let it kick off before you go for it. (This lessens the risk of air bubbles & pockets) You will need a 3" brush & a paddlewheel roller & a wetting out board, this can be any old bit of cardboard or plywood as long as its clean & needs to be about 18" x 2ft" but isnt critical.
Get some old tupperware or ice cream containers to mix the resin in. Weigh out a liter & mark the outside of the containers with a marker pen, that way you know how much resin to pour out each time. Its worth buying a dispenser to measure the Catalyst, Add Catalyst at the required amount usually 1- 2% by weight, so if you have 1 liter of resin you will need between 10 & 20ccs of Catalyst, Mix it in well, The Slurm will change colour from a nice light pinky purple colour to a brownish colour, It is now show time!
Gloves on? Take your brush in one hand two pieces of glass from the stack in the other & lay them on your wetting out board keeping hold of the corners.
Slop resin on all over, then flip over & slop more on the other side, DO NOT STIPPLE IT , Lay the wetted out pieces where they are to go, repeat wetting out more pieces & slap them in place, (The mat itself is held together with a binder that is dissolved by the resin & this takes about 30 seconds).
When you have done a run about 3ft long take your roller & roll the gooey matt into place, go quickly young man as the clock is ticking, the roller rolls out the air & consolidates the laminate. If the mat has white areas add more resin & roll more.
You will need a gallon of acetone to wash brushes & your roller with & its a good idea to put some in a deep container with lid to stop it evaporating.

Safety, Catalyst is a Peroxide & is nasty stuff, Get it in your eye & its hospital time.
Resin will burn you, you usually find this out some minutes after going for a pee!
Acetone, Resin, Catalyst are all exceedingly inflammable & will burn like you would not believe.
Keep areas clean, If you mop up spills with rags dont leave them lying about as they can catch fire especially in the sun.

If you should put too much catalyst in & we have all done it, The Slurm will get very hot & start to crackle & pop alarmingly while gassing off white Styrene fumes , put the container outside somewhere safe where it can do its thing.
Styrene fumes are not good & have varying effects, most moulders i knew were quite insane as you had to be to do it for a living!

Happy itching!

 

[Turbo]

Take a few measurements before you start and make a few vertical supports from 3x3 with ply on the end to spread the load.

 

[addjunkie]

Stiffeners in hulls or on the underside of decks can be made of timber glassed in, in which case the timber imparts some structural strength or they can be made of sections of timber with saw cuts nearly all the way through so it will bend easily. Or you can use a foam core which just provides the shape with the strength coming from the shape itself. Dont try to use Polystyrene as the resin will melt it. Polyurethane like Celotex or similar makes good cores & is easy to work. Put a decent radius on corners & stick in place with a blob of body filler. Or you can glass over old rope laid in place but it may look rough.
When Glassing in bits like this many will tell you to cut chopped strand mat with scissors & apply the resin with a stippling action to work the resin into the mat.
Nobody who has ever worked in a production real world will fart about like this! As someone said on here a few months ago "When the slurm starts to kick off you gotta move!"
I was taught this method, Cut all your glass to size before you start, If glassing in stringers or bulkheads have a good pile of rectangular strips to go round the item plus 2" each side, In a corner like a bulkhead use strips about 4-5" wide. Make sure you bulkhead surface is sanded roughly with your grinder & heavy sanding disc. Apply a coat of catalysed resin to wooden or foam surfaces first & let it kick off before you go for it. (This lessens the risk of air bubbles & pockets) You will need a 3" brush & a paddlewheel roller & a wetting out board, this can be any old bit of cardboard or plywood as long as its clean & needs to be about 18" x 2ft" but isnt critical.
Get some old tupperware or ice cream containers to mix the resin in. Weigh out a liter & mark the outside of the containers with a marker pen, that way you know how much resin to pour out each time. Its worth buying a dispenser to measure the Catalyst, Add Catalyst at the required amount usually 1- 2% by weight, so if you have 1 liter of resin you will need between 10 & 20ccs of Catalyst, Mix it in well, The Slurm will change colour from a nice light pinky purple colour to a brownish colour, It is now show time!
Gloves on? Take your brush in one hand two pieces of glass from the stack in the other & lay them on your wetting out board keeping hold of the corners.
Slop resin on all over, then flip over & slop more on the other side, DO NOT STIPPLE IT , Lay the wetted out pieces where they are to go, repeat wetting out more pieces & slap them in place, (The mat itself is held together with a binder that is dissolved by the resin & this takes about 30 seconds).
When you have done a run about 3ft long take your roller & roll the gooey matt into place, go quickly young man as the clock is ticking, the roller rolls out the air & consolidates the laminate. If the mat has white areas add more resin & roll more.
You will need a gallon of acetone to wash brushes & your roller with & its a good idea to put some in a deep container with lid to stop it evaporating.

Safety, Catalyst is a Peroxide & is nasty stuff, Get it in your eye & its hospital time.
Resin will burn you, you usually find this out some minutes after going for a pee!
Acetone, Resin, Catalyst are all exceedingly inflammable & will burn like you would not believe.
Keep areas clean, If you mop up spills with rags dont leave them lying about as they can catch fire especially in the sun.

If you should put too much catalyst in & we have all done it, The Slurm will get very hot & start to crackle & pop alarmingly while gassing off white Styrene fumes , put the container outside somewhere safe where it can do its thing.
Styrene fumes are not good & have varying effects, most moulders i knew were quite insane as you had to be to do it for a living!

Happy itching!

Your really selling the fibreglass technician career options!

 

[Turbo]

Carefully plan your cutting and reassembly. Work away from then back toward your access points.
Don't want to paint yourself into a corner!
Make your templates before cutting anything out if you can.
Where ply is meeting ply join with some 2x2 timber screwed and glued in place. Use a waterproof glue like d4 or cascamite and pressure treated timber.

 

[pedrobedro]

Styrene fumes are not good & have varying effects, most moulders i knew were quite insane as you had to be to do it for a living!

There was a firm where I go walking that made architectural fibreglass structures and you could almost get high just going past. You could hear them inside working away as they were all completely shouty mad bonkers.

 

[Newlands]

Some years ago now I replaced the mast beam in my boat:
LINK
Personally I wouldn’t use an angle grinder - way too much nasty dust and glass fibres. I used a multi tool and a dremel with a little cut off disc, much easier to control with one hand while the other one holds the vacuum cleaner nozzle. I also used epoxy and woven glass cloth for all the patching and repairs. I know some people reckon that polyester resin is ok, but the fact is that it just doesn’t stick to old cured grp as well as epoxy.

 

[Keith 66]

In answer to that, Any big areas need a grinder, i often have a big vac cleaner hose running next to the grinder. Dust is a fact of life & if you dont prep it well life will get hard. Epoxy will stick well to most things. However it has limitations, Mix ratios are fixed & have to be exact & it is not tolerant of contamination. In addition it likes it to be warm 21 degrees C minimum, thats Surface temperature where you are working not air temperature.
If its colder or the temperature falls during the cure you will get Amine blush on the surface, this is a waxy by product of the slowed reaction & stays on the surface, It feels greasy to the touch & in bad cases will appear milky. Nothing put on top of it will stick properly ever. So you have to wash it off with detergent & water. You cant sand it off as that just rubs it in.

Other aspect is the reinforcement, Chopped strand mat has a binder to hold it together that is dissolved by the resin, It is usually an emulsion & most mat sold will be unsuitable for use with epoxy, You can get powder bound mat for use with epoxy.

Cost, Epoxy (West) is £151 inc vat for 6Kgs A good Polyester is £93.50 for 25kgs, Vinylester is £50 for 5kgs. (East coast fibreglass are my go to suppliers)
So Epoxy 5 times the cost. On anything but a high end boat it simply isnt worth it & the risk of a poorly done repair is actually higher, (I have had to redo several done by others).
I will use Polyester & Vinylester on occasion because they are compatible & work well. Both are far more tolerant of poor working conditions.
Best thing you can get is a 250 watt Infra red lamp (Poultry or Puppies) To hang over your work area. Warms the surface & makes life easy!

 

[Pigeon_Droppings2]

Thanks for all the input, as usual it's amazing how much knowledge is on here.

What's been very useful is giving me an idea of the amount of work that's going to be involved.

There isn't really a lot of room in the compartments and I think a lot of the work will basically involve me being trapped on my back with a grinder while fibreglass dust falls on me.

I'm going to think on it today before I start anything...I've no doubt I can do the repair...just need to decide if I really want to do it!

 

[Misterg]

if I kick out all these stiffeners will it all collapse?

Probably not, but it *may* sag. Be careful if the sections you're taking out are anywhere near the stands holding the boat up - If there's a lot of pressure on the stand, the hull can deform locally when you take the internal stiffener away. If you don't notice (and adjust the prop), you'll bake the shape into the hull when you glass in the new bulkhead. For this reason, I'd try to do it in two or more stages - certainly don't take the main bulkhead (8) out at the same time as everything else.

Our first boat (22') had failed bonding and some rotten ply bulkheads (and a detached 'floor'). On this one, the bonding could be split off fairly cleanly by driving the chisel into the joint between the bonding strips and the main hull moulding (it was only a couple of layers of CSM). You *may* be able to do similar - it's a lot less dusty than a grinder. If the original bonding is still well attached to the hull, then leave it there and cut the bonding where the ply meets the hull. You will need to use a grinder (or similar) to prepare the surfaces that the new bonding will be glassed to.

Finding decent ply for the replacements is a challenge (or very expensive). I don't think there's any merit in trying to fit fewer, larger pieces.

FWIW, I used West epoxy and powder bonded chopped strand mat for the repair and would do the same again. I don't dispute any of Keith 66's comments above regarding polyester, etc. For bonding in bulkheads in a small boat, you'll probably do all of the layup (in any one area) in one session, so you won't have to worry about amine blush, and even if not, It can be removed with a quick scrub using a scouring pad / scotchbrite and soapy water if you do want to bond to it. Something you would want to avoid in a commercial setting, but for DIY, it's no big deal. If you do go with epoxy, it's worth getting the metering pumps to get an accurate mix easily. (Mix 'little & often' as it goes off quickly.)

It'll take longer than you think

 

[Keith 66]

Regarding poor access, Sometimes its easier to cut a deck panel or similar away so you can get at an area easily, Do the grinding the easy way, fix & stick the deck back & repair the join, No percentage cramming yourself into a confined space with a grinder!