Injecting fibreglass resin.

[paulcooper]

The foredeck on my boat has hollow sounding patches between the presumed balsa sandwich deck and cabin ceiling.

Have been advised to drill holes in the top deck and inject resin into the voids.

Anyone done this job and what is the best way to inject mixed resin to ensure it reaches the surrounding area before it hardens?
It already sounds like a messy job so would be grateful for any tips.

Or is there a better solution?

All ideas considered but have you done this job with success?

Thanks in advance. Paul.

 

[Poignard]

Section 5.1.3 of this WEST handbook deals with this problem

http://www.westsystem.com/ss/assets/HowTo-Publications/Fiberglass-Boat-Repair-and-Maintenance.pdf

 

[Travelmate]

Balsa Deck

The most important process is to dry the balsa thoroughly. This is the same problem we had on our foredeck. Most of our time is spent in the tropical waters of Malaysia & Borneo.
Drilled quite a number of holes in the foredeck (from inside the cabin) that were about 12mm Dia. and 30mm apart. Used a fairly powerful vacuum cleaners to make sure we had air flow through the affected deck area. Also used a scibe to rid the area of defective Balsa. Once the area was dry then used 12mm dowling cut a little shorter than the Balsa and used epoxy to fill the void using a syringe then forced the dowling into the hole. You may need to use several pieces of dowling if the area of balsa removed is quite large. This has a double effect of retaining the epoxy and also lending some strength to the area where the balsa is defective.

Used masking tape around all the holes to ensure epoxy did not spread around unwanted
areas then used "cling wrap" (kitchen wrap) over the holes that again was held in place with masking tape. If the epoxy mix is strengthened with microfibre than it is fairly non sag as well as a more effective resin.

The other method is to remove a section of deck completely and replace the affected core material. OK is the result is not subject to cosmetic inspection

Our method worked well as the out deck is teak and the underside is covered with lining.

All the best
Tony

 

[boatmike]

This is indeed difficult. If you know the size of the patches one way is to drill several holes around the periphery of the area just big enough for a tight fit on a piece of plastic pipe. Join the plastic pipes up to a central manifold and apply vacuum. (Pela oil extraction thingies are ideal for this) Then drill a hole in the middle big enough to jam a funnel in. Now in theory, if done right, the resin should be poured into the funnel and vacuum applied with the pela should suck the resin in and up the pipes outside. As soon as resin appears up one pipe put a clip on it and continue in turn until it comes up all the pipes. Then remove the pela and allow to cure.... Simples!! Not a bad idea to try it out with liquid styrene or similar before using catalysed resin to make sure you have a flow path. Remember that "injecting" resin won't work unless air can escape anyway and most injected solutions don't do any better than cause a local penny washer sized repair.

 

[oldsaltoz]

Composite deck failure:

This problem is normally done from the underside of the deck to preserve the appearance of the outer finish.

We have done a few of these over years and had no further problems the steps are as follows.

Remove what you can from below the effected area and cover with plastic sheeting to protect it, ensure the rest of the walking area right to the step off point is also protected.

Tapping on the overhead glass will give some idea of the size and location of the area to be treated, solid will areas will return a higher and sharper note, soft areas will have a duller, lower sound.

Using a 6 mm drill fitted with a depth stopper, drill holes at 30 mm intervals and check the material that comes out of the drill flutes for any sign of moisture, make a mark next to each hole to indicate if it is wet of dry.

Extend out till you get two dry holes next to each other all the way round.

Now you can play join the dots on all the outer holes marked wet, this will indicate the size of the problem to be treated.

Use an angle grinder to remove the section of class being very careful not to cut the upper deck layer.

Now remove this section, a large screwdriver of chisel is good to get a few fingers in and pull down.

Check all exposed edges of the core material and remove any and all material showing any sign of dampness, you will also have to remove about 25 mm of the material that outside the grinder cut leaving a small ledge all round (more on this later).

Check again to ensure everything is dry, this is very important as any moisture left behind will be trapped and will cause more problems down the track.

Now wipe the underside of the upper deck with some Acetone before you start to clean it, this helps remove any contamination that would otherwise be spread when sanding clean. After all sanding is finishes wash the whole area again with Acetone.

Make a template of the area to be replaced, cut this in half at the narrowest point and push each half in above the shelf and make sure it fits with a small amount of movement, but not tight at any point.

Now you have a pattern you can cut your replacement material to shape; you can use more Balsa, closed cell structural foam, closed cell balloons or Klegacell (my favourite); avoid ply unless epoxy treated.

Cut you material to shape and dry fit to ensure a small gap all round and the centre cut has a good joint. If you need to curve the fill material you can: For foam cut slots almost right through using a wood hand saw with a wide set on the teeth, keep the slots close for tighter bends or curves. For Klegacell laminate to the required depth, after laying some cling wrap over the job to prevent it getting stuck.

When you have the two halves made up, drill 6 mm holes all over them on a 20 mm grid. (Read on)

Ready to fix the filler, mix some epoxy resin, and add some micro fibres and mix to about peanut past consistency, spread this all around the edge making sure all the old Balsa is covered, now spread some over the top of the filler and push the two sections into place, and press up, the holes in the sections will ensure ant trapped air can escape along with any extra resin mix.
Prop this into place and let it cure; make sure you have some cling wrap between the prop and underside of the prop. Take your time to get the best position it will save work later.

After curing, you need to grind an area around the bottom edges of the repaired section and the original cut out. This will provide a recess for fibreglassing the section back in. Just mix another batch of resin and micro fibres as above and again prop into position, tape up the holes only after each one has filled with the excess fibres.

All that remains is to glass up the recess and your done but for replacing the liner of painting.

Hope this helps.

Avagoodweekend......

 

[oldsaltoz]

The problem with injecting resin is that you can not be sure the core material is dry, also the area you are trying to stick together have had no preparation and may not stick.

This method will cause more problems if ANY moisture is trapped, the rot will continue spreading.

Avagoodweekend......

 

[boatmike]

The problem with injecting resin is that you can not be sure the core material is dry, also the area you are trying to stick together have had no preparation and may not stick.

This method will cause more problems if ANY moisture is trapped, the rot will continue spreading.

Avagoodweekend......

Your statement assumes the core is wet in the first place. In my experience the majority of sandwich deck failures are caused by excessive heat, especially if the boat has been used in the med or caribbean for any length of time. Also balsa is end grain and will not normally wick laterally unless already delaminated. Of course there are failures where the core is found to be wet, especially if fittings have been poorly fitted without sealing edges letting water in but unless proven to be wet injection is a perfectly adequate solution to many cases of dry delamination. I would agree where there are large areas of wet laminate the best solution is to remove the core and rebond and cosmetically this is simpler from inside but every case has to be judged on it's merits.