Transom crack repair

BruceB · 07 July 2013, 19:05

After a lay off and leaving the RIB under cover all for nearly a year while I moved job, house, job and house again I started sorting out Wavesweeper to get it ready to use again.
Its spent a year unused under its cover in the drive and its time to get her out again.
filled some mnor hull scratches, checked out all the elctrical systems, started the motor, rebuilt the brakes and replaced all the bearings as well as a general tidy up of the trailer.
All fine, ready to go and working. Then the reason why I have no confidence in Humber construction quality reared its ugly head, I noticed a crack along the top of the transom, again!
Severly p**ssed off because this is the third time the transom has cracked I took the grinder and ground down the crack to see what and how bad it was. on going through the gelcoat and about an inch of glass I reached the top of the ply. The crack is about 3-4 inches long and about 1/2-3/4 inch deep but doesn't seem to reach the ply.
So its not too bad and now just needs repaired.
What do I need to reglass the transom and repair, bearing in mind fastglass is the only material I have ever used. What do I need to do and what materials do I need and should there not be mat over the top of the ply?
Any advie appreciated, pics will be posted later of before and after.

ShinyShoe · 07 July 2013, 19:16

Needs a picture.

What is on top of the ply? You say there is no mat but also say you went through an inch of glass?

frankc · 07 July 2013, 21:08

Always use mat under cloth against plywood. Make sure there are no air bubbles in the layup.

Glass delaminating from plywood is a common problem unless epoxy is used and is not 100% even then unless the wood is properly roughed up and saturated.

Sounds like your transom is flexing under load.

BruceB · 07 July 2013, 21:18

Patience! I had to download the pics.

Before shows the crack. after once I had taken a grinder to it and exposed the solid construction underneath.
The crack only seems to be in the gel coat and glass over the top of the transom. However there is only glass and no mat over the wood, is this right?

The question now is what do I need and how do I glass it back and re-gelcoat

ShinyShoe · 07 July 2013, 21:28

So is that just resin? Or resin with chopped strands? If its resin then resin has no strength without fibres. So the bit you replace will be stronger than the surrounding resin and so will crack loose?

Does that A Frame get used to transfer a load? Ski? Used to tie up to a jetty etc?

BruceB · 07 July 2013, 22:04

The A frame is sometimes used when coming alongside for mooring but you can discount this as a cause, you can't see the rest of it and all the other mounts. Its a big double frame 2" jobbie with deck mounts and was origionally fitted by Humber (although I then had to remove, weld and refit it cos it was fitted squint and had one leg longer than the other!)
Theres a bit of history here in that the other side of the transom cracked twice and was repaired by Humber twice with no good cause other than shoddy contruction and repair.
There doesn't seem to be anything there bar glass, hence the query on what the best way and materials to repair are.
How do I reglass this crack I have ground out and what with?

biffer · 08 July 2013, 06:49

You will have to strip the top off and put a few layers of glass matting on that to stop it doing it again. This is the old story of why some boats are dearer than others

ShinyShoe · 08 July 2013, 08:23

So if its just resin (resin is not glass - the fibres in GRP are the glass bit!) you need to remove the resin back to something stronger - somethign with fibres - wood or CSM. Then replace the chopped out bits with something with fibres in it, ideally going from back to front not just a strip on the top.

Wondering if fibreglass tape would be an easy way to do the job?

Dirk Diggler · 08 July 2013, 08:39

Quote:

Originally Posted by biffer

This is the old story of why some boats are dearer than others

frankc · 08 July 2013, 09:23

The proper repair would have to wrap over the transom. Once you ground off the top of the transom, the repair became a structural one. You may have been able to fill the crack with epoxy before grinding, but once the top was ground away, a proper repair is necessary.

The front and back of the transom would need to be ground away at a 3 to 6 inch or more taper and a mixture of mat and fiberglass cloth applied. That would then need to be ground flush with the surfaces of the transom and then finished.

The mat serves as a filler for the weave of the cloth and helps bind the materials together. It is a necessary component of proper bonding of the patch. The real strength of the layup is in the fibers of the glass cloth. The random direction of the fibers in mat do not add much strength to the layup.

It is important what resin is used in the layup and how much. It is doubtful that the boat is made with epoxy resin, but that would afford a stronger layup. It can be used over poly resins but poly resin cannot be used over epoxy.

If you try to just replace the ground away portion with a patch, it will have no strength and the small split which you saw before will be minor to the situation you will have on your hands. In other words, you cannot edge glue a patch on top of the transom and expect it to hold.

Unless you have worked with fiberglass before, you are probably in over your head and must pay an experienced person to effect the repair.

Refinishing will also be a challenge, as it will be difficult to match the existing transom finish. You may have to paint the complete transom, as applying gel coat for the unfamiliar craftsman is a very difficult job. I have done several repair jobs on fiberglass and would not attempt to do a gel coat job.

Pedrode · 08 July 2013, 09:33

I have a crack in exactly the same place on my Attaque. I filled it with epoxy to stop water ingress and have monitored for further or new cracking and it's been fine. Decided that minor surgery is preferable to major and as long as water isn't getting to the ply then structurally it's fine.

macattack101 · 08 July 2013, 11:17

I have a similar problem and I have no clue about repairing fibreglass so looking for a professional in the central belt of Scotland. Does anyone have a recommendation?

frankc · 08 July 2013, 13:01

It is a shame, but many boats suffer from cracks in the transom. They can vary from superficial to places where water intrusion can occur. If water intrusion occurs, the plywood can rot and ruin the transom.

You want to watch for this condition and attempt to seal the crack as soon as you can. If it can be sealed and does not get worse, you should be okay. If it begins to cause rot, there is a product named "Git Rot" which can be injected to solidify the wood in the area. I believe it is just thin epoxy capable of saturating the wood and waterproofing it.

Her is a link you might want to look at:

BoatLIFE | How to use "Git"-Rot