Boat Cracks on sides, how to repair?

[AleCiotti]

Hi guys during the years my boat has had some accidents and combined with the effect of time it now has a lot of cracks on it's sides, some of them are very deep.

How do I go about repairing the cracks, especially the deep ones?
Thanks!

see attachements.

 

[Tranona]

As ever there is no short cut. If it is sheathed (as it looks like in the photos where the wood is exposed), cut the sheathing back to reveal the extent of the damage, repair the wood and re-sheath. If the cracks are more superficial and just in the sheathing you may get away with just grinding clean and filling with an epoxy fairing filler. Painting needed afterwards of course, but it may be difficult to match the paint to make the repair invisible.

 

[Neeves]

Tranona is the expert on such things and maybe he will comment on my post.

Go to a section of the hull as far away from the damaged areas as possible and tap with a small hammer. That will be the sound of an undamaged part of the hull. Now tap the hull where the damage has occurred, that's the sound of a damaged part of your hull. It will sound very different if the sheath has detached from the underlying wood. Starting at the damaged portions tap and find the extent of the delamination of the sheath from the underlying wooden hull - which might indicate the areas of sheathing that have to be replaced or re-bonded. You can mark with chalk and then join up the dots.

Much will depend on the accidents, being 'T' boned by something quite large causes lots of damage. You can also check the interior for damage at the crack locations

Jonathan

 

[AleCiotti]

Thanks for the info, by "repair the wood" and "re-sheat" what do you mean?
My plan was: grind out the area of the damage and asses how deep it is, sand the surface, clean it, fill in with epoxy filler, and feather in the New Paint/Gelcoat.
Is it a correct way to go about it?

Thanks again,
Alessandro

 

[Neeves]

It appears you have a wooden hull to which has been attached fibreglass (a sheath). The fibreglass would have been adhered to the timber. Collisions may have damaged the adherence of the fibreglass to the hull. You should be able to judge this with the tap of a hammer. If the damage is extensive you will probably be unable to re-adhere the original fibreglass, the sheathing, to the wood which would necessitate cutting off the unadhered fibre glass and replacing with new.

In the absence of further evidence from you of the extend of damage I would suggest you use the simple hammer concept and then report back. If the damage is extensive you would be better to employ a surveyor and/or shipwright.

Your damage may be simply cosmetic and superficial - without more detail we don't know.

Jonathan

 

[AleCiotti]

It appears you have a wooden hull to which has been attached fibreglass (a sheath). The fibreglass would have been adhered to the timber. Collisions may have damaged the adherence of the fibreglass to the hull. You should be able to judge this with the tap of a hammer. If the damage is extensive you will probably be unable to re-adhere the original fibreglass, the sheathing, to the wood which would necessitate cutting off the unadhered fibre glass and replacing with new.

In the absence of further evidence from you of the extend of damage I would suggest you use the simple hammer concept and then report back. If the damage is extensive you would be better to employ a surveyor and/or shipwright.

Your damage may be simply cosmetic and superficial - without more detail we don't know.

Jonathan

Thanks Jonathan for your detailed answer,
The damage has a couple of years and it happened due to a shipyard wrongly lifting up the boat with a travel lift that ended up in the boat completely smashing on that specific point on it's side that caused a piece of the boat to fly off and the big hole to appear, the shipyard made a quick fix saying it was nothing to worry about and 3 years later the piece is coming off again, I will link below a photo of the damage right after the incident so you can have a better understanding of the dept, plus a photo of the repair as it stands today (coming off).
In this photo, you might be able to appreciate the layers that make the hull:

 

[Tranona]

It is coming off because their "quick fix" is not a permanent repair. You could do just the same again as you are suggesting on the deck edge and it is likely to last a similar time. More concerned about the damage to the hull lower down. Although the surface damage looks superficial you really do need to investigate further as to whether the sheathing is still attached to the hull. The simplest wat, as Neeves suggest is to tap around the area with a light hammer. Dull sound means potential failure of adhesion.

It is really important with repairs on this type of construction to cut back to sound wood, rebuild the wood then sheath in glass cloth and epoxy to fair into the surrounding area before painting to match.

 

[RunAgroundHard]

This is always my go too manual for GRP repairs. Have a search through, there may be something relevant. If not search their website as they provide solutions for all sorts of GRP and GRP laminate repairs.


Fibreglass Boat Maintenance | WEST SYSTEM Epoxy

 

[AleCiotti]

It is coming off because their "quick fix" is not a permanent repair. You could do just the same again as you are suggesting on the deck edge and it is likely to last a similar time. More concerned about the damage to the hull lower down. Although the surface damage looks superficial you really do need to investigate further as to whether the sheathing is still attached to the hull. The simplest wat, as Neeves suggest is to tap around the area with a light hammer. Dull sound means potential failure of adhesion.

It is really important with repairs on this type of construction to cut back to sound wood, rebuild the wood then sheath in glass cloth and epoxy to fair into the surrounding area before painting to match.

Will try to do the sound test while crossing my fingers as hard as I can , as for repairing the wood you mean cutting a small piece of marine plywood and attaching it with epoxy to the old wood to fill the hole? or just put a layer of filled epoxy on top of the wood?
I'm not sure if the sheating is made in Fibreglass though, I think it's epoxy, but in my ignorance, I can't confirm, do you see fibreglass in one of the photos above? should I sheat with glass cloth even tho old sheating is epoxy or something else?
Thanks!

 

[Tranona]

It might be just epoxy and painted, but it is common to apply a layer or glass cloth set in epoxy on modern wood construction. You really need to find out exactly how it was constructed before making repairs. The photo of the damaged rubbing strake (photo 5188) looks as it it is sheathed - the light surface at the edges is typical of what epoxy glass sheathing looks like, although it may be just a primer under the paint. I would guess the repair has failed because of poor adhesion of the filler to the wood. It probably needs the wood cutting back over a longer length then a new piece of wood scarphed in, glued and screwed so it is effectively part of the original and then coated in the same way as the original. Just filling wit epoxy filler is a short term fix.

Photos 3921 and 3928 are the ones that need investigation if the hull is sheathed as that sort of impact damage and cracking is an indication of failure of the bond. However if it is just painted then it is probably easier to repair by removing the paint to check for damage to the wood and recoating.

 

[AleCiotti]

Alright, well, i hope the sheathing isn't detached from the hull as that would be a big damage, I'm not able to do the hammer check straight away, will probably go to the boat in a week or so, I will try to check for the sound and see if it is actually that bad.
Meanwhile if it helps, the boat is a Starkel 56 named Khiva made in1999 and is made of wood and carbon composite, I don't know if maybe the year and the main materials might help in defining the sheathing technique that was used.
Thanks a lot for all the help provided, very much appreciated!

 

[Neeves]

To reduce your, possible, depression - collisions and delaminated hulls are not uncommon. If repaired properly the repairs are successful and the yacht has a long (and happy) life. You have what seems to be a botched repair - so you know what to avoid.

At this time my focus would be to determine the true extent of damage - how far does the delamination extend. Once you have identified the extent you can then devise remedial action. I maybe the damage is very localised - but you need to define.


The hammer 'trick' is a gentle tap, you don't need a big hammer (you don't need a hammer at all, you could use a screwdriver handle, but if you have small one - its ideal). Just tap, tap, tap and listen for the change in sound (and then mark) then repeat.

Jonathan

 

[William_H]

It is important OP gets to know the details of the sheath. If I remember rightly a product called dynell was promoted for sheathing. This cloth was easier to wrap in complex curves so preferred to glass. Since then we have kevlar which is similarly flexible but vastly stronger. of course the bigger the boat easier to use glass cloth. How thick is the sheath? A thin sheath is really just a thick paint job while a thick sheath can end up with a GRP boat on a wooden mold which remains.
Use epoxy for all repairs. regrdless of original resin used. It is best for attachment to the wood. Dry and warmb the wood before applying a thin epoxy coat that hopefully will soak in to wood. Then add more epoxy before it goes hard. I would think that epoxy with filler would be ok in lieu of replacing wood except in really large holes. Incidentally the tap test is called a coin tap test as a coin is all you need not a hammer. ol'will

 

[AleCiotti]

Will do the tap test as soon as I can, if the damage is boat wide with serious structural problems, I will then consult with the shipyard who made the damage and see how they want to proceed.
I'll also contact the shipyard how made the boat to ask for the hull materials composition and it's sheathing.
Thanks everyone for your help!

 

[Neeves]

Incidentally the tap test is called a coin tap test as a coin is all you need not a hammer. ol'will

We live and learn.

But coins are so 20th century

Jonathan

 

[Neeves]

Will do the tap test as soon as I can, if the damage is boat wide with serious structural problems, I will then consult with the shipyard who made the damage and see how they want to proceed.
I'll also contact the shipyard how made the boat to ask for the hull materials composition and it's sheathing.
Thanks everyone for your help!

This should be covered by the shipyard insurance but it might also be sensible to involve your insurer and have them on your side.

Jonathan

 

[Tranona]

Alright, well, i hope the sheathing isn't detached from the hull as that would be a big damage, I'm not able to do the hammer check straight away, will probably go to the boat in a week or so, I will try to check for the sound and see if it is actually that bad.
Meanwhile if it helps, the boat is a Starkel 56 named Khiva made in1999 and is made of wood and carbon composite, I don't know if maybe the year and the main materials might help in defining the sheathing technique that was used.
Thanks a lot for all the help provided, very much appreciated!

That construction method was state of the art at the time - in car terms the level of technology that was used in building supercars except that wood is used for stiffening the main panels of the hull and deck with glass and carbon used in areas of high stress such as rigging and keel loads or to reinforce against impact for example at the bow.

The basic structure is built over an upside down mould or framework which may include some structural framing commonly using cedar strip planking and then veneers of 3-4mm laid diagonally (or maybe all veneers) usually glued with epoxy. The finished hull is filled and faired then often sheathed with glass cloth and epoxy to seal the wood and provide abrasion resistance. This may well be vacuum bagged to ensure even adhesion, although that was relatively new when your boat was built. After further fairing the hull is painted - in your case probably very expensive paint to get that fabulous dark blue finish!

The advantage of this method is that it is economic for one off custom boats and the hull is lighter and stiffer than GRP at the time. Using carbon for reinforcement enables the designer more freedom in how he designs the load paths which often helps in designing the interior as bulkhead placement is less critical. It also gives a nice clean aesthetically pleasing interior finish to the hull, particularly if that is also sheathed before adding the interior.

Unsurprisingly few boats are built like this as the owner has to be rich to afford it and it has rather fallen out of favour being replaced by composites that use more vacuum moulding and foams as stiffening rather than wood. It is however still used in really high class wooden boat construction such as Spirit Yachts spirityachts.com

The big enemies of this method of construction in use are impacts where the damage can be far more extensive than appears on the surface and water ingress, particularly freshwater around the above the waterline junctions. Hull to deck, coachroof to deck and any fittings attached to the deck where cracks can allow water into the wood core. Teak decks are particularly problematic depending on how they are attached to the deck. Bilge areas also need regular inspection as any fluid there can potentially get into the core.

You really need to find out exactly who built the boat and how it was built. My description above is necessarily generic and individual designers and yards will develop their own variations. I can't find anything on line about the builder and the designer unfortunately died recently, but a number of similar designs of his were built in a similar way so so doubt in Italy there is somebody or yard that knows about the boats.

 

[AleCiotti]

Hi Tranona,
Thank you very much for the extensive message and the tips, I am indeed in contact with the owner of the shipyard who built the boat as he still owns that shipyard and still builds!
So that said I will contact him and have a chat about what we discussed in this thread.
Thanks, everyone for your help, I will keep you updated on how this goes!