Epoxy,mahogany core construction.

[bg9208]

Found a nice boat at about the right price but not familiar with this epoxy, mahogany core method of construction, where does it stand problem wise, towards the solid fibreglass end or the home built ferro/cement end? If there are problems specific to this type of cinstruction, what might they be?

 

[oldsaltoz]

G'day bg9208,

Strong and light, good thermal and sound insulation so better GRP in some respects.

The better ones are solid glass below the waterline, make sure you check the hull moisture below the water line before commit. Or better keep looking till you find one that is solid glass below the waterline, we did.

Some Catamarans were not built as strong as they could have been in the bridge area causing some sag between the hulls, so have a good look from head on in particular.

Also check all thru deck fittings, hatches in particular and the deck underside of the anchor locker to make sure the timber has been properly sealed.

tapping a coin will detect any de lamination of the skin, but this highly unlikely.

Our cat is strip red cedar and solid glass below the waterline, never had a problem, it's a production boat built in the USA and sailed to Australia.

There are plenty of this type well over 20 years old and going very strong.

Hope this helps.

 

[Tranona]

Depends on exactly how it is constructed. The core could either be strip plank or multiple layers of veneer. Some are built over permanent frames and maybe sheathed on the outside with glass cloth set in epoxy. Others are built over moulds and sheathed inside and out, with frames and bulkheads bonded in afterwards.

The main things to look for are any potential points of failure of the epoxy skin that allows water to get into the core. Decks and superstructures can also have weak points allowing water in. Repairs can be difficult and expensive.

On the positive side if the boat is well built to a good design they are often very attractively finished, exploiting the wood down below.

You will get good information on epoxy techniques on the www.wessexresins.com - the distributor for West resins. West also publish a comprehensive book on boatbuilding.

Hope this helps

 

[johnlilley]

As others say, it depends entirely on original method of construction. Mahogany core and epoxy, suggests to me strip plank that has been epoxy coated subsequently. Boats built before about 1985 are often strip plank then sheathed. The weak areas of these are glue failure of the planks if not epoxy glue, most pre 1970's will not be epoxy. This then turns reliance on the edge fastenings which are sometimes ferrous nails through the edge of the planks. Obvious corrosion problems when seawater gets to these.
Many early strip plank boats have had problems keeping them structurally sound by now.
Later all epoxy saturation build have few fastenings and provided the epoxy coating is total and sound do have the potential for long life as the method of construction is very different. Mcmillan were builders of some very specialist epoxy saturation build yachts for a few years in the late 1980's. The Prior 30, Cheverton Caravel and some others conventional strip plank edge fastenings.

Might help a bit

John Lilley

 

[William_H]

The description could be a saleman's hype. It could vary between an ordinary wooden boat with an epoxy layer on the outside through to a well built epoxy boat with wooden core.

I would look at it with some supicion. Certainly a polyester resin boat with solid fibreglass will last for ever compared to a wooden boat.

Yes many will disagree so get more advice on this specific boat. If you buy a well known and respected boat type it will maintain a much better retail value. good luck olewill

 

[Tranona]

Should perhaps have added that very few "production" boats use this method because it is more expensive than GRP. So tends to be used for one off or custom building, both professional and DIY. Therefore the design of the boat is important. Many "odd" boats have been built using custom techniques because the owner could not get what s/he wanted in a stock boat. Low secondhand prices can also reflect the design as much as the method of construction. A good pedigree from a well known designer is therefore important.

 

[rwoofer]

I have a modern epoxy/plywood boat and would actually consider it superior to GRP/ balsa core in terms longevity.

It feels like the majority of modern production boats use Balsa in the deck and quite a few use balsa in the topsides. If you look at something like the new Jeanneau Sunfast 3200, the topsides balsa is fully visible through the see-through glass in the lockers. My own boat is actually made by RM yachts and although the hull is epoxy/plywood, the deck is actually GRP/ Divinicell. This was a deliberate decision by a builder that understands wood to avoid balsa altogether.

The point is that of all the woods you could mention balsa is one of the least resistant to saltwater (it turns to a horrible mush), yet is used in a significant number of production boats. On the other hand, mahogany is one of the more resistant to saltwater, so assuming it has been built well I would be less worried than some of these so called GRP boats.