Recommissioning of an old hull mould

[Makloko]

Bajansailor, the boat in the backside is a 5.5m, not coming from this 8m70 mold.
I have a final design, I'll try to post some pictures soon

 

[gonzo]

Making a new mold takes more material than building a hull. That hull design is quite obsolete. Have you done a market research of who would buy them? Also, the owner of the design, if there is one, may want royalties.

 

[ondarvr]

It will take about 184 kg of materials to cover that surface area with each 3mm of glass. The minimum amount of material to use 3mm coremat would total about 9mm or so. Which means it would be in the range of 552 kg of materials. The resin to fabric ratio would be around 30% fabric to 70% resin. Coremat soaks up a lot of resin, so that ratio could vary a bit.

Figure on 386kg of resin and 165kg of fabric. Fabric includes both CSM and Coremat.

A hull will take far more than that, maybe 6-7 times more, and the fabric used will cost more. Thats just the hull alone, it doesn’t include any core, stringers, bulkheads or anything else, so add in whatever structure you plan to build on the hull.

These are just rough estimates, I didn't spend much time on it.

A hull mold will take about that same amount of materials as building a hull, plus other supports and framing, and gel coat is very expensive.

So if you're on a tight budget can you afford the cost of those materials and several years of time to build and finish it?

 

[wet feet]

Regardless of the financial position,I would be more concerned about the need to wait a while before doing any work to the mould.The temptation to use a pressure washer can lead to later issues as the deteriorated laminate will have absorbed an amount of the water that was used to remove the old surface contamination.Water on exposed fibres would have soaked in a little but applying it at several dozen times atmospheric pressure will have driven it into the fibres and it will take a while to come back out in ideal conditions.Outside in a European autumn is some way from ideal conditions.I like to see restraint used with pressure washers as it can be too easy to pull the trigger and do damage;one common situation is blowing the vinyl boat name clean off the hull.

I would question the need for a great deal of extra reinforcement in any case as there may be no need to alter what has already been shown to work,as the mould has produced a number of apparently satisfactory hulls.I know a little about hull moulds that swing on end supports and they don't have to receive the loads of a laminating team walking around inside.What can be used is a wheeled working platform that moves along the job as work progresses.The mould only really needs to be upright and level when the stringer grid and bulkheads are located and it may be a good idea to position a couple of keel support blocks at this stage.One challenge that can come from a lightweight mould is actually releasing the hull.Bonded lifting points can allow an overhead hoist to lift the hull plus mould into the air,which is when people wander along with rubber hammers, walloping the surface and causing star crazing.Earlier posts suggest that this has already happened.

 

[ondarvr]

I'm not sure I would worry about water absorption from pressure washing. That surface has had moss and gunk growing on it for very long time, that laminate is about as saturated as you can get it at this point.

Removing all that stuff is the primary concern so he can determine what the next step is, then grinding it to achieve a good bond if he plans to put additional material on the outside.

To put a laminate on the outside it will need to be indoors in a somewhat climate controlled space, which will dry out at least the surface so it will stick. And it will take a significant amount of time before any lamination would start, so it will continue to dry out. Moisture left deeper in the laminate isn't good, but isn't going to cause any problems at this point, and since it's already there, he can't do much more about it.

And this is only a concern if he decides to add more material, it may need nothing, but he won't know until the surface is thoroughly cleaned.

 

[comfisherman]

Ive ressurected a big flybridge venturi mold and a cabin mold that had a few eggshell cracks. It was caused by wet core freezing and thawing making the eggshell spiderweb Crack in the tooling gel coat. We cut out the bad core and slapped in some plywood and combi matt over it. On the inside we ground out the eggshell cracks and faired and filled it. Then put on new tooling gel and buffed it along with the rest of the mold. It didnt fix it perfectly and some imperfection was passed on to the part.

Not sure how it would have held up long term, we pulled one part and then chopped up the mold as we had nowhere to store it or any long term use of it.