Building Fiberglass Boats

[wcnfl]

I have a few questions on building fiberglass boats.

1. How do you know if your design works before you invest in building a plug and a mold?

2. Do you build a cold mold plywood boat to test?

3. How do production boat companies know a design works before producing?

Originally Posted by wcnfl

I have a few questions on building fiberglass boats.

1. How do you know if your design works before you invest in building a plug and a mold?

Experience with similar boats, tank testing, sometimes wild guesses.

2. Do you build a cold mold plywood boat to test?

No, that would mean building a "better" boat as a test run, than the final product.

3. How do production boat companies know a design works before producing?

Not.

Hope you do´nt mind that I replied in your post!

Regards
Richard

[wcnfl]

Do boatbuilders consider a plywood cold mold better than a fiberglass hull?

Of course!



......and I do both!

[PAR]

If you have a need for an answer for question one, you have the wrong staff, the wrong designer or both. A custom design should have sorted out your apprehension long ago, other wise the designer isn't doing their job.

If you have performance questions, you can do a number of tests, ranging from simple software analyses to costly tank tests. Unless you're hull shape is well out of the usually realm of design paths, reasonable performance predictions can be assumed. Again, you can trust the designer or insist on (read pay for) more testing.

Building a prototype (#2) is often employed if, you've ventured out on a limb with the design elements. A cold molded build is no better of worse then any other test bed for prototype. Of course some folks prefer certain materials and build methods, but in reality, most modern wooden construction is more closely related to 'glass then wood.

Again, you seem to be asking the same question (#3), just differently. Typically, those involved in a venture like this have a fair idea of how boats should be shaped. If your boat seem to fit within normal proportions, weights and power requirements, then you can be reasonable confident.

On the other hand if the design is out in left field, you have only two choices, test it further or trust the designer.

[wcnfl]

Thank you for your response...

[tunnels]

Originally Posted by wcnfl

I have a few questions on building fiberglass boats.

1. How do you know if your design works before you invest in building a plug and a mold?

2. Do you build a cold mold plywood boat to test?

3. How do production boat companies know a design works before producing?

Best to build a wooden boat first and the try it out if it works fine then build a boat over the top of the existing wooden boat !.
Why do you want to build a mould???
are you intending to build 10 or 100 boats or more ??

Originally Posted by tunnels

Best to build a wooden boat first and the try it out if it works fine then build a boat over the top of the existing wooden boat !.
Why do you want to build a mould???
are you intending to build 10 or 100 boats or more ??

No professional does so.
As PAR already said, we build to proven and well known designs, and / or well known designers. There is little chance to get a faulty design.
When large series are planned, almost always some tank testing is made to tweak the design.
But it is not common and not necessary to build a full size "test boat" prior to production.
We even set up our moulds for a 43 meter semicustom straight from the drawings.

Regards
Richard

[tunnels]

I dont think a individual has the backing for what you are talking about ! I have work making boat for 25 years from 10 foot to 174foot and the process is not the same .I also work in many differant countries for many differant companies so be it a yacht or a power boat ,tank testing is not for the man on the street to just take his modle and get tested .
Dont know why im even bothering answer this !!

Originally Posted by tunnels

I dont think a individual has the backing for what you are talking about ! I have work making boat for 25 years from 10 foot to 174foot and the process is not the same .I also work in many differant countries for many differant companies so be it a yacht or a power boat ,tank testing is not for the man on the street to just take his modle and get tested .
Dont know why im even bothering answer this !!

Do´nt know either!

But would help to read a thread before you contradict! Maybe at least you would understand us.

Are you a bit in a "bad mood" today?

[PAR]

We shouldn't second guess the original poster. It's clear he has reservations about a specific design. We don't really know what's going on, so everything else is speculation. He may be having a custom 'glass boat built and thinks it will come out of a mold. He may actually be setting up for a production run, at which point I'd suggest he needs a better staff, to keep him informed.

[Angélique]

Originally Posted by tunnels

Best to build a wooden boat first and the try it out if it works fine then build a boat over the top of the existing wooden boat !.
Why do you want to build a mould???
are you intending to build 10 or 100 boats or more ??

Stuart Brown of Churchouse Boats about the Paul Fisher, of Selway-Fisher, designed Drascombe Drifter 22 in Water Craft may 2005 page 56:

‘‘ The prototype wood-epoxy hull is currently being fitted out in our yard; the objective is to create a GRP production boat. To this end, my wood epoxy boat is being built as a sailing plug. This is not the normal way to create a GRP boat but I’m not a normal boatbuilder; in the constuction industry, every project is a one-off. To build a wooden boat but also use it as a mould creates its own disciplines: all surfaces must be sloped to allow release from a mould; all radii must be large as per GRP requirements, not softened as in a traditional wooden boat. All internal corners must be radiussed. The easy option of MDF and filler is not open to us. The grey matter is being taxed! ’’



From Churchouse Boat's website about the Drascombe Drifter 22:

‘‘ Although our prototype was in wood epoxy, all the production boats are GRP. ’’



Magazine articles about the prototype (plug) sailing:

- Water Craft, august 2006 page 13 - 16.

- Sailing Today, october 2006 page 112 - 114.

- Zeilen, october 2008 page 78 - 84 (Dutch).



Regards,

Angel

[tunnels]

Building moulds is costly and very wastful , how many moulds do you find in boat yards that have had there day so to speak ? lots !!
By building a proper wooden boat and then building a proper firbreglass boat over the top of that wooden boat its possible to have just the steel skeleton frame and stands that end up as scrap metal .
we have done this on numerous occassions where a limited number of fibreglass boats were to be made from the mould . when the last boat was demoulded then the glass mould (which was a boat ) was totally sand blasted and ground inside , had the steel frame removed sat into a wooden cradle to hold the shell firm and steady after fairing ,sanded and painted the outside , it them became a proper boat , Its not exactly the same as the glass boats but got sold as a specal one off and so the cost were recovered totally and no mould hanging around the grave yard of old unused moulds .to develop a set of moulds for any boat is a cost that it in 99% of cases unrecoverable and has to be built into the cost of X number of boats . Plus you have a plug that has to be sent to the tip , so much waste !!!!!

[gonzo]

I've surveyed several molds sold as boats. They are full of structural and other problems. Also, they are very heavy. Only dishonest builders would get involved in something like that.

[Angélique]

Originally Posted by gonzo

I've surveyed several molds sold as boats. They are full of structural and other problems. Also, they are very heavy. Only dishonest builders would get involved in something like that.

‘‘ .... we have decided to offer the strip plank storm 17 hull (that we used to make the GRP mould from) .... ’’

‘‘ .... made of wood in such a way that moulds could be made from her for the production GRP boats. She was sold .... ’’

Well, invite them to this forum.........

Regards,

Angel