GRP Hull Project Help?

[David Cowen]

Hi,
I am embarking on a personal lifetime ambition to build my own fishing boat. I have bought a 28ft GRP hull in need of replacement ribs etc. I was wondering if anyone, who has a project past or present that they have documented on the net, could post up the link so that I can get a feel for the various consruction techniques. I have seen a GRP hull being made from the mold but my hull has lay open to the elements and needs the timber replaced where the previous owners have made nail/screw holes and allowed water to get into the underlying wood. The hull has been painted with a two pack paint and I think I will repaint using the same as I have seen some pretty good finishes. Can anyone help? Thanks.

[Dutch Peter]

Originally Posted by David Cowen

Hi,
I am embarking on a personal lifetime ambition to build my own fishing boat. I have bought a 28ft GRP hull in need of replacement ribs etc. I was wondering if anyone, who has a project past or present that they have documented on the net, could post up the link so that I can get a feel for the various consruction techniques. I have seen a GRP hull being made from the mold but my hull has lay open to the elements and needs the timber replaced where the previous owners have made nail/screw holes and allowed water to get into the underlying wood. The hull has been painted with a two pack paint and I think I will repaint using the same as I have seen some pretty good finishes. Can anyone help? Thanks.

David,

You haven't had many replies, what is it that you need?
You have a grp hull, but apparently with a wood core (so, sandwich construction)?
You want to know about construction techniques or about repair techniques?

Post some pictures of your boat so we can see what the problem is.


Dutch Peter

[David Cowen]

I have a grp hull that has been poorly looked after. It looks to me as though it has been pulled from the mould, finished with the basic supports ie ribs and stringers and then had a very ad hock fit out to get it on the water. I once saw a charter vessel being built from scratch using a similar hull to mine in Boat Angler Magazine here in the uk but that was quite some time ago. I wondered if anyone had undertaken their own build and documented it on the net so that I could check it out for ideas on building a cabin, replacing ribs and stringers that have been water damaged etc. I have bought the Fiberglass Boat Repair Manual by Allan H Vaitses. I have found this very helpfull but I like to get ideas from many sources because I have seen some very good ideas implemented by other users on various repairs etc. I will also need to decide on propulsion now as well so that I can get the correct engine bed set up. I have visited all the poular boat building sites here in the uk dedicated to Private Fishing vessels, which is what I want to use it for and again have seen more ideas but the more the better as far as I am concerned. The hull is not sandwich construction. It is single skin with ribs etc laminated in after being pulled. I am going to post some pictures my self on some webspace I have. It's best to see rather than try to describe!

[Dutch Peter]

So the water ingress is in the ribs, but you're gone replace those. Wood again or foam?
If you take out the ribs make sure the boats is layed up properly, so it will retain it's shape! Or remove and replace ribs one or two at the time.
Engine bed: structural foam with steel plate laminated in on top or just solid hardwood. Make the bed twice as long ant twice as wide as the engine, to spread the load.
I don't have a GRP-boat, I have a wooden desaster, comes with it's own problems.
I wish you good luck.

[David Cowen]

The ribs etc are wood but foam is tempting due to its easy workabilty for shape etc. The bed is hardwood but again foam with plate sounds good! I am trying to get the best way to make all the ribs etc water tight so that I don't have to worry about any water ingress at least as long as I willl have it. I am also thinking if putting down a marine play deck and glasing it in but I am unsure about the underside of th deck i.e how should I treat it before I glass it in so that rot won't come in from the underside. I am planning watertight bulkheads at say ever 4 feet and and ribs at every 2 feet. I plan to run a stringer the length of the boat to give the deck support at the sides and to give me something to glass to. The hull has very little keel so I am cosidering adding one due to the fact I will be building on a cabin etc. To give the dimensions the hull is 28ft loa with a beam of 11ft at its widest point which is roughly 10ft from the bow. From floor to gunwhale is roughly 4ft. I'm not familiar with a lot of the jargon relating to boats other than the basics! I have been party to building a grp hull from the mould before so I familiar with the basic techniques but practices have moved on I'm sure since a last did it abot 25 years ago ish!

[Dutch Peter]

What your saying makes sence, accept for the watertight bulkheads every 4 ft.
I think it's overdone! If you want one make a collision bulkhead, at 5-8% of the lenght aft of the bow (typical classification rule). This will give you a locker to store your ground tackle.
Stringer for the deck sounds good, marine ply for the deck give it a coat of epoxy and you've preserved enough!
If you're adding a keel, think of heavy floors and probably side girders to distribute loads. Look at other boats and how their bottom structure is laid out.
And posting here will eventually give reactions, weather you like 'm or not!

[David Cowen]

Thanks for that! Epoxy seems to be mentioned a lot here. I must admit I have not seen a lot of it advertised here in the UK. Is there a well know supplier who would have an outlet over here or is there a poular brand used worldwide? I plan to use Polyester resin to keep costs down and I have heard there may be some difficulty getting it to adhere to epoxy. I suspect the the hull will be made from polyester since it seems to be used a lot in boats over here. The bulkhead idea was to support the floor across the beam and I had planned to have the floor around 2 feet high to install diesel tanks, engine well etc similar to how the offshore 105 is laid out. I believe there are pictures at www.offshore105.com No this isn't a plug for the company but one of the few that show you construction techniques. I much appreciate input from anyone and I don't mind criticism if it saves me time and money!!

[Dutch Peter]

Originally Posted by David Cowen

The bulkhead idea was to support the floor across the beam and I had planned to have the floor around 2 feet high to install diesel tanks,

Sorry David,

Just so we don't get confused, in shipbuilding a "floor" is what your calling a bulkhead, and the "sole" (from: PAR - hard chine def, thread) is what you call the floor. To complicate things even more, I believe the sole is composed of floor boards.
But, then you're previous story does make sence!
Epoxy is mentioned a lot because it is better to use when repairing polyester! It's bonding much better! But, yes, it's more expensive.
ou can however decide to use polyester on the parts you're building new and bond them to the excisting parts with epoxy, that will reduce the amount of expensice stuff you need.

Suppliers: as at local boatbuilders or look at the websites of the different brands, West systems, SP, enybody know more????

The layout of the offshore 105 looks fine, and now I understand why you use the word bulkhead, never mind.
Use the search option (if you didn't already) and you'll find lots of info about repair, epoxy, etc. etc.

Hope this helps.

[sorenfdk]

In the UK, you can buy epoxy from Wessex Resins. Sorry, but I don't know their URL.

[Dutch Peter]

Try getting a free subscriction of "Professional Boat Builders", lots of info that can be of help!

[David Cowen]

Thanx guys for all the info.

[JR-Shine]

Check out www.classicmako.com

They have a lot of great rebuild pictures.

Joel
Boatbuildercentral.com

[David Cowen]

Thanks for that link JR. Some very good stuff in there.