srm
Well-Known Member
Why do you think they need internal support. Is the fibreglass around the hull / keel joint area showing cracks or flexing?
GRP Lysander restoration
- Thread starter nigelclough51
- Start date
DownWest
Well-Known Member
I was wondering that, since they are short, the leverage is not great.
a) Are they splayed, or vertical?
b) Moulded with the hull or fastened on afterwards?
If a, then likely mouldedwith the hull and no extra internal bracing.
And, what do you have in the hull now? One is assuming a restoration, not a hull that was never finished.
Tranona
Well-Known Member
If they are bolted on there will be similar reinforcing framework, either extra layup or moulded in stringers. You would also of course see the heads of the bolts although they may be glassed over and just look like lumps. If they are part of the moulding then there won't be any specific "support" but the layup will be such as to carry the load of the ballast. Normally the ballast would be bonded in and glassed over so the area where the keels are would look like the rest of the bilge area of the hull.
nigelclough51
Member
It's belt and braces really if we beach the Lysander on rock etc.
I've been advised to put in 3 fibreglass enclosed top hats each side, what ever they are?
More research!
Best regards Nigel and Paula.
Tranona
Well-Known Member
Think one would want to avoid beaching on rocks. You say 3 top hats - does that mean it is triple keel - longer central keel and 2 bilge keels? If that is the case I expect you will fine that the central keel is deeper than the bilge keels so she will settle leaning to one side. I think the top hats refers to adding sacrificial shoes to the bottom of the keels. One of the big downsides of moulded in keels, particularly bilge keels is that if you ground regularly for example on a drying mooring with a stony bottom the GRP can wear away and water gets in leading to rusting of the ballast. In extreme cases if left the rust expands and ruptures the moulding. The shoes reduce the likelihood of this. Otherwise I think you will find the hull is overbuilt and quite capable of taking the ground.
DownWest
Well-Known Member
I suspect the 'tophats' would be transverse stiffeners formed by laying glass over paper rope or foam square section to form 'girders'.
srm
Well-Known Member
If wanting protection for the bottom of the keels I would suggest the system I had on my Prout catamaran. Simply a hard wood strip about 50mm thick bonded to the bottom of the keel with Sikoflex or similar and shaped to blend in with the keel. The wood should then protect the grp and ballast in the event of a grounding. If unsure about the bond a glass and epoxy tape could be run over the sides of the wood and onto the sides of the grp keel.
Definitely required if the area around the roots of the keels and surrounding hull show any stress cracks in the gel coat. Otherwise, probably not needed as early grp lay ups were usually over engineered.
Just a general point regarding your restoration. It is a natural temptation to overbuild everything, but each gram of material you add increases the weight and displacement of your boat, conversely reducing the freeboard. My current boat was home completed from the grp mouldings by the previous owner who beefed up and added a number of features. Before launching I cleaned off all the old antifoul and epoxy barrier coat before applying a high build epoxy and Coppercoat. I found the design waterline scribed on the hull and a filled in exhaust outlet well below the actual waterline. I assume the exhaust outlet had originally been fitted in the designed position, only for this to be totally submerged when the boat was first launched.
nigelclough51
Member
Hi I've tried to load up some photos to show what we have, however the forum tells me that they are to big to process!
So more tec playtime tommrow.
What I can tell you is that the keels are encapsulated in fibreglass, moulded with the hull and both toed in at what appears to be the same angle.
Best regards Nigel and Paula.
DownWest
Well-Known Member
Same prob, but this: Compress images online - Reduce your image size online and for free might help.
From what you have posted, it sounds like the bilge keels are probably not a problem. Your terminology in the ' keels are encapsulated in fiberglass' might be a bit off.
The keels 'are' the GRP mouldings, apparently with the hull, so, unless you have some info that they are weak... Best get on with the rest of the restoration.
From what you have posted, it sounds like the bilge keels are probably not a problem. Your terminology in the ' keels are encapsulated in fiberglass' might be a bit off.
The keels 'are' the GRP mouldings, apparently with the hull, so, unless you have some info that they are weak... Best get on with the rest of the restoration.
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nigelclough51
Member
srm
Well-Known Member
Looking at the pics I suggest that you clean off all the old antifouling etc. and get back to the gel coat. Note that some of the earlier grp hulls were laid up with clear gel coat below the waterline.
When you are back to the gel coat it will be easier to assess the state of the keel / hull area and decide if you need additional support inside the hull. You will also be able to see the state of the rest of the gel coat and make good any damage. Any cracks or damage must be made good as the gel coat is the (semi) waterproof membrane for the hull.
Having cleaned the hull, and with the hull dry after being ashore for the renovation it would be advisable to apply an epoxy coating below the waterline before antifouling as this gives a second (almost) waterproof membrane to protect the grp lay up..
Note: cleaning the hull back to the gel coat is a most unpleasant job and the old antifouling will have residual poison in it. I did it on my previous catamaran. With my current boat I paid to have it soda blasted and only had to use an orbital sander to remove the remaining base coat.
When you are back to the gel coat it will be easier to assess the state of the keel / hull area and decide if you need additional support inside the hull. You will also be able to see the state of the rest of the gel coat and make good any damage. Any cracks or damage must be made good as the gel coat is the (semi) waterproof membrane for the hull.
Having cleaned the hull, and with the hull dry after being ashore for the renovation it would be advisable to apply an epoxy coating below the waterline before antifouling as this gives a second (almost) waterproof membrane to protect the grp lay up..
Note: cleaning the hull back to the gel coat is a most unpleasant job and the old antifouling will have residual poison in it. I did it on my previous catamaran. With my current boat I paid to have it soda blasted and only had to use an orbital sander to remove the remaining base coat.
nigelclough51
Member
Thanks for all that and hull soda blasted definitely a good idea.
Best regards N&P.
