Encapsulated Bilge Keel moulded to the hull stress cracks. Keel Strengthen project.

[MartinCB]

Newbie to GRP requires advice on strengthening the keels on a Hurley Silhouette mk 3. The keels are moulded with the hull so no bolts.

What i am unsure about is how far I should apply fibreglass above and below the hull to keel join vertically to add strength, how many layers i should apply and the best way to wrap the layers around the hull to keel join horizontally. Should I layer with one cut piece all the way around the keel join horizontally or use several pieces. Do I need to overlap the layer ends or line the layer ends up at different places in each layer? Best to overlap or have vertical joins?

Also should i cut the layer lengths with increasing or decreasing widths feathering the fiberglass or cut them the same?

Should I grind just to the white GRP hull or a little deeper to where I can see the fibres in the fibreglass for the new fibreglass to be attached?

I would be grateful for any advice to help me on my first project.

 

[oops!]

Re: Encapsulated Bilge Keel moulded to the hull stress cracks. Keel Strengthen projec

hi.....welcome to iboats !

what is grp?.....do you mean frp?

do you mean glass reinforced plastic?......or fibreglass reinforced plastic.......this is known as FRP.

if so.......are we working on a sail boat?......(blow boat)

or if not.....why are you worried about the keel?

im just trying to understand your post......repairing FRP's is easy....

click the link in my sig it has the best glassing information of the net.....many top pros in the nation commented on how to glass.

the basics are........grind the glass so you get to fibre.....it the fibre is white.....it cannot accept resin any more an you need to get rid of the bad glass. just grind deeper.

lay your first layer of Chopped Strand Matt (csm) the size of the area.....the next layer of 1708 is the same size. the next layer of csm and 1708 is larger than the first so that you are bonding the edge of the overlap to the hull........then repete. (basically start small and work bigger.) each layer of 1708 or woven cloth, MUST have csm between the sub-straight. or even another layer of woven or 1708.
resin is brittle, and you MUST use csm to be a interface between the stronger, thicker woven or weave material. this will give you a correct bond between the sub straight and glass to glass.

remember......use your resin roller to get rid of air.......and allways use wax (airdry) in the final layer that is exposed to the environment.


if the hull has a hole.....then it is an inside out side repair......meaning the glass must be repaired from the inside of the boat .....and again on the out side.

but start a thread in the restoration section......post pics, and lets see what you are working on......each repair is different.

but have no fear......you can do it.

 

[MartinCB]

Re: Encapsulated Bilge Keel moulded to the hull stress cracks. Keel Strengthen projec

Thankyou for your reply.

I understood that GRP was fibreglass and was unaware of any difference as in GRP or FRP.

Yes the boat is a sail boat that can dry dock on both keels. This is why i want to strengthen them.

Some water is coming in from the top of the keels and was starting to increase So i guessed that it was because of creeping cracks where the keel flexes with the load of the boat. I have grinded a little and have revealed some cracks. I did attempt digging out the cracks i found and filling with epoxy putty but this didn't work as when the weight was lifted off the keels when the tide came in it pulled the putty off the hull (since i did better research). The boat is now out of the water.

When i have time i will fill the keels with food colouring dyed water to see where the water is getting through. As i have found a small hole lower from the top of the keel that might be letting in water.

I am unable to lift the boat so will have to do the work with weigth on the keels. As you said working from the inside out would be a good idea as the areas could have strength added to the inside before i start removing cracks from the outside. Or am i asking for trouble with this approach and should have the boat lifted while i work on it?

 

[oops!]

Re: Encapsulated Bilge Keel moulded to the hull stress cracks. Keel Strengthen projec

hi martin.....and again......ask away !

sorry for the grp confusion....there are so many possibilities that is just wanted to make sure.

the best thing is to get pics up.....as each job can be different.

what is your supply of glass like?....can you get speciality glass ..like a tri ax?...

ok......first off.....to do any good glass job......the sub straight (your hull) must be ground off till you are at glass only.....no epoxy putty.....
if you do find that you need filling as in a scar.....use the structural peanut butter recipe in the thread i gave you.....milled fibres and 1/4 inch short strand fibres.
this will give you a very hard structural putty.
if there is any epoxy on the boat.....and you wish to continue with epoxy, you can......but only use epoxy fillers....then your fibreglassing must be done with epoxy....epoxy and poly do not like each other...so once you start with a product.....stick with it and do the whole job with it.....

I dont like using epoxy because of the long cure times...but it is an excellent choice for your repair.

the two different products use different approaches.

I will start with a lay up schedule for poly..... this is for the outside only at this time......

grind the hull till all contaminants are off the glass.....any paint, old resin. filler.....anything....you want the new lay up to bond to the old glass.....
if you have a crack 1/4 inch wide by 15 inches long...... you will grind 6 inches wide by 20 inches long....

if you want to re enforce the keel at the pressure point....and make the area stronger by using glass.....then grind the whole area....a couple of feet wide by (the length of the keel)
by a few feet deep and up the hull shy of the water line.

after you grind the area......wash the area with acetone. good and clean..... then use a rag dipped in styrene and wipe the area.

wet out the area liberally by applying resin and brushing it in, in several different directions.....the resin will try not to stick at first, so make sure you brush or roll it vigorously in different directions. you want the resin to contact the hull completely with no possible areas of non contact. (the first wet out is important)

apply your first layer of chopped strand matt, a (.75 or one oz) to the area.....this will be a smaller piece than the area.....if you are repairing a crack.....this peice is just the size of the crack.....1 inch by 15 ins wide. if the keel is being done.....just the area of stress or maximum pressure. roll that in with your resin roller till the glass is fully saturated.....but with no resin pooling.......the less resin the better....your next layer will be a 1708 bi axe (tri axe if you can get it) the same size of the csm.

you want to do this several times.....with each layer being larger that the last........there must be csm between each layer of glass cloth. the following layer of cloth the same size of the csm. if you are doing a re inforcement. these areas are much larger.

use your resin roller to make sure there is no air between the layers. you can do as many as three layers of the heavy cloth over each other, but if you do more...the resin will get to hat during cure and become brittle. so after 3 csm/1708 layers. stop till the glass semi cures and the heat has gone out of the cure before you start again.

if you are doing a full keel pressure point area.....the final layer of 1708 will be much larger than the one you first layed......and fully cover the entire surface that you ground off.
it will also need to be finished.......so on top of the 1708 add another layer of csm, and then a 6 oz woven finishing cloth.
this will give you a very smooth final layer to add your filler to or sand for gellcoat.

3-5 sandwich layers will be fine for the re enforcement area. a good long final layer running from the mid point of the keel to below the water line, will be great.

if you choose to use epoxy.......just leave the csm out.....you dont need it. and it will actually make things harder for you.

if you are able to get to the inside as well......a similar 3 layer sandwich of matt.cloth will work fantastic......and all your holes will be gone.