Fiberglass and boat design question

[MCL]

Im in the middle of a engine change on my 1990 glastron sierra 199.Its my first serious boat,im technical but a beginner when it comes to boats and fiberglass.Im from Finland so my english is not so good.

In the bottom of the engine compartment there is a layer of fiberglass put on the bottom of the hull so that there is space between the hull and the layer.It looks a bit like a small pillow and its from the factory.There is a broken bracket probably from the original bilge mounted on this layer.My problem is the last owner put a new bilge with screws and used no sealant.Now the space between the layer and the hull is filled with water and oil.I know that water will break the polyesteresin down and want to fix this issue before it gets any worse.The fiberglass is still hard and elastic.


What im wondering is why would they make this "pillow" from the factory,is it to mount the bilge on without having to fear to drill thru the hull?
I want to cut the whole "pillow" off so that only the bottom of the engine compartment(hull?) will be left,epoxy a fiberglassmat on it and paint it with some epoxypaint like the rest of the engine compartment.Does this sound like a good solution?Also ive heard that epoxyresin will attach to dry polyesterresin but not the other way around,is this true?

Also there are two spots on the boat above the waterline where there are very small cracks in the topcoat(gelcoat?).What could cause it?Is it serious and how do I fix it?

Hope you understand.I dont have any pictures at the moment to clarify the issues.

 

[MCL]

Re: Fiberglass and boat design question

http://i292.photobucket.com/albums/mm1/MCL-thumpertalk/engine-1.jpg[/url]

Actually found some pictures of the boat.First pic is off the boat,you can see that it is in great condition.The second picture doesn show the "pillow",but it is under the pulley in the middle of the V hull.Its size is maybe 5x8 inches.

 

[RWilson2526]

Re: Fiberglass and boat design question

First off lets start with saying your english is PERFECT....I mean its better than a large portion of many people born and bred here.

I think you are exactly right about the purpose of the fiberglass "pillow" . I would cut it off with a grinder and do what you said for a fix.

I also believe you are correct about the compatibility of different resins to each other....cant say if you have it right but I do remember that you can do one to the other but not the other way around ...just not sure which way...do a little research and you'll probably find it.

As far as the small cracks in the gelcoat its proably nothing to worry about. Are they at corners or just right in the middle of a smooth surface?

 

[MCL]

Re: Fiberglass and boat design question

Well thank you,I do try to write as good as I can.

Its always good to confirm before sticking your head out and ruin something.I will ask the shop about resins as I buy the fiberglass and other materials for the job.Im going to attach the bilge with some adhesive that will keep it in place,yet be able to remove it if needed.Im not a big believer in drilling in fiberglass.

I think one is in a corner and the other is on a rough flat surface,does it matter?

 

[RWilson2526]

Re: Fiberglass and boat design question

well the cracks in the corner are very common and definitely nothing to worry about...corners take the most stress when a boat flexes while moving and most manufacturers will call that "normal". You really shouldn't get any on a flat surface unless somebody bumped a dock or something...if its not extensive and not getting any bigger I wouldn't worry about it.