Project #1

[G_Kay]

Hi there

I have recently purchased a 14' speedboat hull as a project and have a few questions which i need answering.

The boat is a 14' x 5' fibreglass hull speed boat and the manufacturer is unknown to myself, however the boat was sold to me as a bristol channel racer. The hull has never been used, assembled, kitted out etc. I'm starting with a blank canvas.

So my questions are as follows. Inside the hull there is an epoxy/resin type substance been splashed and spilt which has created a bit of a pitted and knobbly surface.
1) Will this surface need to be preped or taken back to the parent material to provide a smooth working surface off which i can install the structural work?

2) What is the optimum bonding surface smooth/slightly rough?

3) If using a foam based stringer system would the surface not need as much preperation as a wood based system.

4) And finally, what is the best method of removing all the unwanted rubish on the surface of the hull?

Thanks for all your assistance

G_Kay

[BHOFM]

I think some photos would be of much help in getting
some advice??

[G_Kay]

Thanks for your responce.

I'll try and get a few photos on to show the previously mentioned hull condition.


PS. Is the clock makers comment meaning i'm possibly biting off more than i can chew?

[G_Kay]

Whoops, sorry just relised its your signature.

Been a long day.

[BHOFM]

Originally Posted by G_Kay

Thanks for your responce.

I'll try and get a few photos on to show the previously mentioned hull condition.


PS. Is the clock makers comment meaning i'm possibly biting off more than i can chew?

No, not at all, just it is hard to see with words some times.
I think you have asked the right questions, we just need
some the pro's here to look and give the best advice.
If you had a clock to fix or a cheap wooden boat, I would
be right in the middle of it!

[G_Kay]

Attached are a few images of the inner-hull condition.

[G_Kay]

Photos attached this time.

[G_Kay]

Another photo.

[G_Kay]

Any feedback would be really appreciated regarding the fore mentioned issues with the hull of my speedboat.

Thanks

[PAR]

All surfaces that have cured epoxy on them need to be "toothed" up with an aggressive grit, like 16, 24 36 or 40. This abated surface then can receive a bond with new material, set in or tabbed with epoxy.

The optimum bonding surface is raw wood, with a fairly rough texture. I wouldn't use anything more then 100 grit on raw wood.

There are two types of bonds, a mechanical one, which we've been discussing and a chemical bond. A mechanical bond is just as it sounds, the over layer is "keyed" to the substrate with a scratched (toothed) surface, which we get by grinding, sanding, etc. It's not as strong as a chemical bond, but likely stronger then the substrate.

A chemical bond is when you apply more resin over not completely cured epoxy. This is the best bond. Strive to arrange joints and coatings around this simple fact.

Foam or any other material used for stringers needs the same surface prep. The surface needs to be clean, toothed and if virgin material (unmolested by epoxy or other sealer), then wetted out with "neat" epoxy. The neat epoxy will soak into many materials, so wait until you're sure no dry spots show up to piss you off.

Cleaning surfaces is a pain in the butt, but that's why we get married. Use acidic base cleaners to remove the bulk of the grime, then flush the area(s) with water to neutralize and wash off the cleaners. With the loose and the easy to wipe off stuff gone you can move to the grinders with aggressive grits, which also prepares the surface for bonding. Be careful around waxy substances. If you hit these with a grinder then they just spread every where and really piss you off come finishing time. The same it true of silicon. In these areas, use toluene which should eat the wax and soften the silicon enough to remove.

I use a 7" and 10" grinder for most of the bulk surface work, with air files and sanders to get in places the big spinning disks can't.

[TeddyDiver]

Regarding epoxys, there's a chance of aminewax residue on the surfaces. Tap water and brushing..

[G_Kay]

Thanks for your advice.

The surface definately isn't coated with a waxy residue, the spilt material is hard.

So just to recap on what you have said;

1) I need to "tooth up" the surface area with a course grit wheel to recieve new material.

2) I should then clean the inner-hull with a acid based cleaning product.
(Will acitone be suitable?)

3) Apply a new layer of epoxy throughout the hull ensuring not to leave any dry spots.

4) I then need to sand this area with a 100 grit disk (no more cousre) which will give me my optimum working surface.

Thanks once again

G_Kay

(NB. when you say "tabbed" does that mean a brushed on coating of epoxy)

[PAR]

Scrub the surface first, with the cleaner of choice. Not an acid base, but an acidic base, big difference. Plan old orange juice will do, because it's reasonably acidic, but you'll make a career out of it, so something stronger, just avoid the alkalines. Use a cleaner not a straight chemical wash. Whatever your wife has under the kitchen sink will likely get the job done. Do this while she's out shopping, trust me. They treat their kitchen implements much like we do our tools and you might get smacked around. This washing and scrubbing will also remove any blush (the amine wax mentioned previously) that may be there. It's often difficult for a novice to see amine blush.

When the surface is free of loose dirt, spills and other stuff, abate the surface with a rough grit. The rougher the better. Save the 100 grit for areas you want to finish really smoothly. If bonding structural elements (bulkheads, etc.) then 24 grit is all you need and it makes the quickest work of it.

When you're ready to bond a piece to a section of the hull then "wet out" the roughened area to be bonded with neat epoxy first. This is especially important on raw wood as the wood can suck the epoxy inside, creating dry spots, which will leave this area of the bonding surface "glue starved".

Tabbed means there is a strip of fabric along the joinning edges, usualy severial. This serves to make a flange and hold the bonded part in location also spreading loads along a much wider piece of hull and glue line.

Go to www.WestSystem.com or www.SystemThree.com and down load their users guides. They'll go over the basic techniques and you'll learn much about fillers, mixing ratios, bonding to different materials, etc. It's worth the invested time.

[G_Kay]

Will take a look at the 2 websites you have recommended to gain a better understanding of the whole process.

Well i suppose iv'e now got the great task of scrubbing till my heart is content now.

Thanks once again.

[keith66]

I would think it unlikely your small speed boat will have been built with epoxy,
You will not need to use epoxy on it when bonding stringers in polyester will be fine but as Par says sand the lumps off to give a good key. For structural work on the interior of the hull a good sand up with 40 grit disc on an angle grinder is all you need, be careful as they can be rather agressive!
i see you are in the UK, get in touch with Glasplies of southport, they are an excellent supplier of GRP materials at the cheapest prices going and will send you an information booklet on working with the stuff, it is written for the DIY person with little or no experience and is worth its weight in gold. Have fun!