Reglassing Engine Beds - Any hints for a fibreglass virgin ?

eebygum

eebygum

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Problem was rusted engine mounts and crack in one bearer:
Survey report advised (1) taking out engine (2) replacing rusted engine mounts (3) replacing engine bearers as it there was a crack in the portside bearer (believed to be full length)

Situation:
I've had the Yanmar 2GM20 engine taken out of the Contessa26.

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The screws attaching the engine mounts to the engine beds were taken out. While the engine beds are generally in good solid condition, there is a hairline crack on the portside bed but this only runs for 3" and I think the original holes are too soft to reposition as was. All the engine mounts need to be replaced, there is minimal height adjustment as all were set to the minimum depth. Rear attaching flanges also badly corroded and I've sourced secondhand replacements for £7.50 as opposed to the Yanmar price of £113 EACH !!

Proposed Solution:
Deepen and then fill the hairline crack with epoxy. Fill the old screw holes with epoxy glass filler.
Install with new NON-Yanmar engine mounts which are slightly smaller and screw to a different position on the engine beds.
As the replacement mounts are set to a lower height I plan to strengthen the beds by epoxying a 20cm thickness of hardwood over the full length of the original beds and then glass over the new/old beds.

I will mark off where the original mount holes were to get the right longitudional positioing on the new raised bed.

<u>Dumb Questions for the fibreglass novice:</u>
(A) If I do it this weekend and the temperature is 5C will the epoxy cure OK ?
(B) How many layers of fibreglass do I need to glass over....2,3,4 ?
(C) Can I glass all layers in one go, or do I need to do one layer, let dry and sand then do second etc. ?
(D) I know you can get different weights of fibreglass, do I go for lots of thinner lighter layers or fewer heavy layers; or should I fork out for carbon fibre.
(E) How much should I overlap the sides for strength......2, 4, 6, 8 "
(F) How do I finish off .... a few coats of epoxy and painting with bilge paint
(G) Anything else I should know ???????????? /forums/images/graemlins/confused.gif

Any help and opinions on the above gratefully received before I start work on Sunday afternoon !

Thanks
Andrew
Progress on my boat can be found at:
 
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<u>Dumb Questions for the fibreglass novice:</u>
(A) If I do it this weekend and the temperature is 5C will the epoxy cure OK ?
Yes it will be fine depends what ratio you use on the mixture for curing
(B) How many layers of fibreglass do I need to glass over....2,3,4 ?
depends on how thick the matting is how many ounces do you want to lay? then work out how many complexes you think you want to lay ie time etc and how good you think you are at laying thick or thinner complexes
(C) Can I glass all layers in one go, or do I need to do one layer, let dry and sand then do second etc. ?
You need to let each layer start to cure and once they are close to fully set you can do the next layer.
(D) I know you can get different weights of fibreglass, do I go for lots of thinner lighter layers or fewer heavy layers; or should I fork out for carbon fibre.
take your time overlay by at least 4 inches go for 6 be best the thicker and better the stronger and longer lasting

(E) How much should I overlap the sides for strength......2, 4, 6, 8 "
(F) How do I finish off .... a few coats of epoxy and painting with bilge paint
a coating of resin to smooth things off and the flo coat paint the rest over

Good luck and just be methodical preparation is the key have gloves and mixing pots and good scissors to cut the mat. Use a good thin very thin metal roller to get into every nook and cranny

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1 Never change the ratio of hardner and resin if using epoxy. It must allways be the same no matter what the temp is.

2 5c is too cold and will form amine blush.

3 to get a good bond lay all your glass at once and consolidate with a heavy rolling

4 Min overlap of glass is 100mm

5 Have fun
 
It is far too cold, beg borrow steal heaters and try to keep temperature above 15C, but below 20C (This will give you working time). As a novice you do not want the resin to cure to quickly.

Lay the mat all at once, allowing to partially dry is bad advice and will lead to possible de-lamination.

Always tear chopped strand do not cut it, this stops edges! torn mat becomes part of the the other sheets as you work the resin in.

Wear gloves.

Have a towel handy to wipe face, or scratch with, getting resin and mat around your face is no fun.

Round off all edges of engine bearers etc. GRP does not like corners, use putty if necessary for hull to wood joints.

I have scanned in a useful manual which you might like to download and print out. It is getting on a bit, but the principles are the same.

GRP-REPAIR-MANUAL.pdf
 
Unless British mat is different than that which we have in Canada do not use mat with epoxy resin as the binder will not disolve. Do I understand you use screws to hold the mounts to the bed rather than glassing in a threaded steel plate and using bolts.
 
I confirm that you should not use ordinary chopped strand mat with epoxy, nor should you use carbon fibre as it will reduce strength, not increase it.

There is actually no reason why you shouldn't use polyester resin. If you clean and sand thoroughly (as you would have tofor epoxy anyway) it will bond just fine and by increasing the catalyst ratio you can get it to set right down to freezing temperatures though a bit of heat is ideal.
 
There is a lot of contradicting advice here. There are several things that are incontrovertable though to achieve a good job.
1. For any but extremely advanced specialised resin systems the working temperature (and that means the resin itself, the part to be bonded to and the air temperature MUST be over 16 degrees. Any attempt to work at lower temperatures will result in incomplete cure, adhesion problems and delamination.
2. The part itself should be ground down to virgin material, clean, dry, and at the required temperature before start.
3. Humidity levels should be as low as possible. This time of year they are normally too high. As you probably wont have equipment to measure all I can say is pick a dry sunny day if you can!
4. There is absolutely no advantage or reason why you should use Epoxy for this job. Polyester will be fine and is much easier to work with. Many will argue that epoxy bonds better. Ignore them. Epoxy is far more tolerant and will wet -out far more easily, especially for a self confessed virgin!
5. In terms of laminate, as you have not done it before I would advise to start with CSM (chopped strand matt) and then use a biaxial weave cloth of medium weight (not critical, see what you can obtain) and alternate about three layers of each for a really strong job. allow each layer to cure and become cool to the touch before overlaying the next. Don't hurry. Only mix enough resin for one layer at a time. use a roller to consolidate each layer avoiding air bubbles. Its best to apply liberal amounts of resin to the job first and then apply the cloth and roll the resin up through the cloth rather than apply it to the top. You can always apply more to the cloth if it's not wetted out from below but to apply all resin from above will leave voids. You can indeed apply more layers at a time but there is no reason why you must. If you leave the job more than 72 hours between layers you need to grind back and prepare all over again to obtain a bond so don't!

Other questions you have asked.

Overlap about 4 inches at first tapering off to 2 inches at the top layer to blend.
Finishing with epoxy paint is a good idea but leave the polyester at least a week or two before doing so to allow it to vent styrene or you might get it lifting and bubbling. Bilge paint over is fine.
 
I built new engine beds last winter and totally agree with boatmike. Suggest you use polyester resin, with alternating layers of CSM (chopped strand mat) and woven rovings (biaxial weave). DO NOT use woven rovings only -- they don't bond together well with polyester. Polyester far cheaper than epoxy and more tolerant of variations in catalyst ratio. Best applied wet on 'green' (not fully cured), having thoroughly cleaned and abraded the area to which it's applied. At this time of year, you will need a heater to help it cure.
You may find that the most time-consuming part of the job isn't the actual glassing, but establishing accurate datums and dimensions. Don't take short cuts on this.
You might find books on DIY glassing at your nearest chandlery or even a good public library. A Google search should throw up plenty of info, too.
 
Well thanks for all the advice which is invaluable and has certainly helped me reconsider my approach.

As a fibreglass virgin I've concluded that ........there's lots of different ways to do it....take your time..prepare by measuring up.....don't rush it.....be safe and use protection....best not done in the freezing cold....rest and harden slightly repeating process....don't leave it more than 72 hours between sessions. Hmm sounds familiar in some way /forums/images/graemlins/blush.gif
 
Sorry you are quite correct. I should have said POLYESTER is far more tolerant. Apologies and thanks for pointing out my dumb typo...
 
Or whoever... Scott Bader et al will be pleased to suply material specs, methods etc and give sound advice too. If all else fails read what it says on the tin! If there is now't on the tin ask for a material data sheet.
 
Above all you need to do the job properly. Do not undertake it lightly. Glassfibre work like everything else is easy when you know what you are doing. Equally easy to make a total cock-up. Get the manuals and study them before starting.
 
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I have scanned in a useful manual which you might like to download and print out. It is getting on a bit, but the principles are the same.


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Five Shillings ! !

That is getting on a bit ! !

/forums/images/graemlins/blush.gif /forums/images/graemlins/blush.gif
 
If you are doing one layer at a time use waxless resin. To do all layers at one go waxed resin would be better. With waxless resin the top layer will be tacky for a long time.
 
Sorry but you must not put wax (MW) in resin, resin will allways dry hard unlesss you are vacuuming but thats another subject. Wax should only be used in gel coat,as it will not dry totally without it.
You can lam rovings as long as you put CSM between layers, or use combi mat.
Hope that is of some help.
 
In Canada we have both waxed and waxless resin. The last layer of resin hardens, that is becomes untacky because the wax floats to the surface to cut off the air. If waxed resin is used and then left to harden (dry) the wax will impede the next layer. There is no mention of gell coat but only of paint Our waxless resin stays tacky for years. But then perhaps this is different in the U.K.
 
To clarify:

Standard laminating resin contains some wax. The reason for this is that the resin is inhibited by air so the top surface will not fully set unless air is excluded. The wax comes to the surface and forms an air-excluding layer allowing the surface to set. The wax layer is the reason it is essential to abrade before applying fresh resin to a cured surface.

Under normal circumstances you want gelcoat to stay tacky until you lay up the laminate onto it. For that reason gelcoat contains no wax.

The only normal reason to add wax is to allow gelcoat to set when it forms the top layer. That is called the 'flow coat'.

If you used a waxless laminating resin for intermediate layers it would save the sanding process but that is a specialist resin not normally available through DIY outlets.
 
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