Laying up fiberglass hull

[Kez]

After many attempts, I was able to make a mould out of a deep vee hull of my own design. I would like to make half a dozen hulls so that I can experiment with different set ups (sub surface, surface and outboard) and see how different set up affect the performance.

I have several questions:

1. What are the advantages and disadvantages of fiberglass cloth and matt? My own experience has been that matt soaks up a lot of resin (therefore heavier) and it is messy as I end up with glass fiber everywhere.

2. I noticed commercial hulls (eg Aeromarine and Dumas) used coth in the hull but matt was used for the decks. Is there a reason other than cost?

3. What weight cloth/matt should I use for a .21 hull (about 30" long)? I am thinking: gel coat/3 oz cloth/6 oz cloth/6 oz cloth.

4. I used mould release wax under PVA, as suggested by several books that I read. Problem with PVA is that it fish-eye or bead up over waxed surface, thereby transfering the imperfections to the mould. Can I use only wax? Or only PVA?

Thanks,

Kez

 

[lohring]

What kind of resin, polyester or epoxy, will you be using? If you are building boats in production, gel coated polyester resin layups with a layer of 3 oz. cloth followed by mat produces a reasonable, quick layup. If you want a durable, light weight boat, an epoxy resin layup with 3 oz. cloth followed by two layers of 6 oz. cloth is far superior. You can spray primer in the mold before you layup the boat and get a reasonable surface for paint. West Proset resin is the easiest epoxy resin to layup that I have used. The West coating resins will work, but don't wet out the cloth as easily.

Wax plus PVA gives good mold release with epoxy resins, but the mold needs to be cleaned and recoated with PVA after every part. Wax is enough for polyester resins and the mold will need to be re-waxed after every few parts. I always put a quick coat of wax on after each part to be sure. A better mold release system is Chemlease or Freecoat. After treating the mold with these agents, you can get a few epoxy parts to maybe 20 polyester parts before recoating. There is no cleanup of either the part or mold, and the problems with surface finish are gone. I still put on a quick coat between each epoxy part.

If you use polyester resins, be sure to have very good ventilation. I wear a charcoal filter mask. Epoxy resin will cause alergic reactions in time. Always wear gloves.

Lohring Miller

 

[Kez]

What kind of resin, polyester or epoxy, will you be using?  If you are building boats in production, gel coated polyester resin layups with a layer of 3 oz. cloth followed by mat produces a reasonable, quick layup.  If you want a durable, light weight boat, an epoxy resin layup with 3 oz. cloth followed by two layers of 6 oz. cloth is far superior.  You can spray primer in the mold before you layup the boat and get a reasonable surface for paint.
Wax is enough for polyester resins and the mold will need to be re-waxed after every few parts

If you use polyester resins, be sure to have very good ventilation.  I wear a charcoal filter mask.  Epoxy resin will cause alergic reactions in time.  Always wear gloves.

Lohring Miller

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Thanks Lohring for your inputs.

The purpose of my experiment is not to produce these hulls for business. I have found that the material cost plus the time and effort involved in making a mould and hulls is more than what's available on the market.

I noticed that the decks of most polyester resin fiberglass hulls (Aeromarine and Dumas as these are the ones I have) will develop ripple and sag over time. I am think about sandwiching a sheet of balsa the thrength these large flat area.

I have tried using just wax but ended up locking up the mould to the plug. I think the mould is sticking in the strakes and sharp corner where most of the wax is buffed off.

I have heard of allergy reactions to epoxies and therefore I choose polyester. I do understand that it is dangerous especially the catalyst MEK peroxide.

Thanks,

Kez

 

[Jimmy Whitbeck]

What kind of resin, polyester or epoxy, will you be using?  If you are building boats in production, gel coated polyester resin layups with a layer of 3 oz. cloth followed by mat produces a reasonable, quick layup.  If you want a durable, light weight boat, an epoxy resin layup with 3 oz. cloth followed by two layers of 6 oz. cloth is far superior.  You can spray primer in the mold before you layup the boat and get a reasonable surface for paint.
Wax is enough for polyester resins and the mold will need to be re-waxed after every few parts

If you use polyester resins, be sure to have very good ventilation.  I wear a charcoal filter mask.  Epoxy resin will cause alergic reactions in time.  Always wear gloves.

Lohring Miller

73864[/snapback]

​

Thanks Lohring for your inputs.

The purpose of my experiment is not to produce these hulls for business. I have found that the material cost plus the time and effort involved in making a mould and hulls is more than what's available on the market.

I noticed that the decks of most polyester resin fiberglass hulls (Aeromarine and Dumas as these are the ones I have) will develop ripple and sag over time. I am think about sandwiching a sheet of balsa the thrength these large flat area.

I have tried using just wax but ended up locking up the mould to the plug. I think the mould is sticking in the strakes and sharp corner where most of the wax is buffed off.

I have heard of allergy reactions to epoxies and therefore I choose polyester. I do understand that it is dangerous especially the catalyst MEK peroxide.

Thanks,

Kez

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sugustion use tr(brand) hi temp mold release wax red can,on a green mold the the first part wax5 time's, pva it and and make a part ,then after that just use a good waxing.

i use .75 oz matt for the first layer and one layer of 5 oz cloth and in some areas I use a surface viel matt as it seprates the cloth from the gell as cloth against gellcoat will transfer the cloth pattern to it.i usr a iso resin (polyester)

 

[DaveMarles]

To stop the PVA 'fisheying' on a waxed surface, add a drop of washing up liquid to the PVA.

Epoxy mouldings are far superior to any polyester mouldings but are much more time consuming to layup and of course more expensive. We vacuum bag all of our boats to get the best strength/weight ratio.

 

[Lake S.P.O.R.T.]

I will share a secret with you that will insure that you will never stick another mold to a plug. One of those things that I do that is unusual but works. Wax the plug with hi temp mold wax many times, at least 7 or 8 times. The last coat, swirl the wax on VERY light with the applicator, so light that you don't leave any heavy swirling or ripples of wax anywhere. Do not buff it off.....leave it. Lay up the mold over this. Yes, you will transfer this wax pattern to the mold but it will be so light that it will wet sand out of the mold in no time with 1200-1500 grit paper. Polish mold, wash mold with soap and water then do your wax buildup process in the mold. It is not neccesary to leave the wax in the mold like on the plug.

Also, it is crucial when building up multiple coats of mold release paste wax to wait between coats. Swirl on, let haze, buff off and then wait several hours before swirling on the next coat. Putting on coats without allowing this time will prevent buildup of good individual coats of wax. Just thought I would share that if you are having problems using the traditional wax method.

Mark

 

[P THOMAS]

This is what i use, the key to wax is no silicone this causes the fisheye

I have never sprayed the PVA, just brushed it on with a soft camel hair brush.

You can get anything you need from here.

http://www.fibreglast.com/showproducts-cat...eleases-23.html

PART ALL Paste Wax is a non-silicone green wax specially formulated to produce a tough, durable, high gloss surface. Excellent release characteristics are achieved when used with # 13 PVA. We recommend that new molds are coated with four layers before use. Apply two coats of wax, buff off the excess, and allow to stand for an hour before applying the last two coats. The wait is to give solvents extra time to evaporate so a tougher wax barrier develops.

Inexpensive and Effective Barrier

PVA (Polyvinyl Alcohol) should be used with PART ALL Wax to aid in the release of parts from a mold. It should be applied in three thin mist coats over nonporous, waxed mold surfaces. After the final wax coat has dried, begin by spraying a light tack coat of PVA. Typically, within 5 minutes the final heavier coats can be added. The PVA dries to form a smooth, glassy film. After part release, the residual film can be removed with water. We recommend using an inexpensive automotive siphon spray gun and 70-90 psi for application, although air brushes will work on hobby size projects. PVA can also be sprayed over any polyester repair to provide an airless tack-free cure

 

[lohring]

I would much rather work with epoxy resins. You have a longer working time and there is no smell. Wearing latex gloves is a good idea with polyester resins as well to make it easier to clean your hands.

As others have suggested, the green Partal wax is the one to use. I put on PVA with a foam brush. I haven't tried the soap trick, but Freecoat is so much easier to use that I got away from wax and PVA.

Lohring Miller

 

[Mike G]

Honey wax.

Matt is far stronger for the same weight.

Cloth needs matt between layers to fill the voids.

Cloth is used on the inside for show, it leaves a smooth finish.

Vac bagging will reduce the weight by removing excess resin, the strength is in the matt.

Core matt is better than balsa.

 

[Kez]

Thanks all for sharing your knowledge. These are all valuable information/experience that I will not find in books. Wish I knew all these tricks before I wasted my time and many plugs. This is one great site where I can find experts in all areas when I need help.

Thanks,

Kez

 

[nitrokid49]

Hey there, I build my own hulls with a styrofome mold I have used the mat and the cloth. The clot is much easyer to work with but it is also weaker. I use two layers of mat on my big gas boats and and two layers on my smaller boats. But im really interested in how you made the mold.

Victor

 

[GTR]

Hi Guys

Need to clarify some terminology here - cloth is not weaker than matt, it is not as stiff because the weave only runs in two directions. Solution lay cloth at 45deg in next layer.

Matt requires (soaks up) about 50% more resin than cloth. Therefore weighs more.

Matt/cloth weight refers to weight per sq/m or ft of dry material so not an indication of how heavy after resin is appied.

Epoxy resin doesn't generally need gel coat - less weight

For matt or cloth to not tranfer an imprint to surface you need to use surfacing tissue ( which is really super fine f/glass matt)

Matt does contain a bonder (styrene) that is disolved by reaction with ester type resins.

MEKP is nasty stuff - handle with extreme caution - DO NOT GET IN EYES

Epoxy does have an odour - just not as strong as the dissolved styrene one in polyester.

All in all have fun and learn by experience.

 

[Bob Howard]

I have an old Pro Glass hull that got hit this year in a race. The hull was matt in part of it and cloth in part. When I got hit the matt got a big chunk nocked out and the cloth that was right next to it only cracked a little.

Bob