Some more progress has now been made, although unfortunately very little in the way of pictures (camera was left at friends’ house and retrieved this morning). After the modification to the aft sheerline hull had a single layer of 165 g/m2 twill cloth applied with polyester resin. I ran a couple of tests to establish working times relative to % catalyst added - one of the disadvantages of polyester resin is the relatively short pot life. With ambient temperatures of around 20 C, I was able to achieve a pot life of 35 minutes with 1% cat added. Beyond that it very quickly started to gel rendering it impossible to work.
Anyway, a paper template was made for the cloth shape required which was then laid out onto the twill cloth and cut around allowing 30-40mm excess cloth around all edges. Once the two pieces (one for each side) were laminated onto the hull (used a 1" brush) and allowed to harden the finished surface was given a light sand and a further coat of resin to fill the weave pattern of the cloth. Wet sanding commenced with 300 grit paper to get hull uniformly smooth. I then sprayed on a black guide coat over the hull before further wet sanding with 400 grit. It was certainly pleasing to note that there were very few hollows which required the smallest amount of filler to rectify. Once the filled areas had been wet sanded I gave the hull another quick flash over with the spray paint for another guide coat which was wet sanded again which showed no further hollows.
As the initial intention is to pull a ‘female’ hull from the plug the finished surface was probably more than adequate (wet sand 400 grit) to apply mould release wax etc & start laminating. However, I decided that I may want to use the plug to make a female mould to enable a male hull to be laminated which requires a far superior finish…
Which brings me to a few days ago. Plug was given a 3 coats of filler primer and then flatted back with 600 grit wet & dry. I then sprayed with an acrylic black gloss, following instructions on tin (10 mins between coats etc). I’ve done a bit of spraying in the past using a decent spray gun & compressor and was able to get reasonably pleasing results. At this point I’d almost go as far to say that spray tins (or at least the nozzles) are NOT fit for purpose! The first attempt was appalling. Runs & overspray was everywhere and of course the dreaded orange peel effect. After much swearing etc, I set down to more wet sanding to flat it all back and spray again.
Anyway, to show where I’m now up to, see attached pictures - the results this time have come out reasonably ok. Only one run to deal with (hopefully first picture?) with an acceptable level of orange peel.
Thats it for now,
Row
Additional stuff:
Another reason for using the black gloss is that dark colours show up imperfections in the surface finish far more reliably than light colours. It’s also worth bearing in mind that I think you can only get so far with ‘finger tip feedback’. Before the glassing was done I was longboarding the plug with 240 grit aluminium oxide paper and the finish felt incredibly smooth. It was only when light coats of spray paint were applied that the true finish was shown, and it’s really disheartening when it ‘feels’ so good.
A quick question on wet sanding etc - The highest grade paper I can get locally seems to be 1200 grit, which followed by polishing compounds seems to give pretty good results. Is it worth sourcing 1500 & 2000 grits for improved surface finish?
I know that Alan’s getting amazing finishes using the ‘German Latex’ method & it’s unfortunate that ‘Enterprise’ and other traditionally shaped hulls aren’t suitable for this. Looking forward to any advice etc & now it’s back to the wet sanding…
Hi Row
Are you going to paint the boat? Is far as I can see ther is no point in going to a superfine finish with the plug/mould if you are going to scuff up the boat so the paint will stick.
Don
Row ,
Just a little warning , If you are laminating directly onto the master, be carefull because polyurethane paints , if any, are often stiking to the fiberglass resin in spite of any layers of wax or PVA !!! . Better to cover it with packing tape !
ClaudioD
In answer to your question, the initial hull will be pulled straight from the plug and will be painted, so the highly polished finish will be of no benefit whatsoever - if anything it could be considered a hindrance as areas of the hull that’ll require bulkheads or fittings will need to be well sanded to enable additional laminating or epoxy bonding. If I do decide to produce a female mould then I’ll probably put in a coloured gel coat as the initial layer so the polished finish becomes beneficial otherwise I’d agree with you 100%.
Obviously for model rc yachts designed for racing a painted hull is much more preferable to a gel coat because of the potential weight savings however, from Claudio’s first post from his Enterprise build, http://www.rcsailing.net/forum1/showthread.php?5781-1-28-scale-ENTERPRISE-1930 you’ll see that the designed displacement is 6167g with 3900g of ballast which leaves 2267g in the ‘budget’ for everything else. The layup schedule will influence the spare weight available, at the moment I’m thinking 2 layers 165g/m2 & 1 layer 280g/m2 which gives an approximate hull weight of 680g leaving 1587g for reinforcement, deck, rc equipment, batteries and rig. Does that look do-able? This is where my inexperience building these things comes into play - at the moment I’ve no idea what the rig & sails will weigh, or for that matter the deck (it’ll depend how much detail I decide to incorporate - planking, deck houses etc) so yours & others comments will be gratefully recieved.
Claudio,
Many thanks for your warning - my intention is to do a bit of experimentation before laminating the hull to see if there is any untoward reaction/sticking between the spraypaint, release wax (Meguiars Mirror Glaze 8) and the resin. With hindsight, I should of done that first otherwise I can see that I’ll have to wet sand off the paint finish to get it back to the glass/resin finish and go from there. I’m keeping my fingers crossed !!! Alternatively, if I have to use packing tape, do I still use release wax and PVA or is it ok on its own?
I have some advice on the laminating… When you are using polyester you do not have to try and layup all the hull layers in one mix. I would weigh out 3 pots, and have the catalyst on ‘stand by’. Mix the fist pot for the first layer, once it is all wet out, mix the second and apply the second layer using fresh resin. Repeat for the third. Do not use or try to use the left overs, its a good test piece to check the resin has catalysed correctly. This way you can push 1.5% - 2% catalyst which I personally prefer on very thin laminates where ‘exotherm’ is not a problem.
Also laminate in the cool of the morning helps, this gives you more working time… then as the day heats up it cures your job nicely!
This method is tried and tested, as is the wax + pva combination. The styrene can eat into the wax, and lift the packing tape too, so if you have pva, I’d recommend using it.
Many thanks for your input - when I laminated the plug I’d carefully cut out each piece of cloth and weighed it to establish the resin required. Each piece was approx 50g so I weighed out 120g of resin and then mixed in the catalyst. The mix was absolutely fine for the first half of the hull, but by the time I’d prepared to do the 2nd half it was beginning to turn to gel. Chucked that lot away and started with a fresh batch, so lesson learned the hard way!
I’d read about the styrene ‘eating’ into the wax, although the impression I’d got was that it was more of an issue with new moulds - I suppose the wax is potentially being attacked from both sides. I’m guessing that in your line of work polyester resin is a big no-no and that modern epoxy formulations are far more predictable especially with pre-pregs. When I’ve satisfied myself that my laminating skills are ok my intention is to move over to epoxies - locally I can get either WEST or SP115, the 115 being available with attractive discounts. Is there any reason to go with one rather than the other or can I just go with the best value for money?
A quick piece of advice on the resin - SP 115 is okay to laminate with, its quite thin and watery, but a word of warning - it goes off very quickly when combined with glass or carbon fibre. You will need to get a sample and test it to see if you are going to have enough time to laminate the hull.
As for the West - I’d stay away from the ‘105’ series as this is treacle, and serves a a very poor quality laminating resin. If you have the choice, and can laminate swiftly, then 115 is the far better option.
That said, I would be perfectly happy with using Poly for a J Class hull…
I started building boats in a small custom dinghy shop and we made Epoxy and Poly racing dinghies. ( International 14’s & Scorpions) Cheap small plugs were MDF covered with packing tape, waxed + PVA… then the female mould was Black gelcoat 2x glass tissue 10 - 12 x 300 gsm chopped strand mat depending on the size of the mould.
I have just remembered another good product we used frequently to prep a plug surface was called “Reface”. It was a polyester primer. You brushed or rollered it onto the plug and it cured in 20 - 30 mins… Once sanded smooth ( very easy as it was very soft!) you sealed it with wax and applied the PVA… Good to go! Reface is still available today… less than £20 for a litre.
Packing tape I’d recommend is the 3M Scotch brand easy to find and adheres much better than some cheap brands and works well with wax.
Thanks for your comments on the various epoxy products - I’ve just realised that it’s not the 115 I can get cheaply but the 106, so any comments on that one?
I can understand why others use epoxy, especially with rc racing ‘machines’ where for want of better terminology its ‘elasticity’ enables lighter layups than polyester, but I think when you’re not chasing every gram the poly provides a very effective & cheap alternative. My most recent experience with resins go as far as new engine bearers and a couple of stitch & tape projects so this is very much a learning curve & I’m sure plenty will get chucked away. Also, I’m not 100% sure my wife would understand ££’s of epoxy disappearing into landfill because it wasn’t quite right!!
With resin systems… You do indeed pay for what you get and 106 is not very ‘nice’ to laminate with. The fast hardener is pretty fast too - so be careful!
You are right with your point of view that people seeking the next level of performance will gravitate to the higher performing resins, if you feel that it would be beneficial then I would go ahead and use epoxy. If not, then your hull will be just fine in Poly.
personal view … I was able to become good friends with two of the Gougeon Brothers while living in Michigan and racing multihulls. Was fun to “learn” so much about wood composite boats and to this day I am amazed at how advanced and light weight some of their wood creations were in the 70’s and 80’s - plus the added beauty of clear finished woods. What drew and kept me buying their products was the ability to do so many things - it sealed, it coated, it glued, and it laminated - all with one (basically) product that was more expensive, but didn’t smell so I could work inside. Using polyester body fillers at times for fairing when needing fast cure times, usually was accompanied by wife’s complaints.
Also a favorite for my home use is a product called JB Weld which has saved my butt a few times as well. Not sure if available in the U.K.
Thanks Jim, I reckon I’ll be sticking with the polyester for the time being & perhaps using epoxy based adhesives for hull fittings etc. In the meantime I need to get my backside into gear and produce some test pieces, plug sprayed with acrylic paint which I’m beginning to think was not my finest idea - spoke to my supplier earlier today and was informed of a fairly high probability of the styrene attacking the paint however many layers of wax &PVA were applied to the plug. I was under the impression that wax & pva formed a barrier between plug & moulding. Claudio did caution about some paints and waxes - wish I’d researched it a bit more beforehand. As has been said before, theres always packing tape…
Many thanks for your comments & it’s nice to hear that I’m not the only one to get their ear bent for ‘unpleasant fumes’ permeating through the house. We’ve got a double sized garage which is unfortunately an integral part of the house so the noxious odours do tend to get everywhere!
Low styrene polyesters don’t seem to be too bad but polyester fillers (bondo etc) are particularly pungent. I’ve used the WEST products in the past purely as an adhesive and found it relatively easy to use and I’m amazed you’ve had dispensation to use them inside - I’d be shot!
I’m sure any contact with the Gougeon brothers would be phenomenally educational, particularly in the 70’s afterall, they literally wrote the book. My first experience of epoxy was early 80’s at a yard called Curtis & Pape (saddly now defunct) where they were building a cedar strip half tonner using west products - a whole new way of building boats - and was incredibly light & strong. Unfortunately I don’t remember the name of the yacht but it had the most intricate coat of arms inlaid to the transom.
And yes, JB weld is available in the UK, its even sold in supermarkets. Just out of interest what do you use it for?
Row - that “could” be a long list - from automotive (fiberglass tape + JB Weld for muffler repair), motorcycle racing (for broken/stripped out side casing screws and support fillets) r/c sailboats (filler for lead keel bulbs and fairing for a “nicer looking” gooseneck/vang fitting. Also used to fabricate/drill/tap holes for servo attachments-but have since switched to WEST epoxy + aluminum powder inside a small diameter carbon tube. When cured - just drill and tap. Fabricated some rudder fittings for transom mounted rudders.) plumbing (the faucet handle “star” hole was worn, so filled pot-metal handle and coated the faucet “post” with light grease - pushed handle on to form to the star pattern, removed handle when cured and filed/ground off the excess. Pushed a wad of the stuff into a rusted drain pipe hole until I could get to store to replace the entire sink drain.) General home repair (Patched a broken metal screen door handle where push latch release button had worn thin from use). Whew - great stuff.
JB Weld’s great stuff.
I used it to fill parts of some air-soft M16 bodies to so they’d accept real M-16 grips, stocks, etc in converting them to paint-ball guns. http://todd.mainecav.org/paintball/m16/progress
Well it’s certainly refreshing to hear good reports of a consumer product that suffers from appalling TV advertising. I’d always assumed that it was yet another product whose abilities were stretched to the absolute limits of creative license by the advertisers. I’ll definately be adding some to the tool kit.