1:28 J Class Enterprise - build log

Other Scale Sailing
41

Disaster!!

Having done a bit more reading around on the net, the impression given was that some release waxes will react with acrylic paint. I prepared my test piece, finished with 3 coats of acrylic gloss, wet sanded etc etc, and then applied 8 coats of Meguiars release wax (number 8). No reaction with the paint so, so far, so good. Then had a nightmare getting a coat of PVA to stick to and cover the waxed surface. Trial and error eventually resulted in a continual dabbing action over the surface while it was drying. When fully dry I applied a 2nd coat with sponge by gently wiping over the surface. At last, a respectable finish.

I allowed the PVA to dry overnight and then set to with a lamination trial. I layed up 4 layers of 175g/m2 glass and left it for six hours. Separation was easy enough but the surface of the ‘mold’ was rough as hell - basically the pattern of the glass cloth weave has left an imprint in the acrylic paint. I’ll post some pics later to show the final outcome.

At the moment I can’t decide whether to re-sand the plug and get it back to the glass layer, hoping that all traces of the paint are removed or give it a light sand and then put another layer of glass over everything to encapsulate the problem - I’ve decided not to go down the tape route for the time being because I may want to produce a mold from the plug rather than just a female hull. Any thoughts?
Regards,

Row

42

Feel for you Row, tough call without knowing the condition of the plug but if you decide to sand it back using the paint as tracer you could well end up with better plug to make female mould, then you can forget about sanding outter hull for good finish (without paint) and you can easily apply peel ply for better binding of hull fit-out.

Not to forget you can always sell further hulls off the female mould, seems to be major hurdle for everyone building J-Class to sucessfully get past hull making stage, without encountering problems.

Cheers Alan

43

The only suggestion I can give is to make for this type of hull a double mold. This method is much more easy to open .
The carton wedge was supported with some carton ribs glued with paper glue easy to remove with water.
See pics
Cheers
ClaudioD

44

OK, so I’ve spent the last week ‘mulling’ things over and generally swearing at the test piece every time I went into the workshop…

Anyway, I sort of made a decision. Part 1 is that I’ve emailed my local supplier to ask if I’d expect a similar result using epoxy resin (they supply the WEST system) and I’m hoping for a reply on Monday. Think I already know what the answer’s likely to be which brings me nicely onto part 2.

The intention is to re-sand the plug using 400 grit wet & dry paper to give the surface a good key and then encapsulate the whole problem with some 165 g/m2 twill and then refinish the surface. I think this is probably the best route as I’ve said before eventually I’d like to take a female mold from the plug (same as Claudio’s ‘Tuiga’ moldings in the previous post). Also, I’m not totally convinced that I’d be able to remove all traces of the acrylic filler primer & topcoat.

Anyway, photos below show the outcome of the ‘experiment’ - I think they’re fairly self explanatory.

Claudio - I made an assumption that the plug in your pictures was ‘Tuiga’. You really have produced an incredible piece of work and it’s well upto professional standards (like all your work). The time and effort that must have gone into producing it is certainly a lesson in patience and I sincerely congratulate you. Have you produced any hulls from the mold yet?

Alan - my thanks for your sympathies, I’ll certainly learn from this fiasco and hopefully others new to this hobby can also learn. Not sure about selling hulls though, it would feel wrong knowing that it’s not all my own work - Claudio did the really difficult bit in my eyes by producing the modified drawings and making them freely available. Also, I don’t yet know if my workmanship would stand up to close scrutiny!!

Anyway, those pictures -

Regards,

Row

45

ROW - only a guess here - but if you used polyester resin on your first attempts, it is very possible the MEK hardener reacted with the acrylic paint. Epoxy can do similar if acetone or lacquer thinner is used in any form as a solvent.

Keep in mind, when playing with “chemicals” - you are trapping some of the chemical properties under/between the glass cloth and the base plug. If the glass portion kicks off, but fumes are trapped between - it is possible those are what is causing your cloth to imbed itself in the paint. If you leave a cloth rag with lacquer thinner, acetone, etc. lying on a car finish long enough, the chemicals will attack that paint as well.

Just a guess.

Second thought - if you are covering a plug with cloth to form a hull, why bother with the paint - just surface finish the outside of the cloth. If you are covering the hull as a “plug” to make and pull a cloth hull, consider covering the plug with plastic packing tape being sure to overlap edges slightly. When you remove the cloth (glass or carbon) from the plug AFTER you finish the exterior, there may be faint lines of the overlap, but they are so fine they won’t show through the cloth. If you are trying for a colored hull - add colorant to the resin and the color will remain when hull is removed from mold.

46

Yes Row is the Tuiga , started some years ago , produced a couples of hulls and all over deck and deck stripping planking and then stopped because of hillness and since I diverged on others models like the design and promotion of the AC-120 , followed by the JClass Enterprise master hull construction, the AC-100 /A-B-C-D and now the CD-43". Once finish this late, I will go back to the Enterprise project and carry on with direct lamination of the hull in two halves, previous coverage with packing tape as mentioned by Dick.
Cheers
ClaudioD

47

Dick - appreciate your thoughts on the issue, they may well be guesswork but they do sound plausible. Regarding your comments on the use of packing tape, Claudio has also suggested that in an earlier post and if I were ‘just’ going to produce a female hull then I reckon it makes perfect sense. Part of my plan has always been to eventually use the plug for the creation of a female mold which will obviously require as near perfect a finish on the plug as is possible which I don’t think will be achievable using packing tape. I should point out that there’s no particular reason for the production of a female mold other than the challenge of producing a gelcoated hull with a flawless finish. I could well be setting myself up to fail - time & rather alot of polishing will tell!!

My original idea of giving the plug a high gloss painted finish was purely to establish whether or not the finish was perfect. Whilst our finger tips may have some phenomenal number of nerve endings I’ve seen plenty of full size production yachts which on close inspection look to have beautiful gelcoat finishes yet with light falling on them at certain angles show a pronounced ripple, something far more apparent in dark colours. I’ve always felt the effect cheapens an otherwise fabulous shape / design and was determined to avoid it at all costs. Further research would seem to indicate that had I used a 2 pack polyurethane or epoxy paint the issue probably wouldn’t have arisen. Unfortunately neither lend themselves to home application without the use of quality compressors & spray guns which I don’t have. We live and learn…

Regards,

Row

48

Claudio,

At the rate I’m going your ‘Enterprise’ will be on the water before mine!!

As you’re aware, I’ve been following your CD-43 thread with great interest and if the sailing trials go well it’s definately going to be my next build.

Regards,

Row

49

Just a quick update. I’ve been giving Dick Lemke’s comments quite a bit of thought recently and when put together with the response I received from my suppliers there certainly is some added plausability to his thoughts. In the email to my suppliers I outlined what had happened with the trial samples and they felt the reaction was caused by either the MEK catalyst or the styrene in the resin. They went on to suggest that, although they’d never experimented, it was possible that using an epoxy resin would give ‘normal’ results as most epoxy formulations do not contain solvents, hence there would be less likelihood of a reaction with the acrylic paint.

So, with this in mind, this evening I’ve ordered some epoxy to try with some more test pieces. The epoxy probably won’t be here until early next week, but once the sample piece is ‘done’ I’ll post the results here.

In the meantime, I hope you’re all enjoying some fantastic sailing weather…

Regards,

Row

50

So the samples took a little longer to complete than initially thought - too many other demands on time and so too little workshop time…

Anyway, one observation that immediatly comes to mind is that epoxy resin & slow hardeners are not for those of an impatient disposition, certainly when compared to polyester resin!

Back to the detail of this latest experiment.

Preparation of the panel was a couple of thin layers of polyester filler which was dry sanded finishing with 320 grit. This was followed with 4 coats of acrylic filler primer, cut back with 400 and then 600 grit wet & dry paper, and finally 3 coats of satin finish (it was what I had lying around) black acrylic spray paint which was flatted back with 800 grit wet & dry to get rid of the ever present orange peel effect from spray cans.

The first picture (hopefully) shows the prepared sample, with the lefthand side just waxed with 6 layers of meguiars number 8. Righthand side also has 6 layers of wax but has also been coated with PVA release liquid.

Second pic shows the samples laminated (rather badly - in a hurry) with an epoxy with slow hardener.

Final pic shows the two samples ‘de-molded’ after approximately 13 hours of cure time. The resin is a ‘generic’ ambient cure laminating epoxy, which can benefit from a 60 C post cure for 15 hours. Additional info at http://www.easycomposites.co.uk/products/epoxy-resin/EL2-epoxy-laminating-resin.aspx

Last thoughts/experience for the time being are that when I came to de-mold, the wax only sample was slightly more difficult to break the surface tension when compared to the PVA’d sample which was expected. In fairness though, on close inspection the overall finish of the panel was not quite as good on the waxed only side when compared to the wax + pva.

So, the disaster from my earlier experiment using polyester resin has now been overcome and I can only assume that the main reason was the solvent free make-up of the epoxy. My thanks to Dick for triggering a thought process which has resulted in not having to apply an additional layer of glass/resin to the plug which would have resulted in having to put in the additional time for refinishing. Happy days !!

Regards,

Row

51

Photos to follow but a quick update…

Having successfully trialed epoxy resin over acrylic paint I set to waxing the plug. Lost count in the end but it had at least 8 ‘coats’ of Meguiars Number 8 release wax. Final coat was allowed to dry overnight (probably not necessary) and the laminating commenced.

1st layer was 165g/m2 glass twill with an approx 30mm overlap down the centre line. 2nd lamination was 290g/m2 glass twill but this time carefully trimed to the centre line. The main reason for this is that I didn’t want to build up undue lamination thickness either side of the line. Also, the weight of the cloth wouldn’t lie evenly over the fine bow sections. 3rd lamination was 165g/m2 glass twill once again but this time with an approx 40mm overlap either side of C/L. The aft face of the keel was left open to assist in de-molding (discussed earlier in thread and also in Claudio’s ‘Enterprise’ build log).

It was at this stage that I made a bit of a mistake which I’ll cover later. Anyway, once I was happy with the glass work and sure that the cloth was fully wetted out I consolidated the laminating with a bristle roller which had been recommended by my supplier. Following this I used a squeegee to remove excess surface resin and then started laying on strips of peel ply. This is when things started to go wrong.

As the peel ply was layed on it soaked up the last remaining excess resin BUT there were one or two dryish patches, so I mixed a little more epoxy and started to stipple it on with a brush. This in its self wouldn’t have been a problem. Unfortunately I started rushing - we were going out & I was running late. Happy that the peel ply looked even I shut up the workshop and left it all until the following morning.

So, 15 hours later… On removing the peel ply I was faced with the mess from hell. Pooling and runs were abundant and lets face it, epoxy puts up a pretty fierce defence to sand paper. Why on earth didn’t I squeegee again after the application of the peel ply? I’m almost embarrassed to post the pictures but I’ll add them to this post sometime over the next few days. What to do?

Ignoring my ‘faux-pas’ for the time being I decided to see if the ‘hull’ would release from the plug. The first gentle upwards tug midships resulted in a fairly easy separation of the topsides and initial inch or so of the turn of the bilge. I then took a strip of softwood (planking offcut) approx 1.5mm x 3mm x 250mm and eased it between the hull and plug at an angle of 45 degrees. Repeated 2-3 times down each side resulted in the separation of the rest of the bilge but still no sign of the keel area separating. The same size strip was then inserted through the open aft face of the keel and result!! Separation complete and the molding lifted easily away from the plug. Others on this forum had suggested that separation could be problematic and although I was inclined to agree with them, on balance I felt it was worth a shot and fortunately it paid off.

The hull was then placed back on the plug and I began sanding with 60 grit paper to start removing the excess epoxy. After an hour or so progress was virtually un-noticable. A bit of a rethink was required…

The inside of the moulding is virtually flawless (1 or 2 very small areas requiring remedial attention) which got me thinking. The outside is so bad that I reckon the easiest option is probably to add additional glass and battens etc to strengthen it further, split it down the centre line and use it as a female mold. I can’t foresee too many problems with this solution but if others have any other observations and/or suggestions they would be gratefully appreciated.

Thats it for the time being - I’ll add some pics over the next few days.

Regards,

Row

52

Row -

if you run into epoxy drips again, take a plain piece of single strength window glass and break into pieces - not with glass cutter. Pick one of the shards of glass, examine for curve or straight edge need and holding at about 30* to surface draw glass along and over the drips. It works very much like a plane, but doesn’t clog like sandpaper. When you notice the cutting action getting harder, just grab another piece of glass with sharp edge and keep going. This will work on glass or directly on wood. You will be amazed at how smooth of finish you can get. Suggest trying on scrap of wood so you get the feel of the proper angle. Not much down force needed - let the sharp broken edge of glass do the work.

I happened on this back when I was cross country skiing (to level racing wax without a hot iron) and then found it worked great on wood. Thought I was a genius until an old woodworker friend clued me in it was kind of a well known process to get base level done before spending time on a plane. Same reason - no sharpening needed.

Good luck, Dick

53

Hi Dick,

Thanks for that, it sounds a bit like a low tech cabinet scraper and I’ll certainly be bearing it in mind for future ‘mistakes’.

When I get round to posting pics I think you’ll realise that my not so small issue with runs & pooling etc is perhaps a little too far gone for basic remedial treatment!! With the quantities I’ve got to deal with I think an angle grinder would be a more appropriate tool for the job. Anyway, the learning curve on this one has certainly been a steep one and at least I know where I went wrong.

Pics soon.

Regards,

Row

54

Row
Sometimes we fall into the trap of trying to repair something when the expedient course is to turf it out and start again.
Don

55

YUP ! Also, visit a floor refinishing shop or purchase on line - some 80 grit floor sanding disks. These work great for rough shaping foam hulls and also cutting epoxy drips. Use the scraper for both “green” and cured epoxy. Use the coarse paper only for hard epoxy.

I agree with Don - having just parted with a main hull for 48 inch trimaran. I found out how thin I can make the hulls before tearing/holes - and it isn’t a layer of 4 oz and a layer of 3/4 oz cloth ! At least I know what NOT to try again. Lighten til it breaks - then don’t go “quite” that far next time.

56

Almost certainly wise words, Don.

Since my last post I’ve done a bit more sanding, experimenting with different types of grit/papers. The most effective, which I guess is comparable to Dick’s suggestion of flooring sander disks, seems to be 60 grit belt sander belts. They cut through the epoxy relatively easily without clogging too readily. Mind you it’s incredible how quickly the epoxy takes the ‘sharpness’ off the belts.

At the moment I’m beginning to think that the molding may be rescue-able with a further couple of hours sanding followed by epoxy fairing compound. In the meantime (tomorrow hopefully) I’ll get some pics taken and get them posted here.

Regards,

Row

57

The dreaded results…

I think they speak for themselves really, but a few comments anyway.

First off, these pics represent about 3 1/2 hours of sanding with nothing finer than 60 grit aluminium oxide type paper. Fortunately, there seems to be a change in pitch of the sanding/scratching sound when attacking the rather thick epoxy as it all too slowly gets back to the outer layer of glass cloth which at least has the advantage of not removing any of the structural laminate.

When the laminate was initially de-molded the hull was trimmed back to approx 2 mm of the finished sheer line and almost flush with the aft face of the keel. 1st couple of pics show the laminate on the plug, vital for heavy sanding and not losing overall shape. The rest are general shots of the hull on its own from various angles. Last pic is a close up of what is left of the worst excess epoxy still left to deal with.

I should also point out that in its current state it looks one hell of a lot worse than it actually is - so much so that I don’t think it’ll need more than another half hour or so of 60 grit sanding before I’ll be ready to start the filling and fairing. Although I used polyester fairing compound on the plug, as the lamination is epoxy I’ll stick with that mixed with WEST microlight fairing additive and then see how it turns out. Obviously I don’t really want to be left with a hull thats got more fairing compound than laminate so any decisions regarding changes in direction (convert to female mold or scrap) will be taken after the fairing etc.

Interestingly, when I first demolded the hull and did the initial trimming it topped the scales at 658 grams. Today, after rather a lot of sanding, it comes in at 596 grams! My initial calculations for the chosen layup schedules gave a target weight of appprox 575 grams, so although the shoulders and arms are getting more of a work out than I anticipated the overall weight is pretty much on target.

One final observation which is more for the ‘newbies’ like me, but I’m utterly amazed at how the hull has stiffened up over the last 3 - 4 days. When it first came off the plug it was incredibly ‘floppy’ for want of a better description and my first thoughts were have I used sufficient overall weight/layers of glass. It’s now completely different, almost to the point when once the inwhales have been installed it’ll only need a couple of bulkheads and the deck to achieve something plenty stiff enough - although I’ll have to see how the ballasting goes before any final decisions are made.

Regards

Row

58

Hi ROW,

Have been away for few weeks holiday and just catching up on your build, firstly glad to hear the single mould keel separation worked out well, but really sorry to hear that “other activities” took away from critical lamination stage after laying on the peel ply…shet happens as they say !

Personally I would not use such heavy cloth on critical hull form, I’m inclined to use lighter clothes (80-100 gsm) just for the tighter weave, holds less epoxy and easier to wet-out & less prone to pooling & running due to the tighter weave not holding so much epoxy.

Apart from trying to recover 1st mould, other option of course is to make another single mould hull off the plug again (scrap 1st hull) …making sure more time to keep an eye on post lamination care.

Other option with the inside of the mould being flawless I thought about reverting back plan B with Claudio’s suggestion of “type of hull a double mould” (post #43) immediate thoughts are the flange on two moulded half’s could be a challenge & wondering if splitting the male mould would be better option ? At least you could have better flange for joining the two half’s.

Cheers Alan

59

Alan,

Hope you enjoyed your holiday, did you manage to mix any sailing with it?

My thanks for your comments - at the moment the ‘recovery’ operation is progressing well, if not a little slowly with other demands on my time. The following stats will almost certainly horrify you in an AC120 mindframe, but here goes…

As mentioned in an earlier post, the molding weight, post sanding, was 596g - the original target weight being 575g. After the first fill & fair process this increased to 618g which unfortunately took rather a long time to get back down to. The instructions for WEST microlight suggest that an ideal mix is similar to that of peanut butter. When I started sanding I couldn’t understand why the so called fairing mix was so hard until it occured to me that I really didn’t have a clue what the consistency of peanut butter actually was! Needless to say the mix was rather heavy on the resin component. Today I managed to get a bit more workshop time and went over the molding again with a better idea of what pnut butter looked/felt like - I bought some in the local shop yesterday. It’s quite incredible how the volume of the mix increases when the correct quantities are used.

Anyway, hull has now had a good covering of correctly mixed compound and it’s now in the laundry cupboard curing at 28C which will hopefully allow a 2nd bout of sanding tomorrow. Ambient daytime temps where I am are struggling to get much above 17C and its amazing what an impact that has on cure times. I’m currently thinking about making a low bake oven from a few sheets of insulation, a light bulb and a fan before she who must be obeyed realises whats going on in with the laundry (I have wrapped it in polythene bags).

Will add some more pics once I’ve made a bit more progress.

Regards,

Row

PS: Thinking a little further ahead to the rudder stock & tube - any recommendations as to materials? Brass ? Aluminium? Carbon fibre? Should the stock be solid or hollow? Advice/ recommendations appreciated.

60

Hi Row, It was campervan holiday though Italy and managed to sneek two boats into the garage compartment without upsetting the bosses nick-nacks and meet up with Matt in Rome for two days casual sailing and few old days on lakes here & there, was cahce to stretch legs of new build Blackmagic NZL 32, still fine tuning but looking good so far :slight_smile:

You’re using epoxy type filler for fairing ? noted you’re talking about curing times and temperature I have been using super light weight two component filler, it’s a paste that your 1-2% harder …bloody good stuff as it goes off in 5-10 mins and after 20-30 mins you can use be sanding it with minimum effort.

In colder months I’ve been using thick cardboard box picked up from local electrical store they use to pack freezes & T.V etc in, taped it together and works perfect, pays to run low speed blower to circulate the inside as light bulbs can reach incrediable high temperatures and can get hot spots, run a thermometer to keep eye on temp.

For the rudder stock I use 4 mm brass tube only because it wears less for the amount of use it gets, interested to hear what others use.

Cheers Alan