Yesterday another 4 layers of cloth were vacuumed bagged on the previous days work – a little easier second time arround.

Filler was made to fill some of the gaps where the corner pads are to be placed.  This had to be done twice as some numpty got his maths wrong on catalysing the resin … all good experience.

Today, well deep breath as the balsa panel was ready to expoxy in – all the planning helped, but as ever more challenges presented on the day, one the wind got up and blew the micro fibres everywhere whilst mixing the epoxy.  Secondly positioning the balsa panel laden with 1.5 Kg of epoxy was slightly more tricky.

Epoxy bled onto the vacuum bag, but there was no going back, best efforts were made to seal the vacuum bag, and the pump siwthched on.  Leaks were addressed and the vacuum valve showed a good vacuum :

Looking good, so a vacuum gauge was fitted to the other side of the setup, and this read  a little lower, no the less better than would have been possible with props.

The setup was left and fingers crossed.

Later in the afternoon it was noted the vacuum gauge had dropped slightly, so the seal on the vacuum bag was revisited, after much stretching and pressing the vacuum was improved as shown below.

That’s about as good as it gets, bust a pity it was in place while the epoxy was wet, hey ho.  The pump has been on for about 6 hours so it will soon be time to leave it, and then tomorrow try and peel all the layers off to see how the panel looks !

Another very hot day, and the prospect of driving to Grimsby and spending time in the hole, was not a great.  We arrived late afternoon, it was dry, not too hot, so yes the hole beckoned.  The area for the patch was wiped with acetone, a table set up for mixing, and the vacuum pump made ready. The resin mixed, the area ‘wetted out with resin’, 3 layers of laminate added and  also wetted out.  The vacuum sandwich offered up against the laminate, and switched on.   The mastic tape pressed against the surface and the signs of a vacuum presented.  My gosh, could this be working:

In fact it was working too well as there were signs of resin in the breather layer already, so the vacuum was turned down:

All the preparation seems to have come together for a very tiny step in moving forward.  Does it matter if the patch has slipped under that vacuum, no not really, will just have to grind it out again … so what,  the achievement of laminating upside down with a vacuum is worth a drink to-night ….. yes please just note that was laminating upside down for the first time, and the first time of using a vacuum pump in earnest.

Most of the day has been spent preparing the patch material, the plan being to have a go at vacuum pressing that to achieve a thinner and stronger patch.

Shown below is a close-up of the bevel edge on the corner pads and holes which have been filled with epoxy filler.  The final hole will be smaller, and thus the hole will be surrounded by epoxy, so if there is a leak it will not have an easy path to the plywood.

The last few days have mainly concentrated on making the final corner pads out of marine ply, bevelling the edges and then gluing an identical bevel made out of balsa,  this essentially to negate a hard edge.

Yesterday another vacuum sandwich was prepared and we arrived back at the boat in the evening.

Today another dry run was attempted with the vacuum – to start with things went badly, with the layers of the sandwich slipping all over the place.   This was addressed with double sided tape between each layer – and success, a – .8 bar reading was obtained on the gauge – this being a new gauge with a separate breather unit placed away from the breather unit connected to the pump, this was evidence that a uniform vacuum was now achieved.

Good news is always followed by a challenge,  there was hissing, the tape was checked and other seals but the noise persisted.  The vacuum was that darned good it was pulling air through the chip in the fibreglass.   A piece of tape over the chip negated the hissing and the vacuum gauge moved past 0.8 bar.  First thoughts turned to just letting this fill with epoxy when the live run was done where the balsa will be coated with epoxy filler.  However, if that epoxy filler pulled through to the surface, then the new polyester gel-coat would not adhere to the epoxy.  Whilst the vacuum was still in place some polyester filler was used from the outer surface.  After the vacuum was released it was clear that the filler had pulled through quite nicely – however, now did not seem like the time to take short-cuts as that’s what got us into this mess in the first place.  Therefore a disc grinder was used to grind a bevel round the compromised area,  the plan being to patch it properly before attempting to epoxy the balsa panel in place.

Some final sizing was done on the corner pads and the necessary holes were drilled, but after that we had to return home again to get some fibreglass cloth and resin. So this evening the task has been to fill the holes in the pads and balsa panel with epoxy to ensure there is no exposed wood when the final holes are drilled for the bolts – a picture should explain better, but the glue is wet presently –  and the garage door has been locked to avoid the temptation of seeing how the glue is setting 🙂

Today’s entry started at about 04.30 am, only to find there was a restriction on file size uploads and whilst trouble shooting the USB disc for the raspberry pi failed, oh joys.   Fortunately I had created a spare disc ready to plug in, and was able to upload the backups for WordPress.  Of course being on the spare USB disc means a back up file needed to created for that as well ….. enough said hours of work.

Yes,  vacuum bagging at the weekend, well the dry run upside down was about as challenging as one might have expected.  The sticky mastic tape,  does adhere after a fashion to fibreglass but it was tricky, then came the moment of lifting the panel and various materials … oops it slipped slightly and the vacuum bag plastic caught on the mastic tape and it had no intention of coming free and tore the vacuum film.

Of course challenges had been anticipated and a spare had been prepared earlier, more care, and it slipped again …. the air was colourful and the Crew kept very quiet.   So the vacuum plastic was hanging down and the sandwich removed – doom and failure.  With a little patience it was possible to reseal the vacuum material against the mastic and some success ……….

The pump was working and the regulator confirmed a vacuum.

With the new confidence, it was possible to peel the tape from the fibreglass and have a go with the panel and a small piece of beather fabric.

Even with the breather fabric the vacuum did not appear to be equal over the area, which needed investigation.  Further reading identified the likely problem, namely the fact the breather fabric needs to be over the whole area.  Additionally a vacuum gauge has been purchased along with another breach to confirm a vacuum at another point.

The prospect of manipulating the balsa panel with a layer of epoxy on it is daunting, and so further thought was given as to how this might be achieved.

Some means of wedging the panel giving time to make the seals is going to be essential.

Flexed plastic piping may be the way forward and some redesign of the plywood panel supporting it …. more thought required.

The plywood pads were also sized over the weekend.

We returned home Sunday, and yesterday and the bevels were cut in the balsa panel, and the bevelled pads were made.

The edges of the other other plywood pads were also bevelled, and some balsa is being glued against those edges.

The plan for the weekend ahead is more vacuum practice, and then the trauma of doing it for real !

Much planning and thinking today, two trial chamfered discs prepared to see if they will lie flat on the curve of the transom.  The balsa insert cut and shaped roughly to size.  The plan being to finish trimming at the boat over the weekend, mark the location of the bolt holes for the chamfered discs, so a cut out can be made in the right place.

The big feature for the weekend, weather permitting, is the dry run on a vacuum setup.  The photograph below shows initial preparations. The balsa insert lies on top of a breather material which soaks up excess resin, below that is the plastic film that forms a vacuum against the surrounding fiberglass in the transom.  In the final sandwich there are two other layers – more of those later.

The photograph below the balsa and breather material have been removed to show the plastic film and breach unit in situ.

A cut out in the plywood template allows the breach unit to be assembled and supported, the plan being simply to lift the plywood, with the balsa et al, into the cut in the transom.  This, with some luck, can be wedged holding it all in place whilst a seal can be effected between the plastic sheet and the transom – the pump can be connected and switched on.  Well that’s the plan.

Mmmm, having written the blog entry,  its clear of another challenge, assuming the vacuum is successful, the plywood will come away but can’t be removed from the pipe which will lead to the breach unit from the pump.   It will either have to be supported lower down, or lightly wedged back up against the sandwich, once satisfied all is well.

Returned home to take advantage of cover, routing table, and band-saw etc. The cardboard templates have been used to make more robust templates on thin plywood. Shown below is the larger template along with a sample of end grain balsa.  This being the challenge not mentioned in the books that end grain balsa does not support its-self and simply folds over as the picture shows.  Of course this is not a problem when working with gravity on a mould, but upside down this could be tricky.

Plan B, a layer of 450g chop strand mat (CMS) was glassed to the surface of a piece of balsa larger that the plywood template, which seems to have given it some support whilst retaining the ability to flex.

Ultimately there is to be two circular marine ply pads inserted into the balsa, so that the pads on the stainless steel poles clamp onto solid ply and not balsa – this potentially being an improvement to when the boat was new.   If these could simply be circular pieces of ply then this wold be straight forward, however, as the experts out there will know you should not create hard edges against fibreglass or it may stress and crack – not good.   So the edge of the ply needs to be chamfered, and with that of course so does the balsa into which it is inserted.   The dust cover from the routing table has been removed and setup.

Whilst tempting to do this from the cardboard template, some thought will be given as to whether to do a final fit on the plywood template and check the locating holes etc.  This will also give a chance to do a dummy run on setting up a vacuum to hold it all in place – who in their right mind would do their first vacuum layup – upside down – needs must.  Yes the initial layer of CSM could have been done as a vacuum layup on the balsa but that might / would have forced the resin into the kerfs in the balsa which would have made it solid.

Some time spent at home ordering materials, vacuum pump equipment etc.  Returned to the boat yesterday, and today continued preparation including making cardboard templates for the smaller cut outs on the port and starboard side.

Next step will be to make plywood templates, and hopefully use these to make marine ply backing plates instead of the balsa core.

The plan is still to use epoxy resin to glue the final balsa and marine ply core, however, it is likely that a polyester resin will be used to replace the inner laminate.  The first reason for this is, apparently if you undertake a repair with different material to the original it can invalidate you insurance unless approved by a marine surveyor.  Secondly epoxy resin layup can be brittle, where as polyester layup has more flex.  The transom does flex with the wind generator running.