Structural parts, Uni directional glass

Laying Uni’s.

Posted by Paul

I was at the shed for 7 hours today, but I spent nearly 2 hours of that time chatting to visitors. One of the great things about building a cat like this (and publicly on the website) is that there are many interested in what I am doing and the catamaran community is without doubt the friendliest bunch of people around. Take yesterday for example. I stopped to watch the cat above being loaded onto the truck and after less than 5 minutes chatting to the owner and explaining my interest he had offered me a sail on his cat as soon as he gets it back in the water. Amazing! He only knew me for 5 minutes! Today Amnon and his brother Sam, both contemplating building a cat (together) visited for a run down on what is involved in building a cat and my progress to date. After going over the build so far and my plans for how and what I am doing, I told them they must attend the next Schionning muster in October to see finished cats on the water. Along with visiting works in progress, seeing finished boats is a must see for anyone thinking of building.

So when I eventually did get to work I set about laying down the uni tapes to the back of Bulkhead 4 (the front of the bedrooms). I suspect I am going to have to cut holes in the webs forward of this bulkhead in the curved section to lay uni tapes there too but I will leave that until last. If I do have to do that I will also lay a conduit down to take the water pipes for the forward ensuite in the sb hull before gluing the cut-out pieces back in. It would have been much easier to cut these sections out before gluing the deck up but no big deal. It may not even be necessary, I still have to confirm with the designers.

I mixed up pots of 400g of ADR resin and pots of 100g of ADR hardener and used a third pot to pour into and mix. If you use 3 pots this way you can use 1 for each of the parts and have a texta mark on the side for a rough idea and then as you weigh them you can add or subtract back into the main drums until correct weight and then use the third pot to pour them into to mix, and then you can always have the next pots full and ready to mix. The stuff doesn’t start to go off until you mix them, so this way you are always ready with the next pot as you may run out half way through a tape. (This resin is also know as kinetics and has a much longer pot life than West so you are not under the same time pressure so this readiness is not as critical but still a handy habit to be in because in summer you definitely don’t have time to waste).

I laid down 4 uni tapes each shorter by about 300mm each end than the one below it with the longest on the bottom. I rolled the uni’s up and then unrolled them laying them out dry on the bridgedeck. I placed the first right up against the bulkhead and once it was centred I wet it out starting at the centre and working out to the ends. With each subsequent tape I unrolled them about 200mm behind the bulkhead, then I placed the tape a little at a time into place over the wet tape below and again starting from the middle out to each side and down into the hull I wet the tape out using a brush and a tub of resin. I repeated this until all 4 tapes were down and wet.

I then mixed up some coving material and coved the bridgedeck to bulkhead angle over the uni tapes. I didn’t have to do this in the hulls as these had already been coved when I taped the bulkheads into the hulls, I just had to blend the deck cove into the hull coves for a smooth transition. I then used the wombat and West resin to wet out a 200mm tape and covered over the uni’s with a final double bi tape and then I covered it all with peel ply. Most of these tapes will be completely covered by furniture with only small sections visible so I used recycled peel ply. A tip here is that it is much easier to lay peel ply in flat sections and to cut the peel ply and start again on the next angle than trying to make peel ply go around corners.

Because the ADR is mixed by weight 4:1 I know exactly how much resin I used. I used 4 lots of 500g of resin. Each full length (7500mm) x 60mm at 1000g per square meter means that each full length of tape weighed about 450g. Each tape was about 600mm shorter than the tape before and I had about a quarter of a tub or 120g of resin left when finished. So I think I can say I used close enough to 1:1 resin on the uni’s. I also used 12 pumps of resin (each pump is 50g) or 600g to wet out a 7500mm x 200mm 457g double bi tape, this works out to 685 grams of tape, and I used up the last of the ADR (It still hadn’t gone off!) so about 700g of resin give or take for 685 grams of tape, again, as close as spit to 1:1. I am pretty chuffed that without consciously trying I am getting an almost perfect resin to glass ratio.

No pictures today because I was too busy getting the job done after wasting time early. It took me 5 hours to lay the 5 tapes but I figure I will get much faster now that I have done 1 set. I may even be able to get double that much done in the same time next time. Either both sides of a similar layout or one of the 7 layer layouts. I will stop for photos next time.

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