Monday, August 30, 2010

Just weighted the hull.

currently at 35 kgs that includes:

  • Hull
  • Floor glued and laminated in
  • 1 side tank
  • Bulkheads
  • bowsprit structure
  • transom bar
  • Gantry
  • Carbon blocks for fittings (almost 0.5 kg)
The class minimum weight is 51kgs including control lines and bowsprit.

So i figure 5 kg more in glue and fibreglass, 3-4 kg more in fairing compound and primer allowing 7 kg for fittings, bolts, ropes and foot loops.

So at this stage its looking like i should be able to fetch the minimum weight with not too much hassle unless the hull requires a lot more filler than first thought or paint.

Sunday, August 29, 2010

Current progress

This is the side tank under vacuum on the side tank mould. I was quite happy with how this process worked. Using only 5 supporting frames and a 3mm sheet of melamine coated MDF as the mould surface the shape held very well, even under vacuum there was no distortion or warping.
This is a roughly trimmed side tank, this will be going on the port side and will house the spinnaker to keep the cockpit neat and tidy. The mould gave a good smooth surface which should be easy to paint straight to will minimal filling and sanding.

This is the "tension member" that I have Incorporated into the hull fit out. The idea behind it is to help triangulate or form a space frame between the mast step and stay mounts to help increase the stiffness of the hull and rig, which hopefully will help to reduce fore stay sag when sailing, which may ultimately allow for a wider range of rig tensions to be used. The member only weighted 280g so hopefully the advantage will be worth the small weight penalty.

This is a quick image of the fore stay mount attached to the top of the bowsprit receiving tube. The plate is made from two layers of 2mm thick 0/90 deg woven prep reg plate, then extra layers of 0 deg fibres to deal with the tensile load and +- 45 deg fibre to resist "shear out" of the fore stay pin

This is a photo of the rear bulkhead that supports the bowsprit receiver tube. The bulkhead is glass and foam with local carbon reinforcement to help distribute the load to the hull. The joining tape for the bulkhead to hull joint is laid on the -+ 45 deg to provide good shear strength in the joint.
The floor has finally been glued into place using Q-cells and epoxy.

The centreboard case was opened up and the polystyrene foam was dug out.

This is a photo to try and show the collapse that we found in out rudder. That surface was the upward facing surface in our mould when we used to expanding epoxy foam. It looks at this stage like it was a large air pocket or void which has collapsed for some reason after it was made. Although we are uncertain why it collapsed as the carbon skin should want to stay in its moulded shape so they must be some sort of suction or residual stress present to force it to collapse, time will tell...

Also completed but i don't have any photos at this stage, the port side tank has been fitted, starboard side tank has been laminated, rudder gantry fitted and trimmed, spinnaker opening shaped, spinnaker chute has been laminated and carbon plates for fittings have been cut.

Bring you more photos shortly.

Thursday, August 19, 2010

Quick update

Above are a few images of the new side tank moulds. They were made using five 16mm MDF templates glued to backing strips then a sheet of 3mm melamine coated MDF was bent over the frames and glued down. Hopefully this set up will be able to resist the loads put on it from the vacuum bag, only one way to find out i guess. Plan is to pop one of these out this weekend.

Above is an image of us doing a rough fit / check of the foredeck and floor panels. Both of the these were pulled straight from the CAD model and fitted really well straight away. The foredeck template was also useful in highlighting how much the hull actually moved / spread out once it was removed from the jig.

This is a photo of the bowsprit receiver tube that i thought would be useful to share. Basically to fit the receiver tube a section was cut out of the bow and a simple bulkhead with a hole cut in it was made to support the back. The section that is on the stem will have a fairly substantial laminate (3-4 layers of 300gsm UNI + 1x 200gsm cloth) wrapping over it and down both sides of the bow. The bulkhead will then have a few strips of uni and some cloth to take to load to the gunwales and down lower on the sides of the hull. This area is going to have a few more little tricky bits and ideas thrown at it over the next couple of weeks so I'll keep you updated.

Tuesday, August 10, 2010

Floor ribs laminated in, centreboard case laminated in, bulkheads laminated in.

Next on the list:
  • Fitting bowsprit snout
  • Fitting floor
  • and building side tank moulds
I'll through some photos up shortly

Saturday, August 7, 2010

quick update of todays work:

Bulkheads glued in
Floor ribs glued in
Centreboard case glued in

Plan for tomorrow,
Laminate in place all of the above and trim/fit floor and mast step area.

Tuesday, August 3, 2010

mucking around with paint schemes

current thinking is red hull/deck/side tanks with white floor, carbon fibre finish on; transom bar, gantry, rudder box, foot rests. Then black gunwhale and fore deck grip. P.s. i'm also open to suggestions for paint schemes and names.


Over the past week we have been a little busy. Firstly we finished making the mouldings for the dolly, took the hull off the jig, laminated the inside, began fitting internal ribs.
We made the dolly last year after undertaking a basic TIG welding course at TAFE one night a week for a semester. As our final project we made the dolly for the cherub using 60x40x3 6061-T6 aluminium and used 25x1.5mm 316 stainless steel for the axles. All up in materials i think it cost about $200 plus $40 for wheels from eBay. So to fit it to the new boat all we needed to do was make a support for the hull. Note: The reason we used such heavy section aluminium was because of the way our boat sits on our 8x4 ft box trailer.

The above image is the centreboard case as it came out of the vacuum bag as you can see it pulled into the corners quite nicely and the overall finish is pretty good. The second image is the Styrofoam beginning to be melted out with acetone, after beginning this i realised it would have been a much better idea to leave to foam in there until it was in the hull as it is quite flimsy, so i stopped. Although i did notice that acetone was able to seep from the inside to the outside of the skin even though there was 4 layers of 200gsm glass, so it looks like i will need to paint the outside with a coat of resin to help make it water tight after it is in the boat.

I thought this image was worth adding this is the size of the extra reinforcing patch i used under the mast this was 1 200gsm carbon cloth on the 0/90 degree angle to the centre line (compared the the main hull skin at -+45)

I thought this was a good image to add showing the laminate wrapping around the hull/chine. Overall i was pretty happy with how the -+45 laminate laid over the hull and continued to stay approximately at -+45 as we worked towards the bow. I guess I'll see how good that decision was when we come to trying to fair the hull.

The first image is the jig again once once the hull was removed, the second showing how it was able to flat pack and store easily (to dismantle the jig only took 15mins and a electric screw driver)

This image is of the legs of the table/jig, i thought it was worth mentioning how we levelled the jig. Because our jig design had a table with 5 legs it was important to have the leg length adjustable to account for the un-even floor of the garage and our assembly etc. So we used a "coach- screw" in the bottom of each leg allowing the height to be adjusted simply with an open ended spanner.

This is the hull as it can off the jig.

This is the hull after we laminated the inside of the hull, same lay-up as the outside as it is very important to try and keep the laminated balanced so that when the hull is loaded up it doesn't try to warp. Also the floor ribs have been trimmed and ready to glue in and the centreboard case has been roughly fitted.

These are foils after we sanded the recess on the leading edges ready for their joining tape (1x 200gsm layer at -+ 45 to the centre line so it drapes well over the corner the fibres are at the right angle to resist the shear loads at the join)