As I mentioned in a previous post I want to put some detail into the cabin and in order to do this I wanted the roof to open so that the detail can be seen and also giving good access for construction and detailing. So I looked at various lifting lever systems and the one which gave greatest access and took minimal room was a simple parallel bar mechanism. I first made a card model to ensure it worked before investing a lot of work in making the real thing. I used some brass plate cut into 3 x 2mm strips and using 10BA fastenings I constructed the levers and securing plates. Before fitting the mechanism and cutting any roof trusses I tried the mechanism using the brass bars and a card roof replica to once again prove its operation. I then added further cross beams to ensure the roof frame stays stable when the roof is lifted and that the roof skins had sufficient support when closed. All through this design and make session the cabin frame was only secured by temporary pins and had and no roof skins fitted, this enabled it to be lifted off in one piece whilst working on the frame. Now the mechanism works the cabin detail can be finished before finally fitting the roof skins.

Now the cabin roof mechanism is working I have to finish all the detail in the cabin before I effectively seal the cabin with window frames and roof skins. However I thought I would check the fitting of the windows and roof skins just as a change from detailing. Because the roof is now movable it means the roof skins will need additional support. Also the windows as given were short in terms of height and the roof skins only fitted where they touched and both would need some remodelling/remaking. I decided to remake the windows out of 1.5 mm ply instead of the 1mm supplied in the kit and resize the overall dimensions and then slightly reposition the window openings. The 1.5mm will also accept the plastic windows within the opening instead of being just stuck to the inside. I forgot to mention that the front deck needs fitting before the cabin construction starts as the porthole pieces sit on top of the deck

Having sorted the windows out, they can now wait until the detailing is finished before final fitting. The roof skins are all compound curves so they will need to be steamed and formed before fitting as they will definitely have to hold their shape as there isn’t as much to fasten them to in terms of framework. After final fitting I will glass both inner and outer faces which will ensure the shape is retained and also help strengthen them to withstand any bumps /knocks during its lifetime. I made formers out of some softwood to match each of the roof profiles. Each piece was then soaked in hot water for around 5 mins and then clamped on the formers and left to dry for a day or so.

Having remade all the front cabin window frames I then decided to fit the acrylics into the opening (nice tight fit) all done! Or maybe not, someone then said how about “opening windows” it’s been done before. So would opening windows be a problem with water ingress? And would putting foam seals solve this problem? I’m not convinced. Having given the problem some days thought, how about going with the windows as planned which are now 1.5mm thick and inset into the surround. Then fitting an over window frame 1.0mm ply/plasticard with another thinner (1.0mm) acrylic window and hinging this above each window. This would solve the issue of water ingress and also give the appearance of opening front windows. Looking at how one other person approached this, it looks like the hinge was a brass tube across the majority of the window top and then a shorter piece the same dia tube at each end with an internal wire for rotation these short pieces are then fitted to the body of the inner window frame. These additional window frames can be added at a later stage and this doesn’t hinder the final finishing of the roof skins. So final fitting and adjustment and then pin and clamp in position the forward roof skins. When these are dry the window frames can be finally trimmed and then pinned into position and checked for fit then removed and then to each one apply the aliphatic glue and fit –pin and clamp in position

Now that the internal detail of the cabin has been finalised and fixing points made for each of the panels and floor pieces (all parts of the cabin detail are to be removable) I can now finally fit the cabin roof skins. Since the leading edge has an overhang which because of the lifting design hasn’t the same framework support I have decided to reinforce the joint with stainless steel pins.to ensure a perfect fit, I made a tiny jig out of brass angle that ensured all the holes in each piece lined up. I then placed pieces of silicon sheet on the parts I really didn’t want the skins to stick to the cabin framework. Fist all the pieces were position and pinned to ensure a good fit, they were then removed adhesive applied and the skins finally placed and pinned, most of the pins will be removed when it’s dry. The centre panel has an opening for the hatch so this was put in prior to fixing. After a day’s drying it’s time to see if the whole thing works as envisaged, thankfully it does. The roof will now have to be dismantled so further work can be carried out it, will also get a covering of glass matting to add overall strength.

I purchased as recommended by Robbob the fibreglass package which consisted of 750g of epoxy resin and 250g of hardener, I also went for the 90min cure as this is the first time I have ever done a boat hull, I’ve done plenty of stranded fibre cowlings/air intakes etc. where you lay a gel coat first then stranded matting which is so different to laying a fine matt on its own. I also ordered some mixing sticks and throw away brushes. First I cut the matting to the slightly oversize for one of the side skins, then loosely taped the matt to the bottom skin and checked the coverage - and checked again then fold over to the opposite side, this then leaves the surface clear to apply the resin. Mixing the resin should be done accurately, so borrow the kitchen scales and here we go. I wasn’t sure how much to mix for a side skin but 25g of resin and 7.5g of hardener looks about right. So mix well and then brush onto the side skin, then I gently lifted over the matting and laid it on the skin and gently brushed the matting down, the matting is almost sucked onto the resin so minimal brushing is required to ensure a smooth surface A previous blog said that “Less is More” how true this is, the temptation to spread the remainder of the resin on to the already adhered matt is something to be avoided, however learn by my mistake as I did just that (only in a small area on one skin) leaving rather a lot of sanding later after the resin had fully cured as it leaves a rather lumpy surface. So onward and upwards the following three surfaces were relatively easy with only minor difficulty keeping the matting in close to the 90 degree angle between the keel and skin and I had to keep going back to it pressing it in with a steel rule until the resin started to go off but minimal resin left a surface that was flat and the weave of the glass matt can be clearly seen and felt but minimal sanding is required if at all. Then a further 2 coats of resin with sanding in between will leave a smooth surface ready for final preparation of painting. The final picture is of the roof that in a previous page I said to add strength the roof would need a coat of glass to reinforce the unsupported edges –
To be continued

Before I do the final coats of epoxy the rubbing stakes need to be fitted but then Robbob pointed out the vulnerability of the bow particularly when transporting through doorways. I decided to take that advice and make a brass bow bumper, this will not be visible when finished but will stop any structural damage if the bow is hit, it was screwed and epoxied in position. The design also incorporates a location for the rubbing strakes holding them in position when fitting.
Thanks Robbob

Gunwhale rubbing strakes
As these pieces will be under stress they need to be steamed into shape prior to fitting so out with the wallpaper stripper and modified tube (1/4 BSP fitting in the bottom of an old piece of IKEA cloths rail).For the gunwhale strakes I used the same former as I used for the stringers so 20 mins in the steamer then into the jig for 2 days drying. The chine rubbing strakes will need a different jig but this time a left and right hand version as not only do they bend round but also up at the bow. I was however disappointed with the quality of the 3/16 square obeche as the grain was nearly at 45 degrees to its length – it snapped before I started to bend it, just pushing it into the jig I bought some better pieces from the local model shop.
I temporally fitted the gunwhale rubbing strake slightly proud of the deck level in order to drill all the pin holes then remove and mix up some epoxy, coat the length and hook into the brass bow and start tapping in the pins along the length of the boat, repeat on the port side.
Chine rubbing strakes are still in the jig!

Since I had been finishing the Gunwhale rubbing strakes and had the boat right side up and I was going on holiday for a few days I decide to glass the deck this would give the deck time to set. So some fine filling and then cut the matting to shape. Again I put a light coat of resin onto the deck then allowed the matting to sink into the resin, a minimal amount of brushing is required and then its left to harden overnight. The resin is now sufficiently hardened after two days so before I go away I can apply another light coat of resin which fills the matting pattern very easily - a week away now will allow the resin to harden fully.

As the hull glass matting is really dry and has had some minor filling done it’s time to fit the chine rubbing strakes. which have been in the jig now for some days and consisted of a two dimensional curvature jig. in order to make sure the strakes were equally balanced on each side I made a cardboard template that followed the Chine stringers line and rested on the Gunwhale rubbing strakes, having drawn a line on the port side I flipped the template over and drew a line on the starboard side giving a perfectly equal curve on each side So now to prepare them for fitting. The jig had made a curve that was a really good fit without much spring. I decided to use some very small brass pins (0.5dia x 10mm long) to hold them whilst the epoxy sets. I pre drilled the whole length of the strake and lightly inserted pins along its length, then applied the epoxy and started to fix from the bow and followed the pencil line back to the stern. This was repeated on the other side, when set there was some minor filling to be done/filling pin holes.