Hard Top II

//Hard Top II

Hard Top II

(Photos HT-001, HT-002)

Have you ever suffered from “Where the hell is that Fl.G.2s?”or “Is that red light moving off the port bow?” and “is the angle changing?
On a night passage one of my biggest dislikes is peering forward through wobbly, opaque plastic windows, having to stick my head out into the elements every few minutes to try and pacify my increasing paranoia.

I found myself looking longingly at Hallberg Rassy’s, Najad’s and even the occasional Bavaria thinking maybe I could make something to fit my mid 80’s ¾ tonner.
I looked about on the internet at after-market examples and frankly nothing really looked like it would work on my boat.

Apart from the improved visibility I had a number of additional provisos that the design needed meet.
1. Standing at the helm I need to be able to see the bow.
2. Without a raised cockpit combing the bottom of the hard-top needed to extend well aft of the coachroof to deflect water running down the windward sidedeck.
3. There had to be enough clearance for the main winch handles, good access to clutches etc.
4. Long and strong enough to take the weight of 2 x 100w solar panels.
5. The canvas top needs to fold down easily.
6. The design needs to match the overall style of the boat.

(Photos HT-003, HT-004, HT-006)

I took a number of photos of the boat, printed them out and then drew what I wanted which at least gave me an idea of angles of the windows.
With these ideas in mind I cut some panels out of scrap plywood and taped them in position with masking tape.

I took photos, walked away and looked from distance from various angles and concluded that mk1 plywood mock-up wasn’t big enough.
However I had at least found a process that would work.

(Photos HT-007, HT-008, HT-009)

Mk2 was better and I adjusted various angles and re-taped a number of times.
I checked winch handle clearance, looked over the top from my normal, tiller between the knees entering leaving harbour position and carried on adjusting the position of each panel until I was happy.

I had only templated the centre and port side so I dismantled the panels and reassembled them to check the starboard side was the same and give or take a few mm it was the same.
Not something you can guarantee, especially on boats built in the 80’s.

(Photos HT-010, HT-011, HT-012)

I replicated the 9 plywood panels in some offcuts of shower-board. I could have used anything which had a nice shiny surface like melamine faced ply or even chipboard.

This time I assembled the structure using resin tape on the joints, though parcel tape would have worked just as well.
Each joint was glued using a hot glue gun and I added stiffening to the larger front panel.
At this point I also added a 40mm wide flange around the top edge which would act to stiffen the whole structure.
As the outer surface would end up being the visible inside of the hardtop, I waxed and polished so when the time came the board would part easily from the glass fibre.

(Photos HT013, HT-014)

I checked on the weather as I needed a full day without the prospect of rain.
I applied three coats of white gelcoat.
The outside temp was around 14deg so it took around an hour between each coat, even though I’d been quite generous with the catalyst.
I find that csm has a better bond to gelcoat than woven cloth so after lunch I applied an initial layer of 250g chopped strand mat (csm).
This was followed by three layers of 250g biaxial cloth.

I taped up a strip around 2” wide, internally around the deck where the hard top will land and using 4” wide plain weave tape, glassed a flange all the way round.
This provided a perfectly matched base between the hardtop and deck.

(Photos HT019, HT-020, HT-021)

After a few days I lifted the whole assembly off the boat and trimmed the edges and sanded the outer surface down with a course grit paper and then removed all the dust to provide a good key for the next stage.

I needed the structure to be stiff but at the same time I wanted to avoid too much weight.
The obvious solution was to use Carbon fibre.

Contrary to popular belief its perfectly possible to use Carbon fibre with polyester resin.
Admittedly its not as good as using epoxy resin but its still very good.

I used a plain weave, 100mm wide, 240g carbon fibre tape which at less than £5 a meter won’t break the bank.
In the high stress areas I applied four layers of carbon followed by a couple more layers of normal 300g biaxial.

(Photos HT-023)

After the glass had cured to the touch I trimmed all the excess and gave the outside a good sand to provide a flat surface and a key for outer layers of gelcoat.
I applied three thin coats of normal gelcoat followed by a final coat of gelcoat with added wax in styrene, added roughly in the same quantity as the catalyst. Otherwise known as topcoat gelcoat or flowcoat.
Its important when coating gelcoat to use multiple thin coats rather than a couple of thick coats otherwise there is a strong chance you will trap small air bubbles which when sanding back will appear and they are a real pain to get rid of.

Normal gelcoat will not “go off” unless you remove the oxygen. The idea of the wax additive is that during the curing process the wax comes to the surface sealing off the gelcoat from the air.
It’s worth using a roller for the top coat or even a good quality brush as the flatter you get this final coat the less sanding is required.

(Photos HT024, HT-025, HT-026)

To understand how to get a nice shiny finish you need to work backwards in the process.
The final shining process is using a cutting paste and buffing.
Cutting paste will take out 1000 or 1500 grit scratches.
1000grit wet and dry will take out 320 or 400 grit orbital sander scratches.
320grit dry paper will remove 180 or 240grit orbital sander scratches.

So my usual process is firstly scribble all over the surface using a permanent marker and sand this off using 240grit paper.
The scribble allows you clearly see the highs and lows in the surface of the gelcoat.
This technique is repeated using 400grit and then 1500grit and finally cutting with a suitable cutting paste.

(Photos HT-027, HT-028, HT-029, HT-030, HT-031, HT-032)

The hardtop was then moved back to the boat for a test fit.
After the addition of the carbon and other glass plus the gelcoat I needed to be sure the structure had not twisted or moved about too much before the windows were fitted.
This pretty much the last opportunity to make adjustments as after the windows are fitted it would become far more difficult.

(Photos HT-033)

My initial plan was to use toughened glass for the windows but the cost was pretty high especially on an unproven project, plus due to the weight of the glass I’d have the added complication of adding an internal flange to hold the glass in place.

So I opted to use the much lighter 8mm Acryglas, although any of the acrylic glass materials would have been fine.

I cut each one out using a jigsaw with a fine metal blade and then, as the edges will be visible inside, I sanded the edges with 240grit paper to get the jigsaw scratches out and then with 500 then 1000 grit wet and dry.

(Photos HT-034, HT-035)

The window panels were cut leaving a 30mm overlap all the way round.
This strip was taped off and I sanded the mating area using 80grit paper to provide a good key.
I used white Sabatack 750 to bond the windows in place and clamping them for 24 hours.

(Photos HT-036, HT-038, HT-040)

I bought a couple of lengths of 15mm diameter copper tube and having decided on suitable pivot positions bent the tube to support the canvas top.
Once I was happy with the copper tube which is very easy to bend I copied each frame using 20mm 316 stainless steel though I did consider using aluminium.

I’d previously bought some waterproof cordura type canvas and had a largish off cut so having taped the frames into the correct position I draped the material over and again using tape and some ss screws manoeuvred, cut, tweaked the canvas into position and by total surprise I found that apart from a couple of pleats I didn’t have to make panels.

Now I can feel you cover makers wincing here at my rather amateurish attempts at cover making but this was a Wednesday and we were sailing to Holland on the Saturday so needs must.
However after an evening sewing hems and webbing to stress areas, velcro to hold everything in place, it all came together pretty well, plus is was £600 cheaper than I’d been quoted!

I bonded down the hardtop to the deck using Sabatack and this was weighted down for 24 hours.
I gave the whole structure a dammed great tug about and concluded that I didn’t need any through bolts which pleases me no end as I hate with a passion drilling holes in my deck.

(Photo HT-041)

Its been across the pond a couple of times, had a couple of green water hits as we’ve rounded Orford Ness in a blow.
Has seen off the winter storms on her rather exposed mooring and still has not attracted the ire of SWMBO which in our house is 90% of the battle, though we’ve had words on the sailcover, dodgers and now sprayhood being three different colours.

Overall the hardtop has done exactly what I wanted and worked really well on the two night passages I’ve made with it.
In fact we now have a new prime location when its cold and wet, which is sitting in the companion way entrance, on a cushion looking out through the windows, cosy as a bug in rug.

2020-06-09T20:40:14+01:00