Building A GRP Fly Bridge
start you should know that since I have built mine, I have asked myself this
question - would I do this again? I still have parts of the mould and I have
learnt lots of tricks so the answer is YES but be warned it is a big job. If
I didn’t have the time I would purchase something second-hand that was
similar to what I wanted and then modify it. Having said that I am very
pleased with the result here is a picture of my modified Shetland 570. I
have to admit it is a picture that I am very proud of.
As I was a
complete GRP novice I needed a book as a reference. Friends
would give me tips and information that I would forget. The best book that I
could find and would thoroughly recommend is (Blue Gee) Glassfibre and
Epoxy Wood Book (2nd Edition) by David Benoy (Bar Code
5027215889010). I sourced mine from Aladdins Cave Chandlery at Bursledon
Bridge, Hants. It cost me £20 but it had everything that I needed to know
and much more.
Designing the mould
From start to
finish the project took me a long time partly due to the unique shape that I
wanted. I had to decide on a good position for it on the boat, design it,
build it and then later (with a fishing season in between) completely
line-out with formica to enable the component moulding to release. It
actually took me a year! As it was to be positioned just forward of midships
I felt I needed a longer steeper V shape at the front. This would make the
overall look more acceptable too, matching existing lines of the bow and
giving a similar overall look of the Raider Boats, which I like the look of
but cost too much. This meant a bigger mould, more material and larger
windows. I wanted to be able to look around the Fly Bridge while steering
without obstruction. After taking a couple of side-on pictures and then
crudely editing those pictures I came up with something close to what I
thought would work.
Building the mould
proceeded to build the mould onto the boat to assume the lines and
dimensions that I preferred. Using 3mm plywood sheets and batons I
constructed the main mould, building the frame and sides first and then the
two front panels, and the roof. To give the moulding inherent strength you
need to add flanges with a radius to all edges. Due to the headroom I
required at 6’3” I decided to invert the back edge for two reasons; I did
not have to make the top 2” higher and any water should not run down my back
while steering. I also added a larger angled face in the middle of that
‘lip’ to be able to fit my fluorescent strip light.
Once this was
done I needed to make sure that I could lift off the mould and replace it
without it changing shape and prove that it would still fit when replaced. I
decided that the finished moulding should be bolted down through a flange
along the front edges and then as per the original screen that I removed,
bolt through the sides.
When I was
happy that I had the mould shaped reasonably right (not perfect) I lined it
with cheap white formica. I needed to take accurate templates of the sides
first so I used Laminate Wood Flooring 2 mm Foam Underlay to make the
templates, as it was large enough and very easy to cut and trim.
I used the
templates to mark the shapes onto the formica and then used a Black & Decker
‘nibbler’ attachment to an old Black & Decker drill that a colleague gave me
for cutting the formica to size. This could easily cut the shapes without
the formica ‘splitting off’. Using a good Stanley knife is probably better
on a straight cut. The formica is then stuck on with the proper contact
adhesive. After this the all the internal angles and corners are then formed
with a radius using plastercine. A radius tool gives the plasticine a smooth
uniform finish. Any rough edges were rubber down and taped with the 2”
packing tape. PLEASE DON’T DO THIS AND LEARN FROM MY MISTAKE. I had some bad
marks created in the Gelcoat by using the Packing Tape ‘trick’ when building
of the mould. Best avoid this and use fillers and rub down. There are no
interesting as the chandlery would not sell me the quantities that I needed
and the trade would not let me carry it in my car to my house. So I
purchased it all ‘on-line’ from
http://www.cfsnet.co.uk. It came on a lorry and was dropped off in my
drive while I was at work. Please note that I bought the ‘good stuff’ there
is the option of buying a lower standard product which for a budget flying
Bridge may be sensible option. There were no questions asked and no
problems. When I ordered a 5Kg can of Gelcoat or a 5Kg can Polyester Resin,
100g of Catalyst (Styrene) was sent free of charge (I suspect this worked
around some of the rules).
I won’t give
costs as you can find out very quickly on the above link but prices were
about 25% to 30% of the normal cost when compared to any of the chandlers
that I checked. For example 5kg of Clear Gelcoat was £22.40 plus VAT where
1Kg in the chandler’s shop was £17.99 including VAT!!!
a job similar to mine:
- About 3Kg of Clear Polyester Gelcoat for 2 coats (The text books
say 1M squared area = 500g of Gelcoat, which worked for me).|
Gelcoat Colour Pigment
- I needed about 200g so I had to buy a 500g can of pigment. To add
colour to 500g of Clear Gelcoat use 5% to 10% of the pigment. I always
used just over 5%. Therefore for 500g I used 30g (30cc) of pigment.|
300g M5 Chopped Strand Mat
= 10Kg. I probably used about 7Kg of the 10Kg roll. (450g CSM may
be a better option but I don’t know).|
rollers or 2” paint brushes.|
3 or 4
Mixing Sticks (mixing Gelcoat will make them soft, mixing resin does not).|
Graduated 1.2 ltr Buckets.|
Calibrated Measuring ‘Cups’ up to 30cc - for adding pigment and catalyst.|
– 1 ltr for cleaning equipment.|
Consolidating roller tool.|
or Marigold Gloves.|
** Try to
obtain a colour pigment that is close to what you want or choose a colour
contrast. You can aim to get an exact match but that will be your choice.
If you go for an exact match you must read the book referenced above to
learn how to do this. I went for a similar (near match) colour ‘Light
Note after the
first coat of Gel I noted the 2” Packing Tape had started to ‘pucker’- boy
was I pi**ed off. Hopefully as warned above you did not do a similar thing.
See pics below. I applied a thick second coating over these areas as I knew
I would be rubbing it down to get a better finish. This tidying of the
moulding took a lot of time.
Preparation Prevents PPPP Poor Performance!!
If like me,
you are a complete novice, I would do exactly what the reference book
advises. Simply follow the book and build 2 small projects. It gives you an
idea of just how good and easy it will be and gives some confidence that
what you are doing will actually work!
ideally in 15 -20 degrees C. Work in a well ventilated area. Use eye
protectors if working in any awkward positions. Read all material label
Gelcoating: This part took me 6 hours from start to
mould by wiping down with Acetone.|
mould well with at least 2 good coats of mould release wax onto formica,
you need more layers on other surfaces.|
Pour 500g of
Clear Gelcoat into a graduated pot.|
Mix in 30g
of pigment (just over 5%) and stir in well, particularly into the corners
of the pot.|
Mix in 10g
of Styrene/Catalyst (use 2% catalyst for Gelcoat) and stir in well;
particularly into the corners of the pot, it starts to cure from now!|
thick to all surfaces of the mould, slap it on!|
ENOUGH THAT YOU CAN USE IN 10 MINUTES! Hence 500g at a time.|
complete coat, leave for 2 hours to ‘Gel’.|
Allow to set
for 12 hours.|
‘Laying Up’ Preparation
For 300g CSM
(1oz) you will need 6 layers to make a 5mm thick moulding (6oz lay-up)!!!
For each Kg of CSM you lay you will need about 2Kg of Polyester Resin!!
the mixing pots that were used for mixing the Gelcoat it is thick stuff. Be
careful not to crack the mixing pot itself. They are now ready to use for
mixing the resin.
work can be a messy job if you are not prepared before you begin. I did the
lay-up part in sessions as it took much longer than I anticipated.
Cut all CSM
pieces to approximate size before starting to mix resin.
the resin at the end of the session I wiped the pots clean with Acetone.
Just get on with it ……. ‘Laying Up’
Mix 500g of
Polyester Resin with 5g of Styrene/catalyst and mix well. This is much
thinner than Gelcoat.|
Paint a good
coat onto the Gelcoat.|
Lay on the
cut pieces of CSM and roll flat with the consolidator roller.|
resin with a brush into the white areas and keep going until the surface
appears translucent with no white areas (indicating dry of resin or
Leave for 1
hour between layers, by the time I had finished on the first layer and had
coffee it was time to start the next.|
Lay up to 4
layers at anyone time (if you can) and then leave for 24 hours to cure.|
It is wise
to put strips of wood into larger areas to ‘stiffen’. It is the resultant
‘top hat’ profile of the mat laid across the strips of wood that actually
give the strength.|
I added the
wood strips after the first 2 layers of mat.|
I also added
2 pieces of conduit for cables to be fed down through from the mast, this
also added strength.|
6-7 layers to all sides with overlaps on all the corners. |
Before I did
this I trimmed the mould with a small angle grinder with a disk fitted meant
for stone blocks and floor tiles. Due to the amount of dust generated I
asked my daughter to Vacuum alongside the cutting edge to catch some of the
dust (we both wore gloves, face mask and goggles).
‘cracked out’ the moulding by working around the edges after removing most
of the batons used to stiffen the mould. I attempted to preserve the mould
but failed it was pretty much destroyed! I have kept the sides as they will
come in useful for something else yet I am sure. If not re-build into
another 570 Fly Bridge Mould.
At this point
I did a test fit on the boat and then removed it to finish off.
Finishing the Fly Bridge
holes to the ends of the built-in cable conduit.
Trim all sharp
corners of the flanges to give a good ‘seat’ for Titanfast trim.
‘spiky’ ends of glass and all the cut edges.
template for a window and when you are happy with size and position, mark
and cut out the holes for the windows. Note I did this after I had
already purchased the 5mm Clear Perspex/Acrylic off cut. This worked well as
they did not have the exact size that I needed but had an off cut very close
to what I wanted, so I compromised. It therefore became much cheaper to
purchase than a larger sheet (and with no waste).
fill any poor areas of Gelcoat, I had to do this due to the Packing Tape
that I used ‘puckering up’. Repairs should be fine as the mix is constant so
the colour should be identical (assume using same pigment), after a rubdown
and polish of the repaired area the repair should be undetectable.
Next use an
orbital sander to finish any other ‘poor’ areas of Gelcoat with 150 wet and
dry but finishing with 240, likely areas will be where plastercine was used
to give an internal radius to the mould.
Turn over and
paint the inside.
Gelcoat (easier to work on and would save some climbing around on the boat
while it was on the trailer).
Fitting the windows
I sourced the
Acrylic/Perspex sheet 5mm from ALDA PLASTICS, Unit G1, Liners
Freemantle, Southampton 023 8023 5423.
I then used a
rubber seal (part number BRS1123), buying 6M at £1.80/M, to fit the
Acrylic/Perspex windows sourced from Alexander Comrie & Son Ltd,
Second Avenue, Millbrook Road, Southampton 023 80702911.
There is a
knack with this. That is get the correct rubber i.e. one with the correct
gap for the material that fits into both slots. I struggled as I could not
source the correct rubber as one groove was correct at 4.5mm the other grove
just 1.5mm a bit tight but it still worked. Also the gap between the hole
and the Acrylic window has to be correct, in my c\ase about 5mm. It actually
took three of us to fit the first window. Then when we got the hang of it
just me and my wife Alison managed top fit the second window.
As I tried to
show here the filler needs to be fed into the grove and then pushed in using
a special ‘tool’. A Tool is available but I made mine from a wire boom after
a friend described it to me. One trick here was to push the ‘tool’ rather
than pull the ‘tool’.
Fitting stainless A Frame and mast
I cut down a
fitting that I previously purchased from Beaulieu Boat Jumble I then had a
stainless foot welded accros the bottom of both ends by Hythe Marine
Services who made a top job of the welding. It made sense to fit all this
while it was on the garage floor stillas this saved me some effort climbing
around the boat. I fitted the mast and fed the cables for the VHF Antenna,
Anchor light and Nav Light through the conduit.
Fitting to Boat
I finished all
edges with Black ‘Titanfast’ trim, buying10M at £1.95/M also sourced from
Alexander Comrie & Son Ltd, Second Avenue, Millbrook Road,
Southampton 023 80702911. Fitting was a three man job. Two had to
hold it inplace, as a certain amount of force enabled a better fit, while
the other drilled the holes. We bolted down through the front edge lip and
down through the cabin roof and screwed through bottom edge of the sides
ignoring original holes left by the original screen. I filled gaps with
silicon and bolted down tight. Last thing was to cut all the stainless bolt
ends off with an angle grinder. By bolting and keeping the old screen I
still have the option of swapping them back if I choose to sell her later.
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