Fibreglassing a Mast?

Hightower · 28 January 2008, 21:48

How would one go about making a mould for making a mast similar to the one in the sketch?

I would prefer to manufacter it in one piece if at all possible, however it would seem quite difficult to do fibreglass the smaller end.

Any thought?

jwalker · 28 January 2008, 21:55

Andy, is it open at the top? Are you making more than one?

Hightower · 28 January 2008, 22:02

It could be open at the top but was thinking of an enclosed structure. I might be making more than one. I first thought I'd like one big mast mounted in front of the Outboard, but while I like this design it interferes with deck space too much so was thinking of two smaller transom mounted ones that may or may not be joined together with an aerodynamic cross piece. Surface finish has to be spot on, which is why I was thinking of a mould.

Pete7 · 28 January 2008, 22:36

Andy I think to make that your going to have to lay up on the outside of a mould in a similar fashion to the way they make a fishing rod.

If your thinking of a T piece for the top then Osprey did try it on the early XR boats but the weak point was the GRP near the base kept breaking when the boat was driven hard.

Pete

jwalker · 28 January 2008, 22:37

OK. Firstly I'm presuming you're fully familiar with the wee red book so I'm ignoring the polishing and all the other necessaries.

1) You need to make one as a plug.
2) Put a rim up each side to form a flange. If the top is closed the flange should go right around the top also.
3) Laminate one side and onto the flange to form one side of the mould. Remove the rim and fettle then laminate the other side to form the second half of the mould.
4) Drill the flanges through to place clamping/locating bolts. Other location methods can be used too.
5) Split the two halves open to get your mould. Fettle as necessary.
6) Lay up one half into one side of the mould and trim accurately.
7) Lay up the second half and trim accurately. Bring the two halves together and locate/bolt together the flanges.
8) Join by prewetting strips of CSM laid on a flat stick, enter the stick into the moulding and flip it over to lay down the strip. Repeat as necessary and stipple down using a brush with the handle cut off screwed to a stick.

To improve the join, before you bring the two halves together it may be worth feathering out the edges to thin them and laying in some gelcoat as the first joining layer. This will leave you with a slightly ragged outside join edge of gel which you can work back to finish. Alternatively, you can lay a bead, between strips of masking tape, of contrasting flowcoat along the external joint line. It's the same method as used for joining a canoe hull to deck so you can look that up.

Hightower · 28 January 2008, 22:41

I wanted to keep away from an outside layup if at all possible as the surface finish is usually crap, but I understand the complexities of a mould layup. As for the strength I was going to incororate it into the transom and deck with a possible cross brace to two uprights.

Or might do as suggested to you earlier in the year and go for two stainless masts.

Hightower · 28 January 2008, 22:53

Thanks for that Jeff, I kind of discounted to two halfs method as I was unsure about the joining the two halfs together and was worried about the join mark I might get. But after reading your explanation it looks fairly straight forward.

I think what I'll do is to make the Mock up and place it on the RIB to see what it looks like. Then wait till the warmer weather

jwalker · 28 January 2008, 23:02

Quote:

Originally Posted by Hightower

I think what I'll do is to make the Mock up and place it on the RIB to see what it looks like.

Massive.

Quote:

Then wait till the warmer weather

Cop out.

Hightower · 28 January 2008, 23:08

So, our blood runs warm down here on the South Coast Jeff. We're not Ard as nails like you Scotts

B'sides don't fibreglassing like warmer temps....My excuse and I'm sticking to it

Hightower · 28 January 2008, 23:35

Oh, I might have come up with a problem....Oh yes the dreaded "space" word! As you can see in the photo's I would want my fibreglass masts mounted in the same position as the plastic poles and as they will protude into the RIB much more they will fowl the control cables and wires as well as the access hatches. Hummm!

Pete7 · 29 January 2008, 09:05

Quote:

Originally Posted by Hightower

Oh, I might have come up with a problem....Oh yes the dreaded "space" word! As you can see in the photo's I would want my fibreglass masts mounted in the same position as the plastic poles and as they will protude into the RIB much more they will fowl the control cables and wires as well as the access hatches. Hummm!

Not to mention any chance of fitting an auxillary. How about a single pole to one side, there is a red rib near to you with a single pole fitted

Pete

9D280 · 29 January 2008, 09:15

Two thoughts:

With regard to the outside layup, I noticed in Halfords a few weeks ago they have some very fine weave glass mat. I'm about to build a protective shell for my VHF which due to space is now hanging off the side of the Console, and like you want to make it as neat as possible. My plan was to build the shell, outside mould it over an ice cream tub, then a layer of gelcoat and then the tedious bit - gentle sanding in ever decreasing grain.....

What do you plan to mount up there? On my old SR I used abit of 40mm exterior rated plastic waste pipe, screw'n'glued a stopper access lid on the end, which I drilled and bolted the raider antenna to. Stayed up OK, but needed stainless brackets on the transom (Made from those cheeeep & nasty chain plates for dinghy shrouds made from a bent bit of stainless strip straightened out & bent to a suitbale radius. I guess if you're adding nav lights & GPS antenna that theory might not be sturdy enough!

9D280 · 29 January 2008, 09:24

Why didn't I think of this 2 mins ago......

Why not find a couple of broken windsurfer masts - they are super strength fibreglass poles

Hightower · 29 January 2008, 10:14

The mast is really only for mounting the normal stuff, lights, Flags, VHF Aerial and GPS Aerial. I did like the Idea of mounting a Rod holder on there as well so strength isn't really a problem in the choice of mast I use. I just liked the Idea of making a one off design in part as a little project, just to see if I could do it and in part to compliment the look of the RIB.

Matt · 29 January 2008, 16:12

For a 1 off, I would make it out of foam, then glass over the top of the foam, then fill and fair (which if you use the right glass and are tidy, won't need too much). If you like it and want to make a lot more, it becomes the plug. The foam will actually add a lot of rigidity to it too.

Simon B · 29 January 2008, 17:59

Quote:

Originally Posted by jwalker

OK. Firstly I'm presuming you're fully familiar with the wee red book so I'm ignoring the polishing and all the other necessaries.

What wee red book? I'm on team with a moulding in grp project at present. I've not done any for years and I've had a lot of rum since I last did so have forgotten almost all of it.

Hightower · 29 January 2008, 20:35

Quote:

Originally Posted by Simon B

What wee red book? I'm on team with a moulding in grp project at present. I've not done any for years and I've had a lot of rum since I last did so have forgotten almost all of it.

I know what he's talking about

Ian M · 29 January 2008, 22:45

Quote:

Originally Posted by Hightower

B'sides don't fibreglassing like warmer temps....

Certainly hope not, otherwise might be picking up bits of console for quite some time

The Garfish · 30 January 2008, 13:50

Quote:

Originally Posted by Simon B

What wee red book?

dem jokstrapps arr orl fkin comyewnists sow itts probubly de thorts ov chareman maow

gArf