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Old 28 January 2008, 16:48   #1
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Fibreglassing a Mast?

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?
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Old 28 January 2008, 16:55   #2
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Andy, is it open at the top? Are you making more than one?
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Old 28 January 2008, 17:02   #3
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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.
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Old 28 January 2008, 17:36   #4
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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.

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Old 28 January 2008, 17:37   #5
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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.
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Old 28 January 2008, 17:41   #6
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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.
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Old 28 January 2008, 17:53   #7
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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
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Old 28 January 2008, 18:02   #8
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Quote:
Originally Posted by Hightower View Post
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.
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Old 28 January 2008, 18:08   #9
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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
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Old 28 January 2008, 18:35   #10
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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!
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