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Old 28-05-2024, 12:28   #1
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Patterning the cabin trunk.

Hi all,

We will soon be building our deckhouse and we want to make it look as much as possible like it was part of the original boat. To that end we’d like to duplicate the shape of the cabin trunk, the same curve radius and side angles.

We will be building with polyester on pvc honeycomb board, which we’ve found to be a great way of building the interior. We played around and discovered the board produces lovely even curves (in one dimension at least) if we run parallel shallow cuts on the inside face.

But I’m not yet sure of the best procedure for duplicating an existing curve. So far we’ve just made a curve that felt right for the particular interior component we were building, taped it in place then hit it with the glass and resin. But those have all been small parts, I don’t think that technique will work for the deckhouse. (Which will be approximately 2 meters long per side and a bit under 1 meter high.)

This is a call out for any links or descriptions of patterning techniques you’ve found work for you. We are pretty comfortable working with this stuff but we are a very long way from professional and don’t want to have to tool up hugely for this one job.

Ideas?

Matt
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Old 28-05-2024, 16:56   #2
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Re: Patterning the cabin trunk.

Matt

When I did it I used "bendy ply" over a former. You might get some ideas here.

https://www.google.com.au/search?sca...&bih=615&dpr=1




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Old 28-05-2024, 17:39   #3
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Re: Patterning the cabin trunk.

Tick or joggle sticks.
You have to make your own

I save large pieces of cardboard for the pattern transfer

One example:
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Old 28-05-2024, 22:22   #4
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Re: Patterning the cabin trunk.

Various techniques including templates of core-flute or craft board strips glued together.
Precise fitting jobs often require 2 generations of template.

Sometimes I'll make do with a first gen template and cut the PVC core oversize.
Easy enough to trim with a knife, sure form or multi tool.

Sometimes I skin the downside / inside with a finished layer of 450 gsm bi axial.
Present the rough shape to the job and trim to fit with multi tool.

Securing the skinned side zip ties, clamps, glue allows for construction of complex curves.
Heat gun is useful for inducing some memory into the panel before finalising the lay up.

For radiused corners , edges avoid butt joins.
Pick a std radius and find some PVC pipe to match.

Leave a gap beteen the panels, present the pipe to the section do a couple or few layers of glass around the curve.
Remove pipe and repeat lay up from the other side.

This brings the skins together for a stronger join and panel with a consistent radius that will require less effort to finish and pain prep.

For tight curves, lay in a one sided panel in 6mm core then laminate another one sided panel glass side out.

A layer of chop strand wetted out with thickened resin give a strong bond free of voids.

If you're building a surface that needs to take compression e.g. foot traffic try infusion core.

It has a pattern of holes that fill with resin resisting compression by a much as an extra skin on each side.
Reduced materials, weight and labour.

Technique is king.
Develop what works for you cleanly and reliably.

Clean up and finishing are major cost components.
Reduce or eliminate.


Hope this helps.
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Old 29-05-2024, 00:44   #5
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Re: Patterning the cabin trunk.

Quote:
Originally Posted by GILow View Post
Hi all,

We will soon be building our deckhouse and we want to make it look as much as possible like it was part of the original boat. To that end we’d like to duplicate the shape of the cabin trunk, the same curve radius and side angles.

We will be building with polyester on pvc honeycomb board, which we’ve found to be a great way of building the interior. We played around and discovered the board produces lovely even curves (in one dimension at least) if we run parallel shallow cuts on the inside face.

But I’m not yet sure of the best procedure for duplicating an existing curve. So far we’ve just made a curve that felt right for the particular interior component we were building, taped it in place then hit it with the glass and resin. But those have all been small parts, I don’t think that technique will work for the deckhouse. (Which will be approximately 2 meters long per side and a bit under 1 meter high.)

This is a call out for any links or descriptions of patterning techniques you’ve found work for you. We are pretty comfortable working with this stuff but we are a very long way from professional and don’t want to have to tool up hugely for this one job.

Ideas?

Matt
It would help if you cn make clear exactly which surface you want to template. A picture?
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Old 29-05-2024, 02:10   #6
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Re: Patterning the cabin trunk.

Quote:
Originally Posted by 5BTM View Post
Tick or joggle sticks.
You have to make your own

I save large pieces of cardboard for the pattern transfer

One example:
Thank you, the name rings a bell, I’ll look into their application for this job.
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Old 29-05-2024, 02:12   #7
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Re: Patterning the cabin trunk.

Quote:
Originally Posted by Rucksta View Post
Various techniques including templates of core-flute or craft board strips glued together.
Precise fitting jobs often require 2 generations of template.

Sometimes I'll make do with a first gen template and cut the PVC core oversize.
Easy enough to trim with a knife, sure form or multi tool.

Sometimes I skin the downside / inside with a finished layer of 450 gsm bi axial.
Present the rough shape to the job and trim to fit with multi tool.

Securing the skinned side zip ties, clamps, glue allows for construction of complex curves.
Heat gun is useful for inducing some memory into the panel before finalising the lay up.

For radiused corners , edges avoid butt joins.
Pick a std radius and find some PVC pipe to match.

Leave a gap beteen the panels, present the pipe to the section do a couple or few layers of glass around the curve.
Remove pipe and repeat lay up from the other side.

This brings the skins together for a stronger join and panel with a consistent radius that will require less effort to finish and pain prep.

For tight curves, lay in a one sided panel in 6mm core then laminate another one sided panel glass side out.

A layer of chop strand wetted out with thickened resin give a strong bond free of voids.

If you're building a surface that needs to take compression e.g. foot traffic try infusion core.

It has a pattern of holes that fill with resin resisting compression by a much as an extra skin on each side.
Reduced materials, weight and labour.

Technique is king.
Develop what works for you cleanly and reliably.

Clean up and finishing are major cost components.
Reduce or eliminate.


Hope this helps.
This is amazing stuff. I’m rather wishing I’d asked this question about two years ago when we started this project.

Thank you, lots to digest, but very clearly described.
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Old 29-05-2024, 04:08   #8
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Re: Patterning the cabin trunk.

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Originally Posted by s/v Jedi View Post
It would help if you cn make clear exactly which surface you want to template. A picture?
This curve.
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Old 29-05-2024, 05:34   #9
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Re: Patterning the cabin trunk.

Quote:
Originally Posted by GILow View Post
This is amazing stuff. I’m rather wishing I’d asked this question about two years ago when we started this project.

Thank you, lots to digest, but very clearly described.
Glad it made sense to you.

What it the existing cabin trunk made from?

If composite it can be remodeled by sectioning, adding or subtracting material
Much like doing chop on a car but easier.

If the cabin is solid construction it could be the basis for a template / mould.
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Old 29-05-2024, 15:08   #10
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Re: Patterning the cabin trunk.

Quote:
Originally Posted by Rucksta View Post
Glad it made sense to you.

What it the existing cabin trunk made from?

If composite it can be remodeled by sectioning, adding or subtracting material
Much like doing chop on a car but easier.

If the cabin is solid construction it could be the basis for a template / mould.
The trunk is timber cored fibreglass, and a pretty hefty layup at that. 1978 Taiwanese yard, they didn’t skimp.

I am going to attempt to use the trunk as the mould, but I think it will get too awkward with the big sheets of honeycomb pvc, hence my question about patterning.
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Old 29-05-2024, 17:01   #11
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Re: Patterning the cabin trunk.

Handling large sheets can be problematic.

Revisit publications from West Systems re strip planking and diagonal timber layups.

The techniques are easily adapted to male mould composite foam construction.

You could work on a half or quarter mould and stick the pieces together to reduce space requirements.

You mentioned Honeycomb.

If its a true honeycomb - more holes than structure - wet hand layup is not optimal.
This is pre-preg, vacuum bag, autoclave territory to avoid heavy, expensive resin rich panel.

80-120 gram PVC foam e.g. core-lite would be my choice
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Old 29-05-2024, 17:15   #12
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Re: Patterning the cabin trunk.

May help: https://www.cruisersforum.com/forums...ps-175159.html
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Old 29-05-2024, 18:24   #13
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Re: Patterning the cabin trunk.

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Originally Posted by deblen View Post
Oh dear, that old chestnut. Went through it a few months ago, but I admit I was looking for design ideas, not techniques.

Some of those add ons are really hard on the eye. But I’ll go through it again and see if I can glean anything useful.
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Old 29-05-2024, 18:27   #14
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Re: Patterning the cabin trunk.

Quote:
Originally Posted by Rucksta View Post
Handling large sheets can be problematic.

Revisit publications from West Systems re strip planking and diagonal timber layups.

The techniques are easily adapted to male mould composite foam construction.

You could work on a half or quarter mould and stick the pieces together to reduce space requirements.

You mentioned Honeycomb.

If its a true honeycomb - more holes than structure - wet hand layup is not optimal.
This is pre-preg, vacuum bag, autoclave territory to avoid heavy, expensive resin rich panel.

80-120 gram PVC foam e.g. core-lite would be my choice

Yeah, it’s the true honeycomb stuff. We’ve been working with it for two years now and we are getting ok results. Wouldn’t want to be building a foiling race boat, that’s for sure, but it serves our purpose.

Good point about the strip technique, I’ll keep that in mind.
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Old 30-05-2024, 06:24   #15
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Re: Patterning the cabin trunk.

I recommend you watch the episodes of the Duracell Project on Youtube. He has been doing exactly the same stuff except using foam core.

Go back a little in his episodes because the later ones he is so proficient that he doesn’t show the process in as much detail as earlier on.

He does the joggle sticks too.
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