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[Mohawk Nick]

Hello all! I've spent the last couple of weeks building a diy vacuum former in order to scrtch build some vents so here is a short description of how i did it and some results.

The vacuum former was made from melamine which is plastic coated chipboard that fitted kitchens or wardrobes are built from. To create a good seal i assembled the box with household silicone bath sealant which i applied along the joints in a continuous bead like you would PVA wood glue. The frame for the plastic sheet is an old A5 picture frame that i strengthened with two strips of hardwood. I used double sided foam tape to fix the plastic sheet to the frame then placed a second frame over the sheet when under the grill. I found this didn't need clamping down to stop the edges of the plastic sheet from curling up+allowed for quick removal prior to vacuum forming. The white strip around the bed of the box is household sticky backed rubber draft excluder strip, this creates a great airtight seal when the frame and plastic sheet is placed over it. The holes in the bed are approximately 20mm apart.

The patterns for the vents were made from model board. On the first run the plastic kept forming into ridges around the base of the vents due to their shape. To overcome this i lengthened the patterns so that i could simply cut the base away to leave the top of the mold which wasn't effected.

The ridges can be seen in this photo.

Excess plastic removed leaving the base and vent.

The assembled vent with additional detail which includes a grab rail which runs around the back of the vent and i assume was used for rotating it.

This vent was made using the same pattern as the first but has a lengthened flue and sits directly behind the forecastle.

This vent required a different pattern for its base and top. It sits just behind the forward torpedo tube and has a squashed opening to allow the torpedo tube to pass under it without fouling.



I've included this photo to show the difference between the size and shape of the vents when made to scale next to one included with the kit.

[boatmadman]

Nice job.

A couple of questions:

What is model board? Is it a hard foam type product?

What did you use for heat to help the forming?

Did you use a domestic hoover for the suckage?

Ok, I lost count, 3 q's.

Ian

[Mohawk Nick]

Hello Ian! Model board is a medium density modelling material used in architectural model making or for pattern making. It also comes in a high density form and can be machined, sculpted, drilled etc etc. Its available from easycomposites.co.uk.
I used the cooker grill at home to heat the plastic. Pop your frame and plastic under the grill at least 3inches away from the filament. The plastic will ripple and then go taut at which point its ready to go.
Finally, yes a domestic hoover was used. I would recommend a Dyson if you can get hold of one. If not make sure your hoover has an empty bag and clean filters as this will help.
I hope this helps! Nick.

[TailUK]

The rippling is caused by the excess plastic not being able to shrink enough as it forms.  You see it worst on tall patterns especially those with square corners. the ripples on yours arn't as bad as they could be as you have a rounded base section.  One way around it is to out a ring around your pattern or small blocks near the pattern which take up the slack as it were

[HS93 (RIP)]

some one I know does it he uses MDF and softwood any wood will do the pattern I made was PLY , the base had a lot more holes , they can be taped over if not  needed, you need to make several holders for your sheet material that way you don't waist much material , but as has been said custom bases with the holes in are needed , normal vac is fine go on u-tube there are lots of demoes, but make it so it can be adapted for different sizes then you get no waist and you can play about

Peter