Repair & maintenance: Cutting Acrylic Transom Flaps

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Cutting Acrylic Transom Flaps

Printed From: Yachts and Yachting Online
Category: General
Forum Name: Repair & maintenance
Forum Discription: Questions & tips on the subject
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=10669
Printed Date: 14 May 25 at 12:45pm
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Topic: Cutting Acrylic Transom Flaps

Posted By: rb_stretch
Subject: Cutting Acrylic Transom Flaps
Date Posted: 29 Jan 13 at 10:15pm

Did some gelcoating today as discussed in other thread. Whilst doing it I snapped my transom flaps which were made out of clear acrylic, about 2 mm thick.

Went to Wickes today to buy a sheet and have just spent the last 2 hours trying to cut the flaps out but failing. Using just a stanley knife was impossible (it's got curves), jigsaw split it, saw was the same. I had most luck heating a knife up repeatedly with a blow torch, but split them when trying to take out of the sheet.

So how do people cut their transom flaps?

Replies:

Posted By: sargesail
Date Posted: 29 Jan 13 at 10:26pm

Buy the material from P&B or similar and it's cutable. I used both scissors and a scalpel.

Posted By: iGRF
Date Posted: 29 Jan 13 at 11:17pm

Hot Wire?

Posted By: transient
Date Posted: 30 Jan 13 at 1:10am

Never had a boat with flaps but.....I,d use polycarbonate and cut with a fret saw. Polycarb will last much longer. The local sign writers/engravers should have some.

Posted By: MattTrinder
Date Posted: 30 Jan 13 at 7:29am

I bought polycarbonate sheet off eBay.

Posted By: Oatsandbeans
Date Posted: 30 Jan 13 at 7:34am

The best would be a band saw with a narrow blade so that it can do the curves. If none of your mates has one I think that it would be possible with a good jigsaw. With the right blade, not too agressive -many small teeth, and get the speed right up before you start the cut then it wont have a chance to shake the sheet about and ruin it, once it is cutting properly it should then be OK.

Posted By: MerlinMags
Date Posted: 30 Jan 13 at 9:05am

If you have to use a saw, perhaps sandwich the plastic between two layers of scrap wood, to keep it from flapping.

Or get those scissors which can cut through 2p coins (if I remember the advert rightly?).

Posted By: RichTea
Date Posted: 30 Jan 13 at 10:17am

Tape it with masking tape first between the two cuts, ie down the join.

Posted By: laser193713
Date Posted: 30 Jan 13 at 10:30am

Ah the joys of having access to a CNC machine!

Posted By: Jack Sparrow
Date Posted: 30 Jan 13 at 11:46am

fret saw or tile saw and then sand down edges

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Posted By: rb_stretch
Date Posted: 30 Jan 13 at 1:35pm

It seems the Wickes acrylic sheet is particularly fragile as I just tried scissors which caused it to fracture all over the place. Oh well £18 down the drain.

Need a plan B now.

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Posted By: JohnW
Date Posted: 30 Jan 13 at 1:44pm

Is this for your Alb? If so, most boats use a flexible sheet that can be cut with scissors.

This kind of thing:

http://www.sailboats.co.uk/Catalogue~Mylar_Transom_Flap_W50cm_L30cm~p_K903~c4657.html - http://www.sailboats.co.uk/Catalogue~Mylar_Transom_Flap_W50cm_L30cm~p_K903~c4657.html

http://www.kitronik.co.uk/products/perspex/pvc-and-flexible-plastics/pvc-flexible-sheet-single/ - http://www.kitronik.co.uk/products/perspex/pvc-and-flexible-plastics/pvc-flexible-sheet-single/

But if you can get some clear stuff that is better, so that you can check fore and aft trim through the flaps where the water leaves the transom.

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Posted By: Jack Sparrow
Date Posted: 30 Jan 13 at 2:42pm

Originally posted by rb_stretch

It seems the Wickes acrylic sheet is particularly fragile as I just tried scissors which caused it to fracture all over the place. Oh well £18 down the drain.

Need a plan B now.

use a very fine tooth fret saw or an abrasive tile saw and then sand the edges down! Or trim with a wide amount of spare and sand in down with a rotary power sander, either bench or drill or grinder.

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Posted By: rb_stretch
Date Posted: 30 Jan 13 at 2:54pm

Originally posted by JohnW

Is this for your Alb? If so, most boats use a flexible sheet that can be cut with scissors.

This kind of thing:

http://www.sailboats.co.uk/Catalogue~Mylar_Transom_Flap_W50cm_L30cm~p_K903~c4657.html - http://www.sailboats.co.uk/Catalogue~Mylar_Transom_Flap_W50cm_L30cm~p_K903~c4657.html

http://www.kitronik.co.uk/products/perspex/pvc-and-flexible-plastics/pvc-flexible-sheet-single/ - http://www.kitronik.co.uk/products/perspex/pvc-and-flexible-plastics/pvc-flexible-sheet-single/

But if you can get some clear stuff that is better, so that you can check fore and aft trim through the flaps where the water leaves the transom.

Yes for the Albacore. The Mylar looks like it will be much more robust than Acrylic, so definitely worth considering.

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Posted By: rb_stretch
Date Posted: 30 Jan 13 at 2:56pm

Originally posted by Jack Sparrow

Originally posted by rb_stretch

It seems the Wickes acrylic sheet is particularly fragile as I just tried scissors which caused it to fracture all over the place. Oh well £18 down the drain.

Need a plan B now.

use a very fine tooth fret saw or an abrasive tile saw and then sand the edges down! Or trim with a wide amount of spare and sand in down with a rotary power sander, either bench or drill or grinder.

The only challenge I have with using saws which are not just a blade is that I can't cut the flaps big enough. I think in my next go I'm going to use the scoring and snapping technique gradually working down to the approximate shape and then belt sander to smooth it out.

Will report back.

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Posted By: rb_stretch
Date Posted: 30 Jan 13 at 5:21pm

Problem solved.

I needed to drop some fids I had borrowed from Guildford Marine and they basically said that Acrylic was a lost cause in the way I intended to use it ie. it would always be susceptible to shattering (as with the original flaps). They basically sold me an offcut of 1.5mm Lexan, which seems far more robust. Going to try and cut that with a stanley knife. The also sold me an offcut of aluminium keel band to hold the flaps against the hull on the inside edge.

Makes you realise you can't do everything through internet chandleries.

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Posted By: sawman
Date Posted: 30 Jan 13 at 7:05pm

I need to replace transom flaps at the moment - the current ones are very heavy and hinged. Is 1.5mm lexan flexible enough to be fixed without a hinge?

I wondered if 1mm might be more flexible

Posted By: rb_stretch
Date Posted: 30 Jan 13 at 10:17pm

I have 1.5mm and it is easily flexible enough to use without a hinge.

Having said that this is on an Albacore with some pretty big flaps. If they are small then I think 1mm might be better (in actual fact Guildford Marine do use 1mm for smaller flaps and 1.5mm for bigger ones)

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Posted By: sawman
Date Posted: 31 Jan 13 at 7:02am

cheers, the old flaps on my miracle are about 4 inches across. I am tempted to make a hinge with shockcord passing though, having seem a couple of pics on the net.

There seems to be a huge supply of lexan in different thicknesses on ebay, at a reasonable cost compared to the pinbax item linked to earlier

Posted By: Jack Sparrow
Date Posted: 31 Jan 13 at 4:00pm

Plastic Direct LINK http://www.directplastics.co.uk/polycarbonate-sheet - http://www.directplastics.co.uk/polycarbonate-sheet

with does it stick this in the code! (=%20)!!!!!

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Posted By: sawman
Date Posted: 31 Jan 13 at 5:22pm

I have just been down to bayplastics in newcastle http://www.bayplastics.co.uk/, and they are going to cut me a couple of flaps for a couple of quid - this should avoid any of the OP's troubles for me

Posted By: winging it
Date Posted: 31 Jan 13 at 5:55pm

I found a cut up ice cream tub was excellent - lightweight, easily fitted and you get to eat the ice cream first!

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the same, but different...

Posted By: sawman
Date Posted: 31 Jan 13 at 6:29pm

Originally posted by winging it

I found a cut up ice cream tub was excellent - lightweight, easily fitted and you get to eat the ice cream first!

I thought about that, but it would cost more in Ice cream than Lexan. Also, ice cream tubs are not usually clear, and the miracle is quite sensitive to fore/aft trim, so its useful to peer through the transom flaps from time to time

Posted By: rb_stretch
Date Posted: 01 Feb 13 at 6:47am

Originally posted by winging it

I found a cut up ice cream tub was excellent - lightweight, easily fitted and you get to eat the ice cream first!

One of my other thoughts was to use polyethylene from for example a washing up bowl or one of those storage boxes.

Posted By: rb_stretch
Date Posted: 01 Feb 13 at 5:31pm

Just finished the job today. In the end the best way to make them was to use a Stanley and snap pieces off until you have the rough shape. I then used a belt sander to round off all the corners that were left.