Bending plastic sheet.

[jonjo]

I am planning an unusual boat project that would involve bending a 6' x 2' sheet of thick (10mm?) plastic into a 3 sided shape finished as three 2' x 2' sides. The two outer sides would need to be permanently bent back about 60 degrees relative to the central portion, along a straight fold line.

Soft shatter proof polythene would be idea but if this does not like being subject to heat and shaping, then a harder washboard type plastic would do.

Is there a Hampshire based workshop that could undertake this moulding work? I see fairly complex plastic mouldings at supermarket checkouts these days that appear to have been shaped from flat sheet using heat, so hope this work is feasible.

 

[oldsaltoz]

Not too sure what you are planning but I doubt any of the plastic laminated sheets (Shatter proof) will bend much at all. This may mean using a single layer laminate, and if you need strength perhaps Lexan, it can be shaped. However if it should break it will not be nice little bits with rounded corners, but rather slithers of sharp edges.

A Little more information might help.

Avagoodweekend......

 

[boatbuilder]

Do a search for perspex shop fittings. they use strip heaters to only heat a small strip where the bend is. Specialist job on big jobs. Ive bent small jobs using hot air guns but still a bit hit and miss.

 

[jonjo]

[ QUOTE ]
A Little more information might help.

[/ QUOTE ]
Some background. For the past year I have successfully used plastimo 3/4 round dock fenders to assist in solo or shorthanded berthing in my permanent marina slot. To leave singled handed, I put the engine slow ahead (19hp 1100rpm), release the aft spring and let the bow push into the forward dock fender. My 90 degree plumb bow means the dock fender firmly grips the bow. I then apply some helm to push the aft quarter into another dockfender fixed to the end of the finger pontoon. With the helm locked I can then remove all lines at a leisurely pace. Finally I apply some opposite helm, the stern pivots away from the finger pontoon, then I can leave astern with a useful clearance from the finger pontoon the moment the bow disengages from the forward fender. If my marina neighbour is out I can pivot the hull 20 degrees away from the finger pontoon before engaging reverse engine.

You can probably guess the return mooring process. I try to halt the boat about a meter short of the forward dock fender, then motor into it with less than 1kt of boat speed.

I am planning a 2 month solo cruise and want to replicate this berthing technique at other marinas using a detachable bow bumper. I imagine the readymade bow fenders are virtually useless for my intended purpose because they would pop out of position easily if there is any sideward motion.

Plastimo make a foam filled 1/2 round fender that is 2-3 feet long. I need to attach this fender to a large piece of plastic bent to the shape of my bow. The key thing is the plastic sheet needs to wrap the bow by about 2 feet each side to provide some lateral support to the fender forward of the bow. I plan to line the inside surface of the plastic moulding with wetsuit neoprene or similar. Allowing for the bulk of the wetsuit lining and the width of my hull stem, I think this means the forward flat surface of the plastic would be around the width of the plastimo fender.

If there was doubt about the flexibility of the plastic I could add a 3/4" softwood plinth to the forward face and attach the fender to this.

Essentially I want to be able to hit the pontoon at up to 1.5kts without turning my anchor locker into a crumple zone.

 

[bilbobaggins]

What will you do with this large lump of rigid plastic while on passage....?

Why don't you speak to Henshaw Inflatables Ltd ?

I believe you'll find they can offer you a good solution.

/forums/images/graemlins/wink.gif

 

[DJE]

One of these?

 

[jonjo]

[ QUOTE ]
What will you do with this large lump of rigid plastic while on passage....?

[/ QUOTE ]
Fair ploint. I view it as a one-off for a special journey, anyhow when single handing there will be a spare sleeping cabin footwell or it would slide nicely down the side of the saloon table assuming I have not stuffed a couple of fenders in that space.

 

[Searush]

Most people would set up fenders & bow & stern warps before entering marina. Coil both warps & lead outside everything to a suitable point amidships (I use cabin top). Motor slowly into berth aiming to stop just in or beyond it. Pick up both coiled warps in one hand & step onto pontoon. Snub bow warp around nearest cleat to stop boat & then tie off stern & bow warps under total control. Add springs as required.

A lot less prone to error in my view. If you have a problem reversing out, warp her to the end of the pontoon & set her up for an easy departure (you can turn her completely if required). Set up warps doubled around the pontoon cleats & release from on board as you leave. Warping boats around docks for safer departure was a common technique used by engineless windjammers (tugs were expensive).

 

[ean_p]

Polyprop sheet of 10mm is easily bent as you require, almost any plastics supplier will do it for you for very little cost . If you want to do it your self you'll need a good high temp heat gun with nozzel attachment ...try google 'Leister' and /or e-bay it. hardest part would be achiving the line and I would think in terms of clamping between two bits of 2" angle iron then heat and bend over as required.

 

[jonjo]

[ QUOTE ]
Most people would set up fenders & bow & stern warps before entering marina. Coil both warps & lead outside everything to a suitable point amidships (I use cabin top). Motor slowly into berth aiming to stop just in or beyond it. Pick up both coiled warps in one hand & step onto pontoon.

[/ QUOTE ]
Well obviously this often goes wrong otherwise yachting magazines would not provide advice on the subject year after year. Motoring into a berth slowly is not always an option due to tidal current and cross winds.

Maybe your experience of mooring is different because your boat makes a bigger hole in the water than mine and so is less skittish. Another factor is that I drive my 35 foot boat about 18" from the stern and there is a large racing wheel to get around, so those coiled ropes on the coachroof seem further way when singlehanding.

Leaving the berth is not usually a problem. I often manhandle the hull and create a 1/2 kt of boat speed before hoping aboard and engaging the engine.

Since discovering the technique of driving the bow into a dockfender, other methods now seem unnecessarily problematic.

 

[jonjo]

Some other points:

Average boat lengths have risen steadily over the past decade but marinas have not been rebuilt to allow for this hence these days we often have to berth alongside relatively short finger pontoons. Inevitably larger boats protrude further out so there is less turning room between marina jetties than 10 years ago.

Modern bows, even for cruising yachts, have much less rake. A classic 25 year old design has say a 40 degree rake, so during that once a year overshoot energy will be taken out of the collision as the bow rides up over the pontoon by a few inches. With a modern design 5 tons of energy has nowhere to go unless the whole jetty gives and moves back a few inches.

 

[ShipsWoofy]

I had my heads floor step bent in by Ensinger Ltd, Waterlooville. Even though I bought from Warrington the work was carried out dan your way.

Excellent source or uPVC board and poly sheets. Also perspex. I have had a few bit and pieces from them and have been very happy with the service I have received.

J