Making a plug from a spray hood

[Vara]

Probly a silly idea, I have a canvas spray hood with window, fills in gap between roll bar/Targa and fixed screen (Malo).

In five years have never folded the thing and it is due for replacement.

What I would like to do is make/have made a fibre glass replacement with window.

How could I take an impression of the hood in situ to enable a replacement to be made.

Or any other ideas for a way forward.

 

[pmagowan]

I think it is unlikely that a canvas sprayhood would be accurate enough to form some kind of mould over. You would end up with some odd creases and sags. I would simply take measurements and impressions of the coachroof where it is attached so that you can recreate that part back at home where it wil be easier to design a mould around it. Then all you really need to do is sketch what you want, make plyboard 'frames' and then put thin strips of wood over it to make your male mould. If you want a female version then you could either take it from a glassed up mould from the male plug or you could build up the mould on the inside of the plywood frames, if you know what i mean.

In either event I dont think it would be difficult although a little pernickety and time consuming depending how perfect you want it. It would certainly give you a better product than if you try to create an 'in situ' mould over the fitted sprayhood. It should only be used for rough measurements. The only way I can think you could do it the way you are talking about is to either use papier mache or to put a large sheet of acrylic over it and hit it with a blow torch or hot air gun. Both seem doomed to failure in my opinion.

 

[Hypocacculus]

I've never done this, but I've done enough sewing to know that any shape made by sewing is basically an exercise in making a 3D shape out of flat bits of fabric.

the spray hood will be made of a number of canvas sections. If you take the hood apart and lay the sections out, you could possibly use them to mark thin pieces of plywood. These pieces could then be bent and fixed together along the "seams" to form the same shape. The limitation will be the bendability of the ply.

 

[pmagowan]

I've never done this, but I've done enough sewing to know that any shape made by sewing is basically an exercise in making a 3D shape out of flat bits of fabric.

the spray hood will be made of a number of canvas sections. If you take the hood apart and lay the sections out, you could possibly use them to mark thin pieces of plywood. These pieces could then be bent and fixed together along the "seams" to form the same shape. The limitation will be the bendability of the ply.

I don't think the ply will take the compound curves that the fabric will and it certainly won't stretch where needed. You can make a crude sprayhood design using flat pieces of ply and you see these regularly enough. They look a bit odd to my eye especially when on a nicely shaped boat rather than a hard chined one. I don't think building a proper strip planked mould is too arduous. In fact you could make up cardboard 'frames' running longtitudinally with the boat on the inside of the current sprayhood at set distances and use these to transfer the patern to ply frames on which to build the mould. I recon it would take 1 weekend to get the rough mould finished and then it would need some fairing prior to being used to build up the glass fibre.

 

[bigwow]

If your hood is scrap anyway, you could try laying foam over it, using a hot air gun to shape and fibreglassing over then remove and fibreglass the inside, ending up with a foam sandwich hood.

 

[Elessar]

View attachment 43655Probly a silly idea, I have a canvas spray hood with window, fills in gap between roll bar/Targa and fixed screen (Malo).

In five years have never folded the thing and it is due for replacement.

What I would like to do is make/have made a fibre glass replacement with window.

How could I take an impression of the hood in situ to enable a replacement to be made.

Or any other ideas for a way forward.

It would look very low rent in your fine vessel. You need compound curves not saggy simple curves.

Make a plug out of thin ply attached to the frame, ribbed inside with 2x1 for rigidity.
Add layers of structural foam. probably 2. Maybe even 3 in the middle.
Make a shape with a long board. Nice compound curves. May be quite flat in the middle to match your boat but it will be curved edges to look right.
Paint it white and paint black where the "glass" will be remember simple curves for the glass so mark cut a 3 mm piece of ply for each glass bit.
Keep sanding till you're happy with the shape from all angles. Will have to paint it again as you can only scrutinise the shape if it is an even colour.
Glass over it, then fill and fair. Hack away the foam.
Flow coat the lot. Sand and polish. Flow coats the bits you sanded through. Sand and polish.
Cut out window holes. Ta nah.

 

[Lakesailor]

If I may be so bold.
The spray hood is a bit of a carbunkle on the handsome screen.
Instead of spending time and money trying to reproduce it, why not get a new top designed to match the screen surround, (in alloy and plexiglass) so that it looks very much of a piece?
Or even a a new deckhouse

 

[FullCircle]

Project Plastics in Colchester were the best price I got for a screen and additional hard top made together. £5.2k inc tooling (very rudimentary.
IIRC, the hard top bit was about £1.5k, with a stainless grab rail on the rear edge.

 

[nimbusgb]

Get a few sheets of airex pvc coring foam, 6mm thick and lay it up over the frame. It can be heat formed into compound curves. Lay up glass over it. Lift off and remove foam in 50 mm wide stringer positions and edges and lay an inner skin leaving most of the sandwich in place.

Getting it to look better than a glassed over sprayhood is going to be tough. As has been said, very low rent.

 

[bigwow]

Get a few sheets of airex pvc coring foam, 6mm thick and lay it up over the frame. It can be heat formed into compound curves. Lay up glass over it. Lift off and remove foam in 50 mm wide stringer positions and edges and lay an inner skin leaving most of the sandwich in place.

Getting it to look better than a glassed over sprayhood is going to be tough. As has been said, very low rent.

Isn't that what I said in #5?

 

[conor54]

This might give you some ideas...

Steve Marshall Hard Dodgers for Sailboats : https://plus.google.com/photos/104699851678301047425/albums/5050832519201406417?banner=pwa

 

[oldsaltoz]

Forget about trying to reproduce what you have and take lots of pictures of the are fron from all 4 sides.

Use these to redesign your new cockpit cover by drawing on the picture and use curves about the same size as others in the area so it looks like it was designed with the boat when new.

The use a closed cell foam as the basic structure and add any supports, avoiding any ply panels by the way.

I would be tempted to continue the line of the screen from top to bottom with well rounded sides, this will look better and be stronger. Adding a couple of clear forward opening hatches on the front section will not only replace that horin little angled window but also provide better ventilation.

Also note, the foam can be gouged out on the underside to provide space for concealed wiring, speakers, navigation lights, domestic radio and even solar panels. Also consider some extra clear panels for checking on sail trim and so on.

Just don't rush it, take your time, make up a cardboard mock up to check it's appearance before you build the real thing.

Good luck and fair winds.

PS you are lucky, yours is pretty small, ours was almost 20 feet feet wide and 12 feet long (42 foot Cat).

 

[Vara]

Many thanks for everybody's input.

plenty of food for thought.
a complication is that any new spray hood arrangement should be completely reversible for resale purposes.

Exploring the tecniques and skills required would indicate that I would have to get professionals to do all/a lot of the work which would probably rule it out costwise. However I shall keep the idea on ice.

Thanks again.

 

[pmagowan]

You should be able to mould fibreglass in your garage with virtually no tools. A tape measure, saw, sandpaper +/-plane, a stapler or hammer and nails, a few sheets of ply and a WEST system kit.

 

[Lakesailor]

I wouldn't bother using epoxy for a cover like that. Polyester grp is much cheaper. These people are dependable http://www.ecfibreglasssupplies.co.uk/