DIY windscreen job.

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    Posted: 04 Mar 2021 at 6:50pm
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So I broke the screen on my Fyran 530 a week ago. Too much green water.
After hunting around I managed to find a supplier who must have an original mould. The boat is about 12 yrs old and the manufacturer no longer exists. The only problem was the screen was going to cost $2k (and add in some freight).
So I decided to take another track as a punt and buy a sheet of 4.5mm perspex and have a crack. The sheet cost $250.
I originally posted my supplier /manufacturer enquiries on another forum and was then asked to post the process here. So here goes.
First I marked the centers on both top and bottom rails and the corresponding points on the broken screen.
The screen was cracked thru in two pieces and a bit more. I taped these together while still in the frames - both sides.
Having marked and taped the screen I removed the top frame then pulled the screen clear of the bottom rail. A few screws to remove here but they came easily.
Now I laid the broken screen on top of my sheet. Transferred the screen center marks to the sheet. leave the protective paper on the sheet. I scribed around the front/flat part of the midsection. Now the tricky bit. You need to get this really accurate to go smoothly. I rolled one corner of the screen partly down on the sheet. I think I actually walked it down. Go part way, scibe, bit more, scribe. I got to a point where standing on the curve I could pull the bottom sheet up fat enough to meet the screen. Scribe. Carefully roll back and check the center marks are still good. Repeat other side.
Cutting. You need to support the sheet close to cutting line. I used two thin planks and a skill saw - fine blade. Cheapo 40T $20 M10.
Set saw just a bit deeper than perspex - ie 5-6mm cut. Easier to follow curves. I could get around them all - the tightest took 2-3 bites. Don't try to follow the curve if saw doesn't want to. Cut thru and come back on another angle. I cut to the inside line of the scribe mark - which was about the blade thickness. So the blade just cut out the scribe line.
Now I had the profile cut I had enough sheet for two screens. So trusting my profile I scribed a 2nd template - for next time.
Now for forming. Remove the paper. Don't forget to transfer center marks to the perspex - don't loose them..
The proper way is to heat the template in an oven and lay on a mould. I don't have an oven or a mould. So I used a heat gun.  
This is a bit tricky because you can only heat a small section - need to get to about 100 deg. Use gloves. Hot.
I clamped the sheet over top of the old screen (use the ref marks) and started with the gun. Slow job.  Took about 2 hrs. Waiting for the sheet to want to drop down on to the screen A little bit of help is OK but if you force it , it will want to yield in the wrong places.
You need to watch the angles and lines that are holding you up getting the shape and work those. Not too much heat in one spot - it will collapse and be hard to salvage. gentle gentle. Repeat. I got an approx contour first time round and went back a 2nd time and then tidied up a 3rd time. Don't drop sweat on the hot screen. Marks it. Sweat off- screen.
I didn't try to get it perfect - just close. Then I fitted it to the top rail - out of the boat. There is some flex in both screen and rail. Use the ref marks. Once in place I ran the heat gun around the corners to relax the screen in place - ie follow the rail rather than rail follow screen.
Then I tried fitting to lower rail - in the boat - without top rail. Same process. Before doing this - de burr the cut edges.  I persuaded it in close but not perfect spots by tapping a wooden block on top of the screen. Once in place - relax with gun again.
Once happy, fitted top rail again - knowing it will fit. Tap down in place. I put some silicon sealer in top and bottom channel prior to final fit. Mine had a rubber sealing strip along top outside edge. I fitted it after fitting the whole setup. Pushed/tapped in place.
Next time.
It is not perfect - it is a compound curve - 2 directions at once . hard to do with a small heat gun. Next time I may try the BBQ for the corner heatings - on a couple of strips of wood - do one and remove and massage in to form over the old corner and repeat other end.
Took me about 4 hrs solo. About 2 hrs marking/removing/refitting. 2 hrs on heat gun.
Good luck.
Alan


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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2021 at 7:02pm
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Excellent.
 Son in law worked with this stuff for yrs. We have used flat sheets for around deck etc.
 1st thing he told be.. don not use sharp tools.
 A drill bit put in the bench wire brush and same goes for cutting blades.

Have a question thu.
If I read correct, you cut the screen to the template, then  put the shape into it.
Why did you not cut the screen out with say a inch or so all round then bend , then trim to size?
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2021 at 7:47pm
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Yep - I guess you could do. The worry my way is you may end up too short somewhere.
I guess you could over size the scribing, form, then cut. One difficulty would be you are forming a bigger area with a limited amount of heat. And the other might be cutting the curved screen. Hard to support it. Easier flat.
I do think cutting the curved product may prove a bit stressful - but if you can happily cover that it may be a better method, avoiding the possibility of being too short somewhere. Tracing my screen out proved a bit easier than I expected tho. So I was reasonably confident in the template. I did end up trimming a few mm out of the base of one corner to get it to sit low enough for the top rail. It was the only adjustment I had to make. It was a bit hairy compared to cutting a flat sheet. Vibrating/flexing. Damaging it after all the time forming it would rip your nighty.
Regards
Alan
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Post Options Post Options   Likes (0) Likes(0)   Quote kimber7wsm Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 6:32am
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Thanks, this will be very useful.
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 7:02am
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Steps - your approach of cutting a wider margin and bending and trimming later may well be a better approach. I only have a depth of experience of one screen to draw on. But if you want enough sheet for a spare - in case you stuff up or need to replace another later - you will need to be careful of the margins . Maybe 10-20mm max. The sheet marked out on the ground is my 2nd template. You can see how much spare margin I had.
What would help tho, especially if a bigger margin than original size, is a 2nd heat gun operated by a helper. You do one side of the bend and they work the other. Getting enough heat across the fold you are working is a challenge. I had a warm sunny day. A cold morning would be even harder.
If two guns, that will be near 3.5Kw, so unless you use the oven circuit to power them, you may pop a few fuses - about 15A
Alan
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 8:41am
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Steps - your approach of cutting a wider margin and bending and trimming later may well be a better approach.

 
No its not actually how I would approach it..
 I am asking questions from an person who has done it.. well.. without a mould and  large oven, any why , if any reason why not.
 Then decide my approach

Its is from experience of others , asking questions why / why not one gets an understanding when comes to doing things ones self.
 My screen was professionally replace by the previous bout owner from a mould of the orginal screen. Once trimed to shape has ended up a inch ir so shorter. This now means the top of the screen and the to bar goes straight thru ones line of sight at the helm.
 Which also maybe something people may consider if replacing their screens in the future..

So that creates another question.
 Do you think, if the plastic was cut maybe 1/2 inch larger all round, then molded to shape... Would those edges enable cutting a little wider than original without any serious , obvious defects around the edge?

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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 10:39am
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"Would those edges enable cutting a little wider than original without any serious , obvious defects around the edge?"

The problem will be a 'loose' edge - unsupported. But don't forget I used a skill saw. It worked perfectly on a flat supported sheet. Didn't force it, but also didn't drag the chain on it (friction heat). But there are other ways that may work better on an unsupported edge. Angle grinder - not sure what sort of blade - have to test first, or jig saw. You would probably want some help to try and move the screen as you cut - so you can get the flex out of it.
I am sure it could be done the way you are suggesting. I would suggest getting a bit of your waste template material, bending it and then see how well you can cut it with what options you have for tools. I did this without taking the boat home to my w/shop. Would have felt better if was in the w/shop - took a pile of tools with me to the job. Never used half them - including jigsaw. Job basically went better than expected.
But an improvement in the bending process would be useful. two heat guns prob worth a shot.  Or the BBQ method.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 12:29pm
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Damn good info Alan.
You think if had a bit of over hang on the outside of the mould, that extra 1/2 to 1 inch may not bend down well  , tidy as what is inside the mould?

When I cut the sheets for the deck doors windows etc.. and a few other things around here and our last home....
I avoided the jig saw...
1/ the new sharp blade tended to very eady put small cracks in the edges (which was where learnt to use blunt tools)
2/ With the blunter blades the blade tended to pull the jig saw plate down harder  and occasionally thru the plastic protection sheets.
  I ended up using one of the band saws.. but these where flat sheets.
 The 4" grinder with a thin abrasive cut off blade melted as it 'cut.. causing rather unsightly dags... but these broke off very easy and a quick touch to the edge made good.
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 1:55pm
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"You think if had a bit of over hang on the outside of the mould, that extra 1/2 to 1 inch may not bend down well  , tidy as what is inside the mould?"

I don't see the 'overhang' edge as any different to my template edge as far as bending goes. Should bend to the same profile. Just that you have more to bend and then have to cut the profiled edge. The template really didn't know there was a matching profile below it. It just went where I told it to go and I used the old screen below the sheet as the roadmap. Having another 1/2'' following  the profile of the bend shouldn't make any difference.
If you can surmount those issues (two heat guns and a few test cutting runs) your method should work fine and guarantees you will get a correct profile and fit at the end. With a bit of homework prep - def worth a shot. You won't have to sweat whether the final product will be a correct size. Too small worse than too big.
Regards
Alan 
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Post Options Post Options   Likes (0) Likes(0)   Quote Alan L Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 2:06pm
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There are proper perspex cutting blades (skill saw). They have zero rake on the teeth.
If for instance you could get such a thing for an angle grinder you could support the outside edge while cutting.
Alan
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Post Options Post Options   Likes (0) Likes(0)   Quote ofthesea Quote  Post ReplyReply Direct Link To This Post Posted: 05 Mar 2021 at 3:56pm
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Damn impressive anyway
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 06 Mar 2021 at 9:46am
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This should be made a sticky post somewhere.
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