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Old 07-21-2013, 07:48 PM   #1
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Weekend Venturi Project

Over the past year, Skinny Dippin's venturi windshield deteriorated quickly. It's always been a poor fit as the PO just got a friend to do it and must have told him to do it on the cheap. The plastic was a mere 1/8th" thick and of the 36 screws used, there must have been 10 different sizes used. It was deep yellow and looked like crap. At idle, the thing rattled around and made a heckofa racket. It was time to change it out.

Pics of the old:


IMG_1755 by GonzoF1, on Flickr


P1020250 by GonzoF1, on Flickr

I found a local (Morrisville, NC) source for Acrylite GT at 3/16" thick and hunted down a local waterjet cutting company. I wasn't comfortable trying to rig my woodworking tools to try and cut the weird angles or hope I could make them straight with a jig/scroll saw. Waterjet seemed like the best option.

The hard part was coming up with super-accurate measurements to give them. The previous one fit so poorly, I had a lot of on-the-fly adjustments to try and improve the fit. And these parts are neither square or identical from port to starboard. Finally, after a bit of experimentation, I found it only took two screw sizes to do the whole job with nice little acorn nuts to give it a factory finished look.

The whole acrylic job... Materials (4x8 sheet and cutting) set me back only $225. Screws and hardware came in at another $100. Nice.

I was sweating like a whore in church hoping the measurements were correct and it would all go together correctly. History as the barometer would say that I would be headed back to Cary... disappointed... dejected... and would have to fork out another $225 bucks for a re-cut.

However, things could NOT have gone more smoothly. Every piece fit like a glove, and other than drilling a 3/16 hole in my middle finger on the very first hole of the project, I am 98% happy with the results.

Hope this help someone in the future.

Project completion pics:


IMG_2273 by GonzoF1, on Flickr


IMG_2267 by GonzoF1, on Flickr


IMG_2241 by GonzoF1, on Flickr


IMG_2239 by GonzoF1, on Flickr

Thanks for your time!
Tom-
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Old 07-21-2013, 08:12 PM   #2
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Looks good, Tom. You've sure got a lot of venturi windshield around your FB. Looks great and a reasonable price for all that material. Imagine what you would have spent if you hired someone to do the same job.

Did you need to use any rubber grommets to isolate the WS from vibration induced cracking? I've got a couple of cracks emanating from the screw holes and have thought about using rubber washers or bushings next time to prevent the cracking.

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Old 07-21-2013, 08:27 PM   #3
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Actually, my research with the plastics companies revealed the main cause of cracks like that are from expansion and contraction from temp changes. Drill the screw holes too small and when the materials change size in the temperature swings, cracks happen.
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Old 07-21-2013, 10:24 PM   #4
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Looks good, Tom. You've sure got a lot of venturi windshield around your FB. Looks great and a reasonable price for all that material. Imagine what you would have spent if you hired someone to do the same job.

Did you need to use any rubber grommets to isolate the WS from vibration induced cracking? I've got a couple of cracks emanating from the screw holes and have thought about using rubber washers or bushings next time to prevent the cracking.

The grommets are a great idea and would be great in places that endure vibration. But the vibration from the engine is not likely to make it to the flybridge. I would definitely use them in areas closer to the vibration source.
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Old 07-21-2013, 10:49 PM   #5
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Drill a little oversize and don't tighten all the way...nylock nuts won't back off if not tight.

Check with polarized sunglasses for stressed areas and redo with larger holes or less tight.

Not to say rubber grommets wouldn't work either.
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Old 07-21-2013, 10:51 PM   #6
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But the vibration from the engine is not likely to make it to the flybridge.
Oh heck yes it does! One of the main reasons I wanted to change it to a thicker material is because the engine vibration made it rattle like crazy! On our 35' boat, every engine vibration makes it to the flybridge. Even after just a few years of ownership, I (and especially Bess) can feel many nuances about how she's running through our feet and by listening to the hardware noises

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Old 07-21-2013, 10:54 PM   #7
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The grommets are a great idea and would be great in places that endure vibration. But the vibration from the engine is not likely to make it to the flybridge. I would definitely use them in areas closer to the vibration source.
Seriously?
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Old 07-22-2013, 07:08 AM   #8
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Drill a little oversize and don't tighten all the way.
Ooops... Perhaps I will back them off a little next weekend. Thanks for the tip, Scott.
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Old 07-22-2013, 07:40 AM   #9
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Ooops... Perhaps I will back them off a little next weekend. Thanks for the tip, Scott.
Every time I'm up there with my sunglasses on...I say hope that doesn't crack till I get around to loosening it a tad more...
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Old 07-22-2013, 07:56 AM   #10
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hahaha! Well, I *did* taper all the holes with a countersink bit to prevent cracking. That should help some too. I hope ;-)
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Old 07-22-2013, 08:40 AM   #11
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Greetings,
In a previous life, I had occasion to work in conjunction with a tool and die maker who was tasked with making a quite complex piece of apparatus out of plastic (can't remember whether Plexi', Lexan or what-ever). The end user wanted a piece free of stress/strain. Even the drilling/machining of a simple hole imparted stresses in the plastic (observable with a polariscope). The equipment used (polariscope) was only capable of measuring qualitative amounts of stress NOT quantitative amounts so the actual AMOUNT of stress was unknown BUT there was stress in the piece.
So, IMHO, there is the potential for crack development around ANY hole one may drill in plastic. I am unfamiliar with water-jet technology, so THAT may create a stress free piece.
Mr. Tom. NICE looking improvement!!
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Old 07-22-2013, 09:25 AM   #12
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True, however, the waterjet guys told me they would cut the perimeter, but would not cut "holes" (eg: mounting holes) because the waterjet wanted to blast the acrylic apart. Because of the tweaking that needed to be done on the install, I had plans from the beginning the drill my own holes. But because of your post, RTF, I thought it was worth noting :-D
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Old 07-22-2013, 07:49 PM   #13
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Quote:
Originally Posted by Tom.B View Post
Oh heck yes it does! One of the main reasons I wanted to change it to a thicker material is because the engine vibration made it rattle like crazy! On our 35' boat, every engine vibration makes it to the flybridge. Even after just a few years of ownership, I (and especially Bess) can feel many nuances about how she's running through our feet and by listening to the hardware noises

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Seriously?
Well, you can't be running one of these on the flybridge while under way and blame the vibration on the engine!



Kidding aside, I'm drawing upon my own experience mostly. I have the infamous king of vibrating small Diesels: the Perkins 4.108. I often sit on the flybridge if I need a break from the vibration. And up there, it is peace and tranquility times 100 compared to the lower helm.
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Old 07-22-2013, 09:00 PM   #14
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Well, you can't be running one of these on the flybridge while under way and blame the vibration on the engine!



Kidding aside, I'm drawing upon my own experience mostly. I have the infamous king of vibrating small Diesels: the Perkins 4.108. I often sit on the flybridge if I need a break from the vibration. And up there, it is peace and tranquility times 100 compared to the lower helm.
Yes... but an engine will certainly send vibes on smaller boats to the bridge.....

ps...your pic didn't come through on my computer...
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Old 07-22-2013, 09:18 PM   #15
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Yes... but an engine will certainly send vibes on smaller boats to the bridge.....

ps...your pic didn't come through on my computer...
I received a message indicating the mods must approve the image before it can appear. I had pasted a link from an image search. Based on the low number of posts I have, it's completely understandable and I fully respect the safeguard. It was an image of one of these:

Name:  vibrating plate.jpeg
Views: 393
Size:  15.0 KB

Personally, I like the one above much better than the original one I posted This one is heavy duty commercial grade.
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