LB26

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fallguy1000
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Re: LB26

Post by fallguy1000 »

Prime the whole boat to the rubrail.

As for the rest, up to you, but priming now is easiest.


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TomW1
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Re: LB26

Post by TomW1 »

Yes prime the whole hull to the rub rail now and finish only the bottom with the final bottom paint. Well good luck. Tom
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les2021
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Re: LB26

Post by les2021 »

Afternoon Boat Builders

Dan / Tom Thanks for the input on painting the hull. I will come back to this subject later if thats ok, trying to locate suppliers at the moment !!!

Today I want to raise the old swim platform debate !!! I am about to commence work on the platform so thought I would see if anybody had any advice before I go mad building.... This is based on the old Reefie thread and his ideas.

My idea is to laminate a spreader band around the transom, 2 layers of M200 / 2 layers glass. This I hope would spread the impact point if it should happen.

The platform would be 3 layers of M80 with a 45mm M200 ring beam band around the top to take the 9mm Marine Deck finish, the 45mm band will have reduced outlets to allow for the water to escape as the platform will have a 10mm fall.

The brackets will be 2 layers M80 / 2 layers of glass. I am planning 3 brackets, 1 centre and 1 each side 570mm from the C/L the ends will be picked up from rails that will travel 600mm along the topsides.

The last debate was on how strong the platform should be, should it break away if impacted so as not to puncture the transom. My transom is made up using M200 high density and I am planning 2 knee braces to add a little extra strength.

So guys have I put the cat amongst the pidgeons again..... I have attached a drawing.

Cheers

Les
2d63f73e-d41b-4bfb-8de0-12c41f433dd0.JPG

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Jaysen
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Re: LB26

Post by Jaysen »

Adding to the things you want to consider…

I’ve been working at a marina. A large number of boats smash the swim platform into the dock when departing. Consider angled corners to allow easier exit from docking.

The boatyard services say this is the #1 repair they have to do.
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Re: LB26

Post by fallguy1000 »

Before I critique construction, have you considered stairs?

In the US, we have a boarding requirement that a single operator must be able to get back onboard.

some transom step ladders mount under, some mount on, and some mount into

Until you know the ladder, I'll reserve comments because the ladder needs hardpoints and enough dimension to support the plan.
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les2021
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Re: LB26

Post by les2021 »

Hi Guys

Noted Jaysen.

Dan I was planning to use a Vetus Telescopic Platform Ladder or something similar.

Cheers

Les

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Re: LB26

Post by Fuzz »

I am not sure how you can build a bracket strong enough to do the job and yet weak enough to break off before harming the hull :doh: I would worry it might break off when I did not want it to. Think I would build it strong and take my chances. And like Jaysen said it is pretty common to bump the bracket pretty hard around the docks.

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Re: LB26

Post by fallguy1000 »

les2021 wrote: Mon Dec 06, 2021 9:05 am Hi Guys

Noted Jaysen.

Dan I was planning to use a Vetus Telescopic Platform Ladder or something similar.

Cheers

Les
Need hardpoints for the ladder.

Personally, I'd use the M200 and make the swim ladder removable. Make a step of M200 and bolt the platform on with 6mm bolts and cup washers. If the platform encounters any undue force like a neighbors boat driving onto it; the bolts should shear away from the platform, so the platform can be made with a calculated load rating. I can help with the calculations. Something like a rating of around 2000 pounds would be a good target, in my opinion. This means the bolt strength for 10 bolts is 200 pounds for each bolt. This can be easily calculated for 6mm bolts and the thickness of the bolting area.

Something like this...where the green is M200 and the yellow is the platform. You can calculate the shear ratings or close of the platform. I do not know how to calculate the shear of the platform with glass. But you can calculate the raw core shear ratings easily to get an idea.

JM might be able to help with the shear ratings with the glass.

But basically, you design the platform to fail by breaking down. The calculation might be more complex with brackets under the way you have drawn.

All a hair above my engineering abilities. You can also present the idea on boatdesign.net and someone might help you with the calcs.

I prefer the metal brackets underneath because you can design the bolts to shear versus an all glass platform that is not possible to remove for repair or painting.. if you put non-skid on it; you may want to unbolt for maintenance and painting on sawhorses every 5 years..
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fallguy1000
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Re: LB26

Post by fallguy1000 »

M200 is 428 psi shear.

So, a 1/4" bolt going through 1" is 0.25 sqin.

428 #/in * 0.25" is 107# to tear out, but the glass adds to it..

..consider it conversational..
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les2021
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Re: LB26

Post by les2021 »

Thanks

Dan / Fuzz

I'm am now and was then confused when I read the Reefie thread. Keeping it in mind I have owned a boat but never built one.....

I know all factory boats are different but many have platforms that are laminated direct to the hull so it all becomes one. This would suggest that there is a calc or method of building it as one with collision taken into account. Dan you mention S/S brackets surely these put more of a point load on the transom. If it takes a direct hit and the bolts shear and the platform flips up, what is to stop the object impacting your boat continuing and the point load of the bracket puncturing the transom.

My drawing of my proposed platform works along my way of thinking that.

The brackets are set back from the platform so the first thing hit would be the platform.
Putting the M200 double thick band across the transom would spread the impact, so if the platform was hit it would spread across the transom. The gap between the platform and the double band would only be about 5mm, this allowing if the platform should ever need to come off the lamination could be cut between bracket and platform.
Building the platform from M80 would hopefully allow it to break down ie dent/crush before anything more serious happened.

But remember guys these are only my thoughts I am a builder not a boat designer !!!!!

Jacques can you read the last 4 -5 post and give your thoughts please.

Back to you guys...

Cheers

Les

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