19M frp passenger vessel thickness of laminate

Discussion in 'Boat Design' started by mizkuzi, Dec 14, 2019.

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mizkuziJunior Member

Hi to all frp experts,
I have a lamination schedule of a 19m passenger vessel with stabilizer (not my design & has not been built yet) then I am trying to re compute its frp scantlings & lamination thickness using classNK.

The plan lamination is using a 25mm PVcell foam core 130kg/m3 density laminated by 2layers of BX600 in & out.

The purpose of my computation is to check if the lamination is enough for this length & type of vessel. My results tells me the shell laminates inner & outer should not be less than 4mm. Am I correct? And should i just use BX600? Ive read that WR is good for impact strength & CSM to build thickness.
I am not going to build this boat. I am just practicing calculating frp scantlings for my own benefit of understanding how to pick the right thickness and laminations for passenger types of vessel coz I want to learn more.
Advice from experts of frp scantlings will be highly appreciated by an amateur like me. Thank you very much.

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bajansailorMarine Surveyor

Will the foam core be in the topsides only, or in the hull bottom as well?
Will it be a fast / high speed vessel, or is it a displacement hull form?
If a high speed vessel, what is the desired service speed?

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mizkuziJunior Member

Hi sir, foam core in hull bottom is with 4layers of WR600, 2inner & 2 outer. Ive read WR is not good without CSM applied. then on top sides uses 4layers BX600, 2layer in & out. Design speed is like 14-16kn, its a planing hull. Passenger estimated to be 30-50 pax. This will be a trimaran type.

Can you pls give some advice? Im not yet good in scantlings computation though.. I just want to make sure if the hull wont break with this schedule. Thanks a lot!

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mizkuziJunior Member

Also, with regards to joining the panels, is it ok to use only 2layers BX600 with 50mm overlap?. Or which type of glass is best for joining? Thanks!

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TANSLSenior Member

Maybe I am getting something wrong but I wonder why do you need to join several panels?. It is normal to make the hull or deck with continuous laminates, although not uniform, so that there are no individual panels but continuous surfaces.

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bajansailorMarine Surveyor

When you said 'with stabilizer' I thought you meant an internal stabilizer like a gyro or adjustable fins.
But I see that you are building a trimaran - it could be called a stabilized monohull.
If the main hull is relatively narrow (ie much more than a L/B ratio of 3, which is a rough average for planing boats) then for a speed of 14 - 16 knots it might well be still in displacement (or semi-displacement) mode, rather than 'planing' as such. What is the maximum width of the main hull at the waterline?
Can you post any sketches or drawings of what you have produced so far?

Re your BX600, this appears to be a type of stitchmat -
[Hot Item] Bx600 Fiberglass Biaxial Fabric Fiberglass for Composites https://utekcomposites.en.made-in-china.com/product/JjqxkasPHmWN/China-Bx600-Fiberglass-Biaxial-Fabric-Fiberglass-for-Composites.html

WR600 also appears to be a type of stitchmat -
[Hot Item] Glass Fiber Combo Mat Wr600/M450 https://tianmagroup.en.made-in-china.com/product/LjTJnrYhBEcA/China-Glass-Fiber-Combo-Mat-Wr600-M450.html

When you mention 'WR is not good without CSM applied', yes, it is good practice to have CSM between layers of traditional woven roving when doing a 'conventional' lay-up. I think it would also be useful to have a layer of CSM between layers of stitchmat.

Are you definitely having foam core below the waterline as well?

Re your stabilizing outriggers, will you be building them in similar fashion?

Last edited: Dec 16, 2019
7. Joined: May 2011
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mizkuziJunior Member

Yes bottom hull is also with foam core. Is that ok though? Or its not advisable? Could you pls take a look on these & give me some idea if the lamination sched is fine or you think its kinda weak? (Can iijust send through email my screenshots? I have it saved on phone but dont know how to post pics here coz I dont have URL for the image. Outrigger will be of same specs with foam core.

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mizkuziJunior Member

L-19.41m
Max Breadth incl. outrigger 8.40m, depth, 2.50m,
Draft 0.80m

Yes foam core below WL, is it not advisable? Outriggers same specs with foam core. Or pls tell me what is advisable.

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bajansailorMarine Surveyor

Mizkuni has emailed some photos of his design and the specifications for it - I will attach them here.

I do not know enough about fibreglass scantling design to be able to comment with assurance, but I know that others on here have a lot of experience and will be able to offer good opinions.

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mizkuziJunior Member

Thank you bajansailor, hope to get some inputs from experts

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