Composite High Speed Boat Structural Hull Bottom Grid

Greetings from France I thank you all for your most kind and very useful feedback ! I am now preparing to go today to La Rochelle Boat Show Le Grand Pavois .
The task at hand is quite particular I am to plan for , design and build a short series of the high speed boat a batch of only 10 boats.
The topics is precisely how to think for and plan for the custom and semi custom boat building where the cost of tooling does matter.
As we speak my design of sport motor boat is being completed nearby Hong Kong. The Taiwanese company nearby Hong Kong also did plan for choose the approach to the building of structural framing as for a short series because they do not know how many boats they will sell. In this case the hull and deck and cabin were built in molds and the structural framing has been built on polyurethane formers laid by hand and hand lamination over them. This approach to building of the hull structural stringers is not good enough for the boat I am now planing to build here in France because the pressures on the bottom of the high speed stepped hulls are much higher and the weight control needs to be better>
here in France I am thinking about making the structural members out of flat composite panels we are to make on table and then fit and join on the hull bottom with tabs the longitudinal stringers would be reinforced on top with monoaxial like the image I posted above.

 

Table production is very slow for a batch of ten boats. There is just so much cure time involved taking up the table, requiring edge trimming, assembly, tabbing. I know a lot about table production and it is not at all fast. Be very careful assuming so..

It isn't always the table that is slow, but fairing later...

 

Here is a link to Andrei's Facebook page - you can view it without logging in as such.
Log into Facebook https://www.facebook.com/fiftyboatdesigns

And a wee animated video of the Artemis 40 mentioned above.
Log into Facebook https://www.facebook.com/fiftyboatdesigns/videos/898021667813338/

And a link to the Artemis range of Selene Ocean Yachts - but no mention of your 40' yacht?
Artemis - Selene Ocean Yachts https://www.seleneoceanyachts.com/artemis/

 

The grid can be infused in place over formers, either after the hull is done, or as a one shot infusion together with the hull.
Management of the production processes is highly dependent on the manufacturing location specifics, there is no universal best answer.

 

Hi @bajansailor thank you for your feedback with the links to my FB page greetings from France! The Artemis 39 sport motor boat is as we speak under final construction stages following 2.9 years work on the prototype through the challenging economic period of the global pandemic . The Taiwanese company Selene Ocean Yachts is targeting the the sport boat to thir own China and South East Asia markets to start with ; and this is why they decided to build the structural stringers of the first boat according to China Certification Standards. They do plan to build the further units of the boat as per EU ISO Strandards. They will soon do the sea trials of the prototype and the sport boat will be on their website. At present I am in France designing the high speed sport boat and the large motoryachts for a France yacht company in the area of Bordeaux

 

@Rumars and @fallguy Greetings from La Rochelle Le Grand Pavois Boat Show thank you for your feedback !
I do fully agree 'The grid can be infused in place over formers, either after the hull is done, or as a one shot infusion together with the hull.
Management of the production processes is highly dependent on the manufacturing location specifics, there is no universal best answer. "
Yes we did here in France the infusing in place over formers as a one shot infusion together with the hull.
At present I am trying to determine however if the grid is efficiently buildable in other that tophat stringer profiles namely in square section flat made on marble prefabricated fiberglass composite panels that would be 1. cut by CNC and 2. bonded in place with fiberglass overlays as the attached image The boat bottom stiffener & details design flow charts looks like this attached and starts with the calculation of the slamming primary and secondary loads to wich the boat is to resist for the speed of 55 knots followed by the calculation of stiffener moment of inertia and of the stiffener section modulus.
I observe the typical motorboat bottom stiffener grid is designed and built of transversal frames and of either 3 longitudinal stringers or 4 longitudinal stringers or even 6 longitudinal stringers ( of tophat section ) .
This indicates it may be achievable to design and build high speed bottom structural grid made of high relatively thin panels like these panels in the image here wich are carbon face over inner PVC core
Perhaps instead of 4 longitudinal bottom stringers is it possible to think 6 longitudinal stringers ? [/ATTACH]

 

Here is typical of PERT Flow chart in Excel. MS project is similar but more complex. Familiarize yourself.

Distinct work process are in boxes and designates the number of man allowed to work on a single shift (8 hours/day, actual 7.5 hours). Nodes are marked in green for every distinct process. Summing junctions are marked in red when two distinct process merge and join.

Manpower are allocated for every work process. Number of men will vary depending on the number of days allotted to finish a part.

This is also a line balancing program. There must be an even number of men (not half a man) total for everyday to make sure the men you hired are not idle at any given day. Case in point is Curing time when the men are not doing anything allowing the part to cure which can last for 24 hours. Note glitch in the arrangement (curing).

You may adjust the number of man for a given productivity rate your man is capable depending on his skill set.

Critical Path Method (CPM) is another subject when you have to determine if you have to "crash" a project (shortening the total number of days) or you have to "squeeze" a node because the time allotted is slacking and may need to work overtime or change the method. You have to find where the project is causing a "bottleneck" and or justify the means.

Note that this is just an overview and I am working only from memory the best I can remember.

 

Thanks for the flow chart your feedback is very useful Greetings from the Grand Pavois La Rochelle

France

 

I am sure it's entirely possible to design a grid made from flat plate. The question is what do you gain by it? Weight savings will be minimal if at all. Work hours will be significantly increased.

 

The problem with grid layout whose stiffeners are all the same height to support the floor is continuity. It is discontinuous where it crosses.

Scantling rules says one supports the other. In a transversely framed boat, the longitudinals are continuous. In longitudinally framed, the transverses are continuous.

In a grid, all corners should be connected to each other by a web or a box to maintain rigidity.

I prefer a thin female mold reinforced by steel frames. That way, all surface will be level to accept the deck. The plug can be made out of wood, fitted to a finished laminated hull.

 

@Rumars thank for your feedback. 1. The structural framing is one of the most time and money consuming parts of building a composite leisure boat. 2. The cost of the framing grid can be higher than the hull mold grid . 2. In regards labour and time the intricacies of the structural grid make it time consuming to lay the fiberglass fabric properly 3. the deep and relatively narrow longitudinal stringers concavities on the bottom grid mold are prone to imperfect lamination.
I calculated the surfaces the hull surface is 70 square meters. The structural grid surface is 72 meters. The cost of these two molds is therefore quasi similar and at a level of tens of thousand of EUR
The lamination of the structural grid apears to take twice the time and cost of the lamination of the hull due to its intricacies
In those contries where the 5 axis CNC is not available the hull mold can be made by hand but the bottom framing wont be feasibe by hand it is too time consuming
If we think bottom framing structural grid cost purely theoretical about EUR 20000 it appears makes sense to think those money can well go into the lamination on marble and extra labor of joining together and the structure of the short series 10 boats in 2D CNC cut flat panel made in house in our own boatyard

 

@rxcomposite, thank for your feedback. Yes I do agree with you. I am thinking my hull laminate to be sandwich composite . I found an interesting paper writen by a Swedish Masterand thesis discussing the advantages disadvantages of sandwich composites versus the single skin composites in the Kokum Sweden . This paper makes mention of a software RSTRUCT program is a design tool that facilitates improvements in the structural design of a high speed light craft in compliance with the rules of DNV. I think the DNV Rules are not far from the ISO 12215 . The program, which is written in Matlab and has a stand-alone interface , gives instant and graphical feedback of how well the structural elements are utilized, with respect to stiffness, strength and minimum criteria according to the DNV rules. This facilitates performing iterations in the design spiral resulting in a closer-to-optimal structural arrangement . Does anyone know where to download this RSTRUCT software ?????

 

Wow. That expensive over there.

Before I forget, ISO rules on construction limited to less than 50 knots. Review the first part of the rule. ISO 12215-5, Part 1, Scope.

 

I use LR SSC rule (comes with a software) or DNV GL. LR has a steep learning curve and is expensive.

 

We used structural grid mold in one of our project, an 8 meter cat. It is very fast to fabricate and mold. Intricate, yes, but once the mold is done, it is very productive. Just drop and insert wet CSM.

We still use male wood mold for short run production or one off. We laminate a former, tab it to the hull, then laminate over it. Labor consuming but labor is cheap here.