composite mast modeling (Uni proiect)

Hi,
I'm a 3rd year engineering student at the uni of newcastle. I'm trying to model the carbon mast on my VS (a 15 foot performance skiff). I have access to strand7 and pro-engineer and would appreciate any help or sugestions concerning the calculating the forces from the sails and modeling the carbon laminate layers.
Thanks

 

Get yourself a copy of Principles of Yacht Design. They have a whole chapter on rig design. If you are an engineering student you will be able to pull out the beam bending theory from the equations given. The safety factors are already applied in some of these equations as well, which makes it a little difficult. If anything, it will give you an idea of what forces you are looking at and how they calculate side forces and compression.

It all relates back to mechanics and the mechanics of beams, i.e. deflection, buckling .... If you can find the section modulus then your on your way to building the correct mast section. Computers are useful for finding sectional areas and shape and FEA is great for modelling the spar to get the lightest composite possible within your design needs.

Good luck with it. Personally I find rig design one of the more challenging and interesting areas of design. Cheers.

 

Stress Analysis of Fibre-Reinforced Composite Materials by Michael W. Hyer is a reasonable text.

It should be possible to model the sail on the mast and boom using the pressure distributions from the text mentioned before. You will need to add in vang and main sheet loading etc. Make sure you run it non-linear.

Dave

 

Using Strand7 for this project will help you out a lot. It has a few features that you will find useful. I have used it for a number of years in the engineering world as well as a little bit for sailing things. Here are some of the things I have found out.

One feature you will find useful will be the laminate feature. Basically it will bet you define a laminate as a series of plies. You define the individual plies and then give strand the thickness of each layer. It will then form an orthotropic plate that has the matching properties for this laminate. It does limit you to having a linear material property type however that is not such a big issue as most composite materials respond elastically to fluctuating short term loads.

You will however need to run the model for non-linear geometry. You should use the non-linear geometry solver with both the non-linear geometry and “include KG” options checked. Have a look through the strand 7 help files for an explanation of these terms.

Do not try to model the sail and apply the loads to the sail. Work out the loads the sail puts into the mast and only model the mast and rigging. The reason I say this is that the sail fabric is technically a mechanism. It relies on a whole range of tensions to actually maintain the shape. Getting all these tensions right in the model is very difficult. Further though Strand7 is good, it is an implicit solver and cannot cope with a high degree of non-linearlarity. Model up a simple I beam cantilever out of plates that is slender and load it until it buckles in a flexural torsional buckle. The analysis will diverge when the rotation exceeds only a few degrees. Fabric structures are usually modeled with a dynamic relaxation type solver.

Model the geometry of the mast in pro engineer and import it as an iges file into Strand7. You can then use the automesh feature to create the mesh. Be careful to align the local plate element axies as that will affect the laminate directions.

If you have any queries post back here and I will answer them if I can. Or post the model so I can have a look at it.


Nobody.

 

thanks guys

 

Yes, I agree about not modelling the sail.

You will need the composite design add-on to Strand. It is quite expensive.

Dave

 

how can i find section moduls of composite yacht.for stell yacht it is possible..is there any document about it.