groper
Senior Member
- Joined
- Jun 18, 2011
- Posts
- 2,507
- Reaction score
- 175
- Location
- australia
Thanks adhoc, last post was very helpful.
All of the sandwich panel failure modes such as buckling, skin wrinkling, crimping, and more, have equations for checking located in here -> http://www.hexcel.com/Resources/Dat...eets/Honeycomb_Sandwich_Design_Technology.pdf
Checking these with the current scantlings we know already work, all seems to be ok, as you would expect.
The yachts im referring to have already been built, and have been for many years, and have NA stamp of approval. The changes im looking to make, is simply the method in which the stiffeners and frames are installed into the boat - mainly to reduce labour and time. Cost is not such an issue - if it were, they would not be built using expensive cores and epoxy resins etc. I suspect everything is glass taped, simply because nobody has really looked at the problem in detail, theyre just doing what they know works -as tunnels would do, and like ive said before, theres nothing wrong with it... well nothing except for the time it takes to build it with those methods... i have a different approach to building, using different methods than most people use, being able to bond rather than tape will make a huge difference to me, but perhaps no help at all to someone else who is building with different methods.
So the main focus is not what the laminates, spacings, sizes of stiffeners are as we already know these...same goes for the laminate E, we already know it. but rather constrained strictly to the bonding / joint areas of these transverse and longitudinal stiffeners, and whether or not we can eliminate the over laminate fibreglass tapes in the bond fillet areas. We may have specialized adhesives with enough mechanical properties to get the job done without it. Considering the loads are relatively conservative, were only dealing with maximum displacement vessels of around 6000kgs and speeds not exceeding 25kts. Forward hull bottoms have very small area, with steep deadrise angles, and yachts cannot sail directly to windward, so slamming pressures are kept low organically. Not sure what class would say about the above reasoning tho, i havnt read through the slamming pressure calculations yet.
Brian, i have no desire to try Nomex honeycomb core, which seemed to be the issue Nigel Irens was referring to... i dont beleive its the right core material for building boat hulls, its also not compatible with my infusion process. It would have a place in other areas of the boat however, many use it for furniture panels, and other structural stuff. I think ill stick with foam, in varying densities, depending on required application - Im using 300kg/m3 in my current transoms as well as other highly loaded areas where you would normally find a plywood core for resistance to crushing and through bolting etc. I find foam is very user friendly to build with and the methods i use.
All of the sandwich panel failure modes such as buckling, skin wrinkling, crimping, and more, have equations for checking located in here -> http://www.hexcel.com/Resources/Dat...eets/Honeycomb_Sandwich_Design_Technology.pdf
Checking these with the current scantlings we know already work, all seems to be ok, as you would expect.
The yachts im referring to have already been built, and have been for many years, and have NA stamp of approval. The changes im looking to make, is simply the method in which the stiffeners and frames are installed into the boat - mainly to reduce labour and time. Cost is not such an issue - if it were, they would not be built using expensive cores and epoxy resins etc. I suspect everything is glass taped, simply because nobody has really looked at the problem in detail, theyre just doing what they know works -as tunnels would do, and like ive said before, theres nothing wrong with it... well nothing except for the time it takes to build it with those methods... i have a different approach to building, using different methods than most people use, being able to bond rather than tape will make a huge difference to me, but perhaps no help at all to someone else who is building with different methods.
So the main focus is not what the laminates, spacings, sizes of stiffeners are as we already know these...same goes for the laminate E, we already know it. but rather constrained strictly to the bonding / joint areas of these transverse and longitudinal stiffeners, and whether or not we can eliminate the over laminate fibreglass tapes in the bond fillet areas. We may have specialized adhesives with enough mechanical properties to get the job done without it. Considering the loads are relatively conservative, were only dealing with maximum displacement vessels of around 6000kgs and speeds not exceeding 25kts. Forward hull bottoms have very small area, with steep deadrise angles, and yachts cannot sail directly to windward, so slamming pressures are kept low organically. Not sure what class would say about the above reasoning tho, i havnt read through the slamming pressure calculations yet.
Brian, i have no desire to try Nomex honeycomb core, which seemed to be the issue Nigel Irens was referring to... i dont beleive its the right core material for building boat hulls, its also not compatible with my infusion process. It would have a place in other areas of the boat however, many use it for furniture panels, and other structural stuff. I think ill stick with foam, in varying densities, depending on required application - Im using 300kg/m3 in my current transoms as well as other highly loaded areas where you would normally find a plywood core for resistance to crushing and through bolting etc. I find foam is very user friendly to build with and the methods i use.
