A Photo & Discussion Forum for Wharram Design Enthusiasts
Hi - I need to replace my beams and prompted by this plan to make baot really trailerable eg replacing cockpit with netting.
- anyone any experience of aluminium beams - specifications/design?
- tube or maybe a box girder made of angle?
- anyone know who could specify this for me?
- anyone got a netting cockpit?
Of the varieties of aluminum, probably the best choice for this is 6061 T6. It is tough and forgiving, and fairly resistant to corrosion as well as to fatigue.
Personally I feel aluminum is about the worst possible choice for something of this nature. It is extremely reactive and subject to electrolysis and electrolytic corrosion. It also has a far shorter fatigue life than wood, so if there is any flexing and bending, it will eventually end up with fatigue cracking. Wood, if you choose quality wood and build well is the most reliable of all materials structurally. Choosing the right wood, and using the right construction methods and protection, matters of course. My personal choice for this kind of application would be good quality knot free close grain Douglas Fir.
I've worked with metals all my life, welding, fabricating, repairing, and engineering.
I am quite sure the 6 " beam mentioned refers to the fwd beam . Steve's (fiberglass) versions of the T 26 had, if i am not mistaken, the same two main beams as the "normal" wood -hulled T26's. 6"dia alu pipe seems in any case awfully small for a beam whihc not only holds the hulls together but is subject to the loads induced by mast & rig as well.
We built a Hitia 26 ( T 26 without the cabins, it's used as a day sailer, learn-to sail boat and camping cruiser) with alu beams . Boat is two ft wider then a standard T26. beam nr 1 is an ordinary 6" 4mm wall alu pipe. Beams nr2 and 3 were made of a salvaged mast of a 38ft piver trimaran whihc was wrecked in our bay . We did not bother with the dolphin striker on the mast beam. I do not think there will be much diffrence in weight between a wooden main beam and an equally strong alu beam. The standard nr 1 beam as designed by JWD on a 26 can, as seen, be replaced by an alu pipe and this does save a considerable amount of weight