Beam connection

[Raf]

Hi all. I am looking to buy a Wharram 30' to 36' and found a couple I can afford however, the design doesnt  seem correct to me, where the beams connect to the hull. Here are 2 pics of a 36' Tangaroa.

My question: is these set up, standard to the new Tangaroa design or was modified by the builder?

Thank you

[Robert Hughes]

I tend to agree with Galway Bay here.  The key is to have a controlled amount of flexibility.  If you want to make a structure rigid you have to design it rigid and accept the weight penalties.  If you just stiffen one bit you tend to transfer the loads to the bit that it was connected to, so that bit needs to be beefed up as well, and so on.

On Wharrams the inbuilt flexibility doesn't normally cause problems with the rig, because most of the rigs are designed with low aspect ratios and (relatively) low stresses.  Very few use rigging screws.  If you replace a Wharram rig with a high performance high aspect bermudan rig you might well run into difficulties due to the boat flexing.  Horses for courses...

Speaking as a mechanical engineer, very many engineered structures are designed with controlled inbuilt flexibility, such as bridges and aircraft.  Next time you fly in a jumbo jet try sighting along the wing as it takes off, or in turbulence.  You'll see the tip wags up and down by as much as ten feet.  If it was built rigid it would either snap or be so heavy it would never get off the ground.

Nature takes the same approach.  Try jumping off a small step, say 30cm high.  It doesn't hurt because your ankles and knees flex.  Now imagine doing it with your knees locked straight and feet flat, landing on your heels.  Without the flexibility your structure needs you'll do yourself serious injury.  Do not try this at home!

[Reuben Filsell]

Drill the holes oversize and then fill them with epoxy and glass with bolts in place, waxing the bolts before hand will allow them to be removed.

simple.