Boom timbers spliting after shaping?

[Steveh]

Here's a problem I experienced after shaping my boom.

The stock sat round on the shed floor, on spacers, for several months (in the way).
I cleared the shed in preparation to move Ngatira out of the shed and was faced with a nice working space to shape the boom. Squared it up with tapers and then eight sided it and left the boom sitting on horses for a week.
http://farm4.static.flickr.com/3121/3252026201_e421ec7b2d.jpg
http://farm4.static.flickr.com/3413/3252851396_f00cff568a.jpg

Skill saw method of removing corners... and
http://farm4.static.flickr.com/3087/3252026751_e142d09f21.jpg

traditional way by draw knife.
http://farm4.static.flickr.com/3531/3252851604_0bb482d1db.jpg

http://farm4.static.flickr.com/3070/3252851704_b25126b775.jpg

http://farm4.static.flickr.com/3423/3252851772_e27275bf33.jpg

The temperatures can get high while it's closed up and over the course of a week the timbers split badly longitudinally.

Was this from the heat or was it from tension in the timber?

Unfortunately I deleted the shots of the cracks but needless to say they resembled canyons!!

I have since oiled the ends with linseed.

[Pernicious Atavist]

Sure looks like continued drying due to the heat and lower humidity. Same thing happened when the new owner of my skiff took better care of it than I did! Others will wade in here, I'm sure, with reasonable fixes. 'Luck!