A Photo & Discussion Forum for Wharram Design Enthusiasts
Hi, I have recently purchased Hitia 17 plans #398. I am looking at the options for an aluminium mast as here in Australia, aluminium tube is quite cheap (wood/glass/epoxy would be more expensive, plus a lot more work). The H17 plans have the OD of the mast at 90mm/3.5" and per the Wharram FAQ, the wall thickness should be 1/8" or 3.175mm.
Problem is that I cannot find any tube at 90mm, only at 80mm or at 100mm OD, both at 3mm wall thickness, in 6060 T5. The 80mm weighs in at 12.7Kg and the 100mm at 16Kg, both in 6.5m lengths. So which should I choose? The narrower 80mm that is lighter? Or the larger 100mm that is heavier.
If I compare the H17 to the Tiki 21, which has a 102mm/4" x 3mm aluminium mast specified: The T21 has 19.25 sqm of sail, the H17 has 15.1 sqm (as per Rolly Tasker), so that is 78%. The H17 weighs 30% of the T21.
The 80mm tube would be exactly 78% of the OD of the 102mm, at the same thickness. Should be fine? I would just need to adjust the gaff fork to accommodate 80mm instead of 90mm, easy enough.
Does anybody know how much the H17 mast weighs, made from wood as per plans?
Well, my Hitia 17 mast was built to plan with two exceptions. It was constructed from Douglas Fir using birds mouth construction and it has an 18" extension x 2-1/2' diameter, because it's gaff rigged. Finished weight is about 29 lbs. Additionally, if your boat is going to be gaff rigged, the dimension for the gaff on the wing sail plan upgrade, is wrong. It will need to be between 80" and 81" long.
Thanks Omar, that heads-up on the gaff length is worth a beer, I owe you! I shall check the plans against the Rolly Tasker sail info. Nice effort on your mast, look good. 13Kg finished weight is awesome, just what I needed to know. Did you built the mast length to plan or did you make it taller, besides the extension for the gaff?
The mast height is to plan.
Wow, what a glaring mistake in the H17 plans: Sail head is 6'6"/1970mm, and the gaff is specified as 4'11"/1500mm. Maybe they meant to write 6'11", which would be 83"/2100mm, and close to your recommendation of 81". Thanks again for pointing that one out to me!
I'm pretty sure they just missed changing the gaff dimension when they repurposed the Tiki 21 rigging plan. You'll also need to draw out the gaff to reflect the 3-1/2" mast diameter. Also, much easier to do as a bent lamination than the method the plan shows. While I'm thinking about it, the widths given for the rear decks are also in error, much too narrow. Those are the only big errors, the other things I found, may be due more to technique, than design. On my hulls, bulkhead #2 needed a little more curve in the sides and top to be fair. I had the same deviation in both hulls.