Aluminum mast from thin wall vaccum tubing

Sparcraft 67 is around 2 mm

Sparcraft FM-67 Mast https://www.rigrite.com/Spars/Sparcraft_Spars/FM_Masts/FM-0067_mast.php

 

Sparcraft S67

82 x 118 mm
ca. 2 mm

67 cm^4 XX
128 cm^4 YY

2.2 kg/m

Selden C126

79 x 126 mm
ca. 2.4 mm

74 cm^4 XX
172 cm^4 YY

2.5 kg/m

 

The Selden C126 is used in 8m boats. The OP is talking about an 11m boat.

 

I never said that it was for an 11 m sailboat! It is actually for an 8m sailboat with an 11m mast lenght.

 

I actually got a quote for a Z-Spar Profile Z265 including boom, spreader, stays amd schrouds, the qulte was 18 000$CAN!!!!

 

There is no reason not to make a mast from common round tubing providing you want a round mast. What you need to watch out for are the technicalities: tube alloy is important, prevost for example only uses 6060 and 6063, you have to base your calculations on the specific alloy you will be buying. When splicing the sleeve needs its end cut in a specific way (fish mouth or darts) in order to avoid a hard point stress riser, that lenght (minimum one diameter at each end) needs to be added to the sleeve, fastener holes have to be staggered to avoid zipper effect. Thin wall tubing needs rivets not screws. If glueing you need to respect the manufacturer indications to the letter and select the appropriate product (elongation is important because the mast bends).

If you want to compare prices you need to do it for the bare extrusion, a complete mast has many other parts and many hours of work included in the quote.

 

My apologies, I read that completely incorrectly.

 

You can get an aluminum round tapered light pole for about $1,800. There are sometimes surplus poles available.

 

OK, Gonzo made me think more and I looked again at light pole. The issue I had with light pole is that it is too heavy for my purpose, the wall thickness is around 0.159 in for a 35 ft mast. I was thinking of how I could shed weight away and came to think that maybe I could sand it or machine it to get down to around 0.083 in think. Basically I want the mast to be around 3 kg/m.

While I was reading ''Principles of Yacht design'' (very good and interesting book and recommend it to all the enthusiast) p.189. in the section talking about ''means of reducing mast disturbances'. Basically the concept is to add roughtness to a round mast to create a turbulent boundary layer around the mast to keep the flow attach longer to the mast, as I understand it is very similar concept to the golf ball dimple effect.

Basically, I could greatly reduce the light pole mast weight by adding routed longitudinal texture to the mast and at the same time improving aerodynamic of the round mast. You can see the attach drawing to see what I am talking about. The view are from the top of the mast and the top mast.

The weight reduction is substantial, initially the mast is more than 110 lbs and after the machining it should be at just barelly 80 lbs, more than 30 lbs less.

 

Aluminum alloy at T6 temper is hard to machine. What is the difference in center of gravity between the thicker tapered pole and the straight aluminum tubing? That will make a difference in stability if that is your concern.

 

I question the wisdom of working from what might be cheaply available and hoping to make a mast from it.Much wiser to work from a summary of what the mast will need to provide and then find a piece of metal that will work.Machining all those neatly spaced grooves won't be easy or quick and it might be a good move to check out trip turbulators as attaching a pair to the blank tube would be less work and very likely as effective.

 

There is nothing cheap about 6063-T6 aluminum light pole. The alloy is of good quality as good as the aluminum from a sailboat mast manufacturer!

The price difference is mainly due to volume, how many light pole are extruded a year versus how many sailboat mast are extruded! Light pole are extruded by the million a year and sailboat mast probably by the thousand!

The main issue is the weight of the light pole, they are much thicker than what I would like for the final weight of the mast. Very crucial to preserve a good righring moment.

 

Yep. Eons ago I got a similar-size mast from an Etchells for a few hundred bucks. It had broken at the deck but a splice fixed that and I still have it. Old Etchells masts are cheaper these days. A J/24, Etchells etc stick that has been damaged or aged would be an easy and cheap fix.