Round Mast with golf ball texture

I want to make a 36 foot aluminum round mast for a gaff rigged sailboat. Most aluminum tubing found are just too heavy due to a thicker wall on what is available on the market

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.

The issue I had with using light pole for a mast is that it is too heavy for my purpose, the wall thickness is around 0.159 in for a 36 ft mast. I was thinking of how I could shed weight away to around 3 kg/m.

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.

Anybody tried textured mast to improve mast aerodynamic?

 

This reminds me of the time my Uncle Jim saw a kink in the reach of my trailer and said; that is bad; cuz it is a weak spot. We proceeded to hit a bad stretch of road and it broke.

Now, your plan is to do this with perfection in mind, but unless it is extruded; machining this has some risks of error.

 

You are 100% correct that it could be difficult to machine! But maybe with a setup and guide installed directly on the mast a simple router could be used!

I mighr try first with a small section of pipe to see if it is realistic to machine such groove!

 

Just forget it. Setting aside the machining difficulties, all you will achieve is a series of buildt in stress points when the mast is bending, nice crevices for salt to deposit and start corrosion, plus an imperfect saw to fray all your lines in a hurry.

If you want to increase your workload there's a better way. Build a carbon tube of the same weight as the aluminum one, at least then you can brag about it.

 

Honest question from a non sailboater who likes to dream of one day going to sea on something without noise...

In the system of a sailboat, is the mast that critical? What's the benefit from a bone stock standard mast vs a hyper complex super specialized one? How far out in the significant figures do you have to go to perceive a tangible improvement?

 

That could be a quote line for many things connected to boating.

 

As usual it depends. Masts can be treetrunks or high tech, depending on application. It's like the difference between a cast iron block with cast iron crankshaft vs. a magnesium block with forged and titanium everything and variable valve timing. One is heavy, not very adjustable with limited power, the other light, powerful etc. When done right both exhibit the same reliability if operated correctly.
From a aerodynamic point of view mast surface is probably the last thing to be addressed after you exhausted every other optimization possibility. On a gaff rig it's more for the owners mental well being then a real benefit, even high tech gaffs don't operate in the regions where it would make sense.

 

In the system of a sailboat, is the mast that critical? What's the benefit from a bone stock standard mast vs a hyper complex super specialized one? How far out in the significant figures do you have to go to perceive a tangible improvement?[/QUOTE]

com fish
Sail-mast are often compared to as engine-tran. The two should be comparable. As it does little good to put a souped up engine in front of a crap trany, or a great trany behind a bad engine.

In this case of wanting to use low performance gaff sails. There's no hope of increasing potential performance by any mast. Most gaffer choose a thicker walled or solid mast because of the extra wear and chaffing to the mast caused be the gaff and sail attachments.

 

The return on the effort, time and tooling is questionable. No aero advantage will be realized.
Don't forget to soften all machined edges and still expect added chafe potential.

 

A high performance mast on a cruising boat will give you about the same advantage a spoiler in your car gives you to go grocery shopping.

 

Probably very much easier to paint a textured or stippled layer on a plain mast, or apply an adhesive treatment, which is removable if you don't like it. Machining would be a nightmare, with flex, tool wandering and blunting, then de-burring, and who has a milling machine with 30 feet of travel that you can use cheaply ? If there was any real advantage, the America's Cup millionaires would have taken it up already, to help their ridiculous foilers.

 

Is the mast weight not arbitrary? I thought the mast weight affects the boat motion.

i.e. less mast weight, more rocking

 

A heavier mast will make the boat roll deeper and slower. The lighter mast makes the roll short and snappy. Slow rolling is more comfortable.

 

Yes, Gonzo is correct.
Whilst caught in a bad storm, captain Voss hoisted a ball of chain up the mast to increase weight aloft.
That slowed the roll, (increased the roll period).

 

It would be much simpler just to but and apply turbulator tape such as this Turbulator Tape - Materials - Covering Material & Tapes https://www.hyperflight.co.uk/products.asp?code=TURB-TAPE .I doubt it would make any more or any less difference than introducing a load of stress raising grooves.