Anonymous wrote:

I'm surprised nobody more knowledgable than I has come along...

I recall this has come up in discussion before.  The hole definitely weakens the mast.  

I am an amateur here. All I can do is ask questions.  It's been said that a hole definitely weakens the mast. Now, I can see that being the case if the purchaser cuts a hole in an off-the-shelf, pole.  Are poles with access holes + cover provided by the manufacturer with a sleave or other form of reinforcement to compensate for (preferably all) strength lost to the hole? Perhaps a boss around the opening? If so, why worry?

I assume, from what I can see in the photo, that all holes are, more or less, oval shaped. Keep the door and seal against water? Replace the door with something else like fiberglass? Weld it on? I would say no to that. If the mast is strong enough why mess with welding that might introduce unseen weaknesses. 

If I were looking to buy that pole, and I couldn't examine it personally, I'd call the manufacturer and ask to talk to their tech department.  If that failed, I would call on a friend who is a retired structural engineering professor. If he didn't have any answers, I'm sure he knows where to go for them.

Assuming the hole is not a problem, I would want to avoid placing it near the partners. Perhaps midway between the the deck and the boom, with the hole facing aft. If there is anything protruding, it might catch on a rope or something. That involves cutting a little off the bottom of the pole. If a cover/door is aesthetically offensive, it could be modified to look better.

Which of the poles in the eBay pictures is the one in question? I assume it is the coloured pole in the right hand picture which runs out of the photo to the right and the clean looking one in the middle of the left hand picture.

David W wrote:

If anyone is interested in purchasing one for a mast, maybe they should find out who manufactured them and ask the manufacturer if they would produce one for them without the access hole. They may even get a discount on the price, but definitely not as cheap as those on Ebay!!

We've been all around this before, David. Probably the main manufacturer in Europe is Nedal. Yes, they would probably be happy to open a trade account, if you can persuade them that you will buy sufficient tonnage of tubes to make it worth setting up the machinery for a run. For one-offs, you get directed to one of their stockholding agents. For a while, the UK agent in S Wales was ready to supply us, that's how I got Weaverbird's mast, but then they changed their minds and the supply dried up.

Anonymous wrote:They both have an access hole ~ 600mm long by ~ a third of the circumference (the black tape on the fourth image is holding the larger tube's access hole cover in place). There is an internal reinforcing sleeve, but to my mind this is way too big a hole to think of including in a mast. So in my view, both should be considered as possible topmasts for a lower section of timber or parallel aluminium tube.

I called a friend of mine who is a retired structural engineering professor and asked his opinion on using poles with access openings. I described the poles from your information and asked him this question: "Would it be correct to assume that the manufacturer of these poles would have added appropriate reinforcement, in the form of an inserted sleeve, to compensate for the loss of strength from the holes, matching the strength characteristics of a tube without any access holes?" He said that is quite possible but the best person to ask this question should be the engineer who designed them in the first place. I asked another question: "Would securing the cover by welding or rivets or whatever cause another problem, over building, to create a "hard spot" that will "attract" extra stress? He said that is quite possible. So, it's possible to just leave well enough alone and use them as is. However, I feel the cover should be secured with some kind of sealant so it doesn't leak and work loose.

You might ask, what about the boom? Will it come to bear on the cover and dislodge it? I think if you install the mast with the 1/3 mast circumference cover, that is, the 120 deg. "wedge" containing the cover, so that the centreline of the wedge is perpendicular to the centreline of the boat, the boom will not lie against the cover. On a rare occasion, it might happen by accident so some kind of safety device could be added. 

What I'm proposing seems counterintuitive. Unconvincing. Quite understandable. Why am I confident? There are millions of aluminum light and signage poles distributed throughout the world. There has been plenty of time and opportunity to develop safe and durable products. But in the end, if you want reassurance, as my friend suggests, talk to an engineer who is well informed on this subject. 

" ... who better than those of us in this Association who have a design/engineering background and who have successfully built and used unstayed masts?"

The question here is what effect do access hatches have on the strength characteristics of the aluminum poles we would like to use for our junk rigged masts. My particular question is, could we, in the case of the pole you you showed us, just work around them and leave them alone, except to seal them against water intrusion and avoid letting them come in contact with booms and mast partners?

Who better? Someone who has access to information, gathered in research facilities under controlled conditions using standardized methodology. Would their modelling come close enough to resemble our operating conditions? Good question. I would guess they are but that's one of the first questions one would ask. My guess is yes. Surely manufacturers of these things have on file, the results of tests made with their products.

Has anyone among us tried using a pole with an existing access opening?