Hinged mast base for Albin Vega 27

[Gene Neill]

So ... I need to devise a way to be able to raise and lower the mast on my "new" 27' Albin Vega.

The Vega's mast is located on the deck forward of the cabin trunk. So it can't be lowered aftward without smashing into the cabin top, unless a raised tabernacle like this one is used:

Or, alternatively, the mast can be lowered FORWARD, using a hinged mast base such as this one:

Because I was was so accustomed to lowering our Catalina 22's mast aftward, the idea of lowering any boat's mast FORWARD did not appeal to me at first. But I'm starting to warm up to the idea. For one thing, lowering the mast forward negates the need to have a gin pole on hand, since the boom is used for this purpose. And no mast crutch is needed when lowering forward. The Vega's cutout bow pulpit is particularly well suited to catch the mast and hold it secure.

Here is some info from Chuck and Laura Rose, demonstrating how they have lowered the mast on their Vega, using a hinged mast base and lowering the mast forward:

http://americanvega.org/images/20Lowering_and_Raising_the_Mast.pdf

More to follow ...

 

[Gene Neill]

I think I have found the hinged base I want to go with, from Ballenger Spars:

And here is some interesting info from Ballenger, on the use of their hinged bases:
Hinged Mast Bases | Ballenger Spar Systems

Now, getting around to the point of all this. Here is an excerpt from the link above:

"There are several methods of attaching the mast extrusion to the top plate. If the exising mast step casting is in good condition and with enough inherent strength to do the job, it can be attached to the top plate by machine screws, either with nuts or tapped into the step casting. The mast would be then attached to the mast step by drilling and tapping through the mast wall.

The second method is to make a plug out of thick aluminum (min. 3/4") that fits into the mast reasonably tightly. Small masts can use thick (3/4" +) Delrin or UHMW or similar plastic. The plug can then be attached to the top plate and the mast using the same method as with a casting. It is best to drill and tap all attachments since it usually works best to install the plug in the mast extrusion first and then attach it to the top plate.

With all methods of attachment , it is strongly recommended that thin plastic is installed between the mast , mast step or plug and the stainless steel top plate to inhibit galvanic corrosion. This is especially important if the boat is sailed in salt water. We can supply this material, optionally."

With regard to the first method, here is a photo of my existing mast step casting. I can see no way to attach this plate to the mast with any more than four screws at most, and not particularly snugly or strongly, either, I don't think. The plate just wasn't designed for that purpose.

So that brings me to method #2, which is to install a thick aluminum plug (unless Delrin would work better?) into the mast, and attach the hinge plate to the plug.

Is everyone confused and angry yet? What the heck is this guy's QUESTION??

More to follow.

 

[CloudDiver]

Delrin plug... Much easier to work with (band saw for shape, drum sander to refine) than aluminum, plus you wont have a dissimilar metal corrosion issue between a big aluminum plug and the stainless mast hinge. I have two plastics suppliers locally that have 'cut off' bins. Let me know what your mast section dimensions are and I might be able to get a chunk of Delrin cut-off that will work.

 

[CloudDiver]

Belay my last... you'll still need to use the original mast step because you need the tangs... So the Delrin plug will still work, just a piece of thick stock will bolt to the mast step and through to the top plate of the hinged step, the Delrin giving something to anchor side bolts/srews into.... OR, some stainless flat stock could be put through a roller to match the curve of the mast profile on the sides and TIG welded into place, then drilled and tapped for the machine screws.

 

[Gene Neill]

I was fortunate enough to find this drawing online, I think it was at the Vega Association of Great Britain's site. This is a drawing of the "plug" I would need. Sorry it's sideways:

I took the drawing to a couple local machine shops, and was given what I thought was a pretty high number, around $500 to make the aluminum plug. I know nothing of machine work, does this number sound high?

I found a 1" x 4" x 6" piece of aluminum on eBay for $21. This plug doesn't have to be absolutely perfect, could I not make one myself? How hard is it to cut 1" aluminum? Would I need a band saw? Or could I just use a bench grinder to shape it?
Would Delrin be better?

 

[CloudDiver]

Gene, hopefully uploading this drawing works..

 

[CloudDiver]

Ok, so the above drawing would be using your existing mast step with a rectangular block of Delrin to make the plug.
Yellow block - The block should be at least an inch think, 1.5 would be better and I'd even go 2 inches if I can find a hunk that thick. Its dimension should fit between the fore and aft vertical tabs and stretch across the profile of the mast section on both sides.
Green circles - This just shows that the four mounting holes may need to be relocated to match the four holes on the upper plate of the Ballenger Hinged plate. Those holes should be tapered on the bottom of that plate so flat-head machine screws come up from the bottom through the hinged top plate, mast step and Delrin plug and secure with washers/nuts, probably recess the holes with a Forstner bit in the top of the Delrin plug.
Red Curve lines - Cut the block sides to the profile of the inside of the mast. A band-saw is ideal here, but it can be done with a jig saw or even by hand with a coping saw. I'd leave a little excess material, especially if cutting by hand. Then, on a stationary disc sander, refine the curve. This ensures a square surface. The mast should slip over the plug but not have any gap or the screws/bolts that secure the mast base will squeeze and distort the extrusion.
Blue arrows - After you have a nice fit over the plug, you can drill and tap machine screw into the base of the mast to secure the mast base to the plug.

 

[CloudDiver]

You have to make sure the hinged plate you buy is big enough for your original mast step to fit on it, I can't tell the dimensions of anything from the pics. The alignment pin has to be taken into consideration along with a clearance hole in the plug to accommodate it. If your old mast step wont fit squarely on the hinged plate, we have to start from scratch and we loose the Vang tabs.
On Monday morning I have a DR appointment, that will give me the chance to hit up the plastics supply place and see if I can get a chunk of Delrin that size. I'd need to know the dimensions and if you prefer white or black Delrin, LOL.

 

[Jackdaw]

You live in FL right? How often will you be doing this? I would assume you'd be leaving the stick up for years at a stretch. If so, let a pro do it.

 

[The Garbone]

Oh heck, that first post has me worried. I had my mast step powder coated and then installed one of those stainless plates (not hinged). Now I have long term corrosion concerns.

Great thread tho, like the versatility a mast pulpit would give you.

 

[CloudDiver]

Oh heck, that first post has me worried. I had my mast step powder coated and then installed one of those stainless plates (not hinged). Now I have long term corrosion concerns.

Great thread tho, like the versatility a mast pulpit would give you.

Why? Power coating is an excellent way to prevent dissimilar metals from touching so you should have no corrosion issues. If you have a cast aluminum mast step and you mount to a stainless hinged plate or halyard plate, powder coating the mast step would be my first recommendation.

 

[Gene Neill]

Cloud, the hinged base pictured above will accommodate up to a 4" x 6.5" mast. My mast is 3 9/16" x 5 3/8". But don't go out of your way on my account! eBay seems to be pretty well stocked with Delrin scraps (although they do seem a tad scarce over 1" or so). For $20 bucks I went ahead and ordered a 4x6x1 aluminum block just to play with.

As for the corrosion, I was planning to use a thin sheet of Delrin, or G10, or something, between the mast and the stainless hinged base. In the quote above, Ballenger states: "With all methods of attachment , it is strongly recommended that thin plastic is installed between the mast , mast step or plug and the stainless steel top plate to inhibit galvanic corrosion. This is especially important if the boat is sailed in salt water. We can supply this material, optionally." I don't know what kind of "thin plastic" they use, but I'm guessing probably Delrin?

@Jackdaw: The mast will going up and down pretty often for a while. The Vega is going to be essentially trailer sailed for a couple years. Plus, I hope to use the boom as a crane to do the engine swap.

 

[centerline]

I was fortunate enough to find this drawing online, I think it was at the Vega Association of Great Britain's site. This is a drawing of the "plug" I would need. Sorry it's sideways:

I took the drawing to a couple local machine shops, and was given what I thought was a pretty high number, around $500 to make the aluminum plug. I know nothing of machine work, does this number sound high?

I found a 1" x 4" x 6" piece of aluminum on eBay for $21. This plug doesn't have to be absolutely perfect, could I not make one myself? How hard is it to cut 1" aluminum? Would I need a band saw? Or could I just use a bench grinder to shape it?
Would Delrin be better?

even thick aluminum will cut on a table saw with a carbide tooth blade, like wood only slower and with aluminum sawdust flying around.
DONT TURN THE CARBIDE TIPPED BLADE AROUND BACKWARDS, as some people seem to think you are supposed to do when cutting aluminum. this is expensive and dangerous when the unsupported teeth start breaking loose and flying off the blade....
cut with it just as you would if cutting plywood, only use better eye protection.

it can be worked down very close to the finished shape of what you need with the saw, using the sides of the saw teeth as the shaping tool, and then some sanding on a belt sander, NOT a grinder, for the final fit... aluminum will plug a grind wheel up very quickly to the point it wont grind anymore...
after the finish fit, drill the holes as needed.

delrin/acetal is also very tough, and both aluminum and delrin work/cut/sand/drill about the same way, with the exception, if delrin gets too hot it will begin to melt, AND due to the high amount of the formaldehyde content, it causes ones eyes to burn when it gets hot....
for your purpose, I wouldnt hesitate to use delrin, as it is a very strong material and will hold screws well, and yet never seize up in the block if you wish to ever remove them.

thru bolt the delrin to the tabernacle plate with countersunk screws from the bottom, and then insert it in the mast and secure it with screws or bolts.... there is never any real stress on the "plug", and with 4 or 6 #12 screws or 1/4x1" bolts holding it into the mast extrusion, its more likely the screw holes in the extrusion will tear out before the delrin gives way.... delrin can be easily drilled and tapped to hold the bolts.

 

[Gene Neill]

Thank you, Centerline! I was thinking the same thing, that there would be very little stress on the plug. I still want to make it strong, but I'm sure it will be much stronger than necessary. I actually WANT the plug/hinge base to be the weakest link in the system, rather than the cabin top.

 

[centerline]

Thank you, Centerline! I was thinking the same thing, that there would be very little stress on the plug. I still want to make it strong, but I'm sure it will be much stronger than necessary. I actually WANT the plug/hinge base to be the weakest link in the system, rather than the cabin top.

1 inch delrin is strong... it you were to fabricate 1 each of the pieces you need, one of steel, one of aluminum, and one of delrin, then drop them all at the same time in a rock crusher, when they came out the other end the delrin is the only piece that you would probably be able to use without rebuilding it..... scarred but usable, whereas the the other pieces may be unrecognizable, and absolutely so with the aluminum.
people who havent worked much with delrin, underestimate its strength.

the cabin top will take some of the stress, so the tabernacle needs to be well secured and the bolts backed up so they dont tear thru the top or work loose in the holes when raising/lowering the mast, but the hinge will be the weakest link and will take most of the stress, some of which will be transferred to the bolt/holes holding the plug into the extrusion... the deeper the plug goes in the extrusion, the more support there would be for the stress to dissipate into before tearing a hole out.... but with some care to keep the mast in alignment when raising and lowering, it will keep the stress levels to a minimum..

one could build two pieces, and stack them... when thru bolted, the plug would be 2 inches in to the extrusion, and the retaining bolts could be installed well away from the bottom edge of the mast.. the likelihood of any tearing out is minimized, and any damage will have to happen elsewhere.... but if no mistakes are made, no damage will happen

 

[LloydB]

why do the SS hinged base and the existing mast step casting need to be separated anymore than 1/16" as long as the new SS machine screws holding them together would also be separated with dielectric material.

 

[Gene Neill]

1 inch Delrin is strong... it you were to fabricate 1 each of the pieces you need, one of steel, one of aluminum, and one of Delrin, then drop them all at the same time in a rock crusher, when they came out the other end the Delrin is the only piece that you would probably be able to use without rebuilding it..... scarred but usable, whereas the the other pieces may be unrecognizable, and absolutely so with the aluminum.
People who haven't worked much with Delrin underestimate its strength.

That's really well written, Centerline, thank you again! And thanks again to @CloudDiver as well. I had been laboring under a vague impression that aluminum was the "real" material to use for the plug, until you guys set me straight.

So, Delrin it shall be!

Last night I found a 1 1/2" thick piece of Delrin on eBay to start playing with. Hopefully I can create the plug myself, with my own rudimentary "skills". I'll have to buy a band saw and a stationary disc sander, but I'd rather do that than pay someone else $80/hr to do what I could have done myself. Thank goodness for Harbor Freight ...

 

[centerline]

That's really well written, Centerline, thank you again! And thanks again to @CloudDiver as well. I had been laboring under a vague impression that aluminum was the "real" material to use for the plug, until you guys set me straight.

So, Delrin it shall be!

Last night I found a 1 1/2" thick piece of Delrin on eBay to start playing with. Hopefully I can create the plug myself, with my own rudimentary "skills". I'll have to buy a band saw and a stationary disc sander, but I'd rather do that than pay someone else $80/hr to do what I could have done myself. Thank goodness for Harbor Freight ...

anytime you have a chance to save money, AND buy a new tool, its a WIN WIN!...
just to clarify, its not that the aluminum is not the right stuff, but for the application delrin will work splendidly and without any corrosion issues ever...
the 1.5 thick delrin will cut hard on the typical band saw.... a table saw would be better.
when using band saws on delrin, what you dont want to do is allow the blade to melt the delrin, as the delrin will cool behind the blade and it will trap the blade in the material. (also when using a hole saw on thick delrin, never allow the hole saw to stop while in the cut).
thin material can usually be cut fast enough so there is no substantial heat build up
a table saw cuts much faster and the carbide tipped blade will allow a better kerf so there will be no melting of the material...
I would square it up to dimension, and then trim the corners to to proper form, until it was the oval shape you need, then finish it with a sander.... it sands about as easy as aluminum also

it may be possible to use a cutting fluid to carry the heat away and keep the delrin from melting, but I wouldnt count on it.
as I have said many times, delrin is HARD stuff.

 

[Gene Neill]

Centerline, copy that on the band saw. You posted just in time, as I was hovering over one in the store when I decided to check this thread for any more intel. I'm glad I didn't buy it. If band saws in general have a tough time with this task, CHEAP band saws would probably fail outright.

I wound up shopping all over town looking for an inexpensive but decent quality table saw and stationary disc sander. I visited Harbor Freight, Lowe's, Home Depot, Sears, and Northern Tool. Nowhere in my travels did I see a table saw in my price range that I wanted to own. But it occurred to me that a miter saw would probably accomplish the same thing, with less chance of losing a finger or two in the process. I found one on sale for a hundred bucks and couldn't say no. Stationary disc sanders were a little easier, just a matter of picking the one that looked best.

 

[CloudDiver]

Centerline is right about band-saw blades melting Delrin... well, he's 50% right. The big difference between band-saws designed cut wood and ones to cut metal is adjustable blade speed. Typically, your home shop use band-saws are 110V and have no blade speed adjustment. You can buy blades for cutting non-ferrous metals and they work ok for the most part. A metal cutting band-saw is typically more expensive because its a larger unit, uses beefier blades, has adjustable speed, and can be wired for 220V or 3 phase power. You won't find these at Home Depot or Sears... Best to look on Craigslist. With a high tooth count carbide or bi-metal blade you can slow the blade speed and cut Delrin all day without melting it.
Bad news Gene, is that compound miter saw is just as bad and high speed band saw blade... it has a high RPM that is not adjustable and will melt the Delrin if you push down hard... Possible with a fine kerf blade if you cut very gradually (light pressure on the handle) you can cut slow enough not to melt. I wouldn't return it right away though, a chop saw has 1000 uses and is a great general tool to own. With the belt sander, that's also a great tool to own for many reasons. Just work slow and gradual to make your rounded surfaces and you can avoid melting. 8 inch discs right? I have a similar unit I got from Lowes, it was about $110 and the 8 inch self-adhesive discs are stocked at both Lowes and Home Depot. Rough grits (60 to 80) won't melt the plastic as fast as medium or fine grits (120-220).