Mast on a Manta / Sirocco Twin

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terryg
terryg
12 posts
12 posts
22 Oct 2008 5:43am
I just finished building a new land yacht similar to the Manta and Sirocco twins.

I used a 7m sail I was given from a windsurfer. It came with the standard fiberglass mast. First time out, after about 45 minutes of abuse, the mast snapped. I easily fixed it with some conduit and was able to sail for the rest of the weekend.

There were a few Mantas out there that I was able to take a look at. I liked the three piece mast design with the inner tubes adding strength yet keeping it flexible.

I also saw some plans on this forum about building a similar style mast, but I beleive it was designed for a smaller sail.

Since my land yacht weight and sail are very similar to a Manta twin, does anyone know the tube diameter and wall thickness used on the three sizes (I believe it was three) that constructs the mast? I just want to make sure I build the mast properly.

Thanks.

cisco
cisco
QLD
12365 posts
QLD, 12365 posts
22 Oct 2008 12:52pm
terryg said...


There were a few Mantas out there that I was able to take a look at. I liked the three piece mast design with the inner tubes adding strength yet keeping it flexible.


Hi Terry, Where is "there" and where are you? I havent heard of any Mantas in Aus before. Would you like to post some pics of your home built? I am sure we are all very interested to see what you have accomplished.

Cheers Cisco

terryg
terryg
12 posts
12 posts
22 Oct 2008 12:45pm
Hi cisco,

I'm from Califronia, and I go to El Mirage dry lake bed. Kinda far from Aus! I stumbled across this forum while I was researching to build my land yacht. There was a lot of good information on here.

I have been going to El Mirage dry lake bed for about 8 years now (1 to 2 times per year), but usually to launch rockets, drive around RC cars and have a good time. Every time we went we saw these land sailers and they always looked like a blast to sail. My buddy and I built a kite buggy about 2 years ago, but never could get the hang of flying the kite well enough to have fun. We spent most of the time untangling the lines after the kite crashed.

So about a month ago I was given a windsurf sail and mast and we decided to build a land sailer. Before last month, I knew nothing about land sailers or sailing them. I did a lot of research and looked at lots of pictures before I designed and built my own.

I've posted some pictures here: webshots.com/weekly

We still haven't painted it, and need to add a small floor pan, and lower the steering 'T' a bit. Our El Mirage trip came up on us a little to fast!

There were some minor flaws such as the mast, and our support turn buckles being to small diameter to handle the force. They bent quite a bit, but we just kept bending them back. We were able to sail all three days by making repairs with what we had. And we had so much fun, we are already designing to build a class 5 style sailer.

Oh ya, and our kite buggy is up for sale!!! We are completely hooked on land sailing.

Terry

terryg
terryg
12 posts
12 posts
22 Oct 2008 1:40pm
Back to my original question about my mast.

I did not realize that Mantas were only in the US. As I mentioned, I don't know much about this stuff, but am quickly learning. I need to design the proper mast for our land sailier. I liked the design that Manta used, but I am sure there are other good designs. I saw the design shown in this forum by Paul Day, and it was similar, so I figure it was a fairly common design. Just wanted to make sure I use big enough diameter tubing and thick enough wall.

This is my plan, and maybe you guys can tell me if I am close.

Total weight: 140lbs / 64kgs
Mast height from frame: 18ft / 5486mm
7.0m sail

I have a 50.8mm x 3.175mm steel tube 910mm tall that sits on the frame. I turned down the upper 300mm so my fiberglass mast would slip over this section and rotate. I am now throwing the fiberglass mast away, since it is broken and would like to replace with a proper aluminum mast. I also do not have a problem replacing my lower mast section with a different diameter tube if necessary.

The I.D. of my lower steel tubing is 44.45mm. So my plan was to start with a 44mm x 1.47mm outer tubing and follow the basic plan from Paul Day but adding a little extra length to each section. This whole mast would slip into my lower steel tubing.

My concern is the diameter and wall thickness of the tubing. This is all I can find with sizes that fit perfect into each other. It is 6063 T832 aluminum that is used for antenna masts. The wall thickness is slightly smaller than the 1.6mm, Paul uses. But I don't know enough about aluminum to know if this little bit of difference will have a huge effect on performance.

So this is what brought up my original question, and I was hoping to find out what size the Manta tubings were since I had just seen one in person and it is similar in size and weight and uses about the same size sail. But any information that will help me build the proper mast for my sailer would be greatly appreciated.

Thanks again for a great forum!

Terry
cisco
cisco
QLD
12365 posts
QLD, 12365 posts
23 Oct 2008 4:39am
Damn fine effort there for a first time build Terry. Paul (landyacht) is probably the best one to answer your mast questions. My experience is limited to blokarts so far.

Cheers Cisco
terryg
terryg
12 posts
12 posts
23 Oct 2008 10:11am
Thanks. I'm completely hooked and can't wait to go out and sail again. I'l ask Paul if he can give me some tips.

Terry
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