don't think that that is improving the strenght in any direction...
Currently the side walls of your beam are transfering the 1 to 1.5 tons of mast foot pressure from the underside of the beam to the top sit where the mastfoot fitting is. As you beam is rectangular this means the top and bottom planes will be pressed inwards and may develop micro cracks around the fittings.
Whith a large hole in the bottom of the beam the pin can pass straight through and transmit the laods directly to the underside of the mast foot fitting. That is one the advantage of the regular setup that you don't have anymore.
You may well be fine or you may not be with the current setup. Time will tell as I haven't done the math on your setup. Basically, keep an eye on it and if it is fine then you proven this setup to be a viable alternative.
Wouter
Here I don’t see what you mean. The mast is sitting on a threaded rod going trough the main beam (12mm hole) with a spacer between the upper and the lower walls of the beam. This rod is screwed into a nut welded on the tube going down straight to the strap. So if you want, I can by unscrewing the tube a little lift the mast foot free of the beam by tightening the strap and put no strain on the beam at all. The other edge is maybe RG, I have the feeling that he is going without a striker at all and just using the walls of a bent alu tube.
That's my experience also. No need to lose the text.
I still stress the point, fore those of you building the DS12 stick to the drawings; Scarecrows solution is the best one because he has taken all those things in consideration and I’m sure done the maths on them <img src=
alt=
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If you are using a space tube inside the mast then everything will be fine, indeed.
Wouter
Good morning everybody (or evening/afternoon depending on where you are). This whole conversation reminds me of the old saying opinions are like a$$holes etc etc.
Time to answer some questions...
1. Do you design for strength or stiffness? 90% of the structure on a boat is actually designed for stiffness, where you are considering allowable deflection and using the Young's modulas to determine what you'll actually get. Checking that a part is
strong
enough if often secondary to the stiffness requirement.
2. Why use flat bar instead of wire. Using wire is fine, however, it requires some more difficult custom parts or the use of expensive tune buckles, neither of which I thought suited this project. The system shown on the drawings is basically the same as what is featured on the paper tiger and it has worked very well for a long time and is easy to build by the home handy man assuming you can find someone to perform 1 aluminium weld. My experiance is that the cost of this weld is usually about 1 case of beer.
Gato's system is even better (although a little heavier) in terms of its ability to be built at home, however, it also requires the use of a welder. With this in mind I'd recommend people make their decision based on what welding technology they have access to. My drawings suggested people buy an off the shelf mast step, however I'll now be recommending Gato's detail.
To be perfectly honest, the other reason I went for the flat bar approach was so the boat would look as much like mum/dads as possible.
I have to make a small correction here; the system for the mast foot has been around for a while and is not of my own design, I just showed how to do it on a simple way.
For the rest I agree completely.
I’m about to start the making of the mast today, but you will have to wait for pics. Btw the hulls have been car topped for the first time and they were sitting really nice on top of my old Opel.
Some of the non-native English speaking readers may not know that saying...
Opinions are like a$$holes, everyones got one.
Larry Flynt
wikiquote
Actually the most simple setup would be how several A-cat (home)builders do it.
They make the receiver for the cone but the cone itself is nothing more then a threaded end. Basically they use a long piece of threaded rod with a tube (=pin) slid over it. They use 4 knots Two under the mainbeam; one to adjust the tension of the strap, the second to secure it. The two nuts above the mainbeam to secure the pin there. The mast foot itself it made from Stainless steel and there are several ways to make the cone receiver but drilling out the head of a large bolt like Gato has done seems to be the easiest. Both holes on top and bottom of mainbeam are now nothing more then 10 - 15 mm dependng on the threaded rod that is used.
Wouter
Piiiiiictures please <img src=
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How about your blog first Rolf. Don’t have so much more on the mast foot, but I can put up some pics on the glassing of the hulls.
Thanks Gato. Always interesting to see how others do things. 36gsm is not a lot! I heard that under 100gsm was not really worth the effort, looking forward to hear your opinions after some use. I dont think I have ever seen you use gloves when working with epoxy?? I always lay out the glass on a dry surface, and then add the epoxy on top of the glass. I tried the technique you used in the pics when I started out building stuff but the result was not very good. Mostly my own fault since I did not know about heat and outgassing of the ply, left the boat alone for too long while the epoxy set etc. Perhaps this is more suitable for the builders forum..
My blog.. Just doing the same stuff over and over as we pop out panels, but will update it tonight or tomorrow nigth as I have some new stuff to show.
Now what I really want pictures of is the A-cat striker dolphin structure Wouter describes.
Just did the sides in that 36g, to have a little resistance against abrasion and prevent the micro fissures you will get in plain epoxy coating, guess we will know soon.
Maybe we could get somebody to do a drawing using textiles (PBO) for the striker.
A PBO striker <img src=
alt=
/> What did your flat metal striker weight?
If going that route, why not use carbon fibers and lock off the ends with some epoxy?
Don’t know, but the weight problem for the DS12 if there is any will be in the other sense...
Rolf, because Gato has used 4mm ply rather than 3mm, the glass is not required as a structural element. so on his boat it is there only as a surface finisher/protector. The standard plans call for 3mm ply with a layer of more structural cloth (Two layers across the bottom).
I have 300grams in the bottom going all the ways over the chains. As I said before for those of you building STICK TO THE PLANS they are the best I have seen.
I haven't got pictures of that setup.
Sorry,
Wouter
Some small things done on the hulls. Working on the mast and hopefully there will be pics before the end of the week.
http:/
Making of the mast part one...
http:/
Opinion?
pfff. stuff
2 questions: do I see correct that both sides are different?
the track [8 figure tube], id that bought ore homebuild as well
I was puzzeld by the last 2 pictures, looks likes bulbs on the wall?
last picture shows very good results
I believe that what you are seeing is the layers added between his laminate and the vacuum bag. He used a peel ply and/or a release film. This absorbs excess resin extruded during the vacuum process along with keeping the mast from bonding to the vacuum bag.
Both sides of the mast are the same (symmetrical).
Yes Gato built the track (figure eight tube) see his notes in home building forum.
Bobcat is correct on the use of peel ply.
Note on Building a DS 12.
The carbon mast is an option only. Gato went this route due to a lack of suitable or cost effective aluminium masts in his region. The standard drawings call for an aluminium mast. Any section designed for a two crew, one on trap dinghy or small non trapese cat will have approximately the right bend charcteristics. Long term I hope to have a standard mast available, however, the cost of international shipping means that the rigs will need to be shipped in large batches to make them cost effective. So it will all come down to whether people make this F12 concept a success.
Sorry for not answering myself, I have been off line for the weekend. Well, once you have used peel ply you don’t want to live without it, saves a lot of sanding and all the “impurities” from the epoxy is coming off with it. There is no need to make this figure eight tube, you can as well take down the hale yard in the same tube as the bolt rope.
I decided to have a go for the spar as I have some very bad experiences whit single alu spars shipped from abroad, and just the transport is more expensive than the whole mast homemade. Still the big test for this one will be on the water, so before you start to build let’s wait for that one.
Has everybody died?? I'm on my way to bring the sail for the DS12, hope to be sailing before end of week.
Not dead just watching with extreme interest sorry if you feel like your talking to yourself. Your pics will make it easier to build my cats
regards