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  #46  
Old 12-18-2016, 05:14 AM
BertKu BertKu is offline
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Location: South Africa Little Brak River
Quote:
Originally Posted by CDK View Post
The usual current for slow anodizing is 150 mA/dm2. That doesn't sound much, but a mast has quite a surface, especially when you want to anodize the inside also.
We made instrument panels from bare aluminum, silk screened text and striping with some kind of wax, then anodized the panels in oxalic acid, removed the wax, brushed a dye over the surface and put the panels in almost boiling water for 15 minutes.
Quite a tedious job, later we used light sensitive, adhesive aluminium sheets from 3M. Not as durable, but the process was much faster.
Yes, I had already a gut feeling that I need high currents. The surface area is 4.4 meter = 44 dm x (50mm round)= 1,5 dm = 66 dm2 x 2 (inside also) = 132 dm2 x 0.15 Ampere = about 20 Ampere. I have a 12 Volt 1 KVA transformer which should do the job. Thanks for your great help.

Now,I still need somebody to tell me whether i should, for the 4.6 meter high mast, make stringers or to leave them out. Many thanks, if somebody can enlighten me. I have difficulty in calculating the forces, a 7 m2 sail and a 4.6 meter mast with a wind force of 7 m/per second. What forces will it have on the top of the 4.6 meter mast. (preferable in kgmeter) Then I could consider to place a stringer on the mast or not. Bert

Last edited by BertKu : 12-18-2016 at 08:15 AM. Reason: forgot to mention sail
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  #47  
Old 12-22-2016, 09:35 AM
BertKu BertKu is offline
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Let me formulate my question in a simpler way. Is it correct what I have drawn on the attached drawing. Is it correct that if stringers are mounted the mast will bend less. Many thanks if somebody can confirm this.
Bert
Attached Thumbnails
Folding up keel.-scan10003.jpg  
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  #48  
Old 12-25-2016, 01:53 AM
BertKu BertKu is offline
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Quote:
Originally Posted by BertKu View Post
Let me formulate my question in a simpler way. Is it correct what I have drawn on the attached drawing. Is it correct that if stringers are mounted the mast will bend less. Many thanks if somebody can confirm this.
Bert
My apology, no wonder I could not find anything on the Internet. The name is spreaders and not stringers. In the meantime I found this on the use of spreaders and have decided to place them on the mast. If at 2/3 position it is wrong, please correct me if it should be otherwise.
Thanks IKE. Bert

"What is the purpose of spreaders.
They increase the angle between the mast and the shroud. This reduces the shroud tension and the compression force in the mast for the same sideways force when compared with a straight shroud. They also break up the length of the mast into a number of bays between points of restraint. This greatly increases the mast's resistance to buckling under compression load."
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  #49  
Old 12-26-2016, 12:45 PM
BertKu BertKu is offline
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What the hick have I done wrong. I followed the advise and instructions from the Practical Boat Owner, page 66 and that of CDK and I have a beautiful anodised product. However some parts does still make low resistance while other parts are high resistance as it should. I have no hope to anodise my mast when those small jobs are not absolute perfect. They look beautiful, but I suspect that the shop who sold me the "pure" lead weights used by fishermen may have some contamination or the article stated max 23 degrees, while our ambient temperature is already 28 degrees, it is summer here. Or maybe I did something else wrong. All what I can do is to powder coat the mast now. Has any boat builder ever used powder coated aluminium mast, spars etc in their design? Bert
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  #50  
Old 03-14-2017, 03:58 PM
BertKu BertKu is offline
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Sorry that it took a little while, but here is the not yet final welded folding up keel. I had some medical treatment. Before I am able to weld all parts permanently, I have a question on the position of the keel. I am planning to place the keel, about 10 % of waterline between mast and front of keel (drawing attached) the keel is turning around 2 points and has a spring in front (photo attached) , should I hit an object, the keel will not tear loose from the hull, but the boat will merely slow down fast (10 cm)
The keel will be pulled up by the 2 stainless steel wires and placed into position with a max 1000kg tape band. Yes, yes I will have a little drag, but it is not worrying me.

My question is >>>> Is 10% fine (45 cm) or should it be less, or more. Both which I prefer not, due to the positions of the trailer rollers on which the boat is pulled into place. Appreciate your views, Daiquiri, PAR or anybody who is more knowledgeable then me.
Attached Thumbnails
Folding up keel.-20170314_184115.jpg  Folding up keel.-folding-up-keel.jpg  Folding up keel.-scan4.jpg  

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  #51  
Old 03-16-2017, 04:15 AM
BertKu BertKu is offline
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Join Date: May 2009
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Location: South Africa Little Brak River
Hi all,

Is there really nobody who can advice me whether 45 cm (approx 10% of waterline) between mast and folding up keel is fine or badly wrong. Bert
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