seems like when I had mine out a year or two ago I weighed it but I can't recall what the figure was. Maybe a search of the archives would turn it up...
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of dik lang Sent: Sunday, September 14, 2003 4:41 PM To: [EMAIL PROTECTED] Subject: Re: M_Boats: UHMW, HDPE, Cast Bronze The HDPE that I have used is readily machinable using standard woodworking tools such as a table saw band saw, and router. I would like to know if the newer glass center board is weighted internally, and what its weight is. >From: "Honshells" <[EMAIL PROTECTED]> >Reply-To: For and about Montgomery >Sailboats<[EMAIL PROTECTED]> >To: "For and about Montgomery >Sailboats"<[EMAIL PROTECTED]> >Subject: M_Boats: UHMW, HDPE, Cast Bronze >Date: Sun, 14 Sep 2003 13:11:06 -0400 > >I lined the insides of the cheekplates of my new kick-up rudder with >UHMW >to prevent scratches to the rudder >body varnish (my rudder's design mounts the cheekplates on the rudder BLADE >instead of body): UHMW is known >as the "poor man's Teflon". My cheek plate liners have the added benefit >of making the lifting and lowering >action of my rudder-blade VERY smooth. I am very happy with the result. > >Wouldn't any weight that you might add to HDPE be subject to the same >corrosion problems as the original cast >board? Could you round the edges of the HDPE (You can't round the edges of >a piece of UHMW, at least with a >cutting tool: Perhaps with a "melting" tool.)? > >Is cast bronze really prohibitively expensive? Especially when you >consider that it would eliminate >centerboard maintenance for good? > >----- Original Message ----- >From: <[EMAIL PROTECTED]> >To: "'For and about Montgomery Sailboats'" ><[EMAIL PROTECTED]> >Sent: Sunday, September 14, 2003 12:07 PM >Subject: Centerboard Corrosion Discussion > >High Density Polyethylene plastic. I don't have a density of that >particular plastic handy but it's probably very similar to UHMW (Ultra >High Molecular Weight) plastic which weighs 60 pounds/cu ft....too >light to stay down without some lead added to it... > >Tod > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of >Jerry Montgomery >Sent: Sunday, September 14, 2003 11:02 AM >To: For and about Montgomery Sailboats >Subject: Centerboard Corrosion Discussion > >What is HDPE? How heavy is it? > >Jerry > >----- Original Message ----- >From: "dik lang" <[EMAIL PROTECTED]> >To: <[EMAIL PROTECTED]> >Sent: Saturday, September 13, 2003 8:04 AM >Subject: Centerboard Corrosion Discussion > >I have to ask the question. Has anyone considered using HDPE for a >centerboard on the m-17? It is cheap compared to the alternatives, can >be cut with a bandsaw, no corrosion, low friction, doesn't support >maarine growth, needs no maint. Stainless bushings and stops could be >inserted as needed. My only real concern is, will it be stiff enough >laterally? If this >is a real option would the lack of weight be of concern? could add'l >ballast >be placed elswhere? Jerry? Bob? any comments? > > >From: John Fleming <[EMAIL PROTECTED]> >Reply-To: For and about Montgomery >Sailboats<[EMAIL PROTECTED]> >To: For and about Montgomery Sailboats ><[EMAIL PROTECTED]> >Subject: Centerboard Corrosion Discussion >Date: Fri, 12 Sep 2003 00:57:53 -0700 > >Jerry Montgomery wrote: > >Note that the M-17 centerboards were of cast iron- not steel, which is >much more corrosion resistant. Does Mr. Warren talk about this? Also >note that the stainless wire pennant is aftermarket; we used dacron. > >Jerry > >Hi Jerry, > >That's interesting, dacron rope. Is it stable when immersed in >seawater? How often should it be checked and or replaced? Would I just >tie a knot? > >Yes, Nigel Warren discusses cast iron, the complete discussion is >below. To summarize, he says that iron and mild steel corrode at the >same rate, but have different corrosion behavior. Cast irons with >significant amounts >of nickel, silicon, or chromium rust much more slowly than ordinary >cast iron. > >Obviously, stainless corrodes more slowly, but it has problems with >crevice corrosion, especially in areas of high flow or no flow. I'll >scan that discussion in some other time. > >Regards, > >John Fleming >M-17: "Star Cross'd" > >---- > >While wrought iron is not much used today, cast iron is still popular. >The >various grades of cast iron are produced by varying the composition >(and here carbon is important) and by varying the crystalline >structure as >seen >under a microscope. The latter is done by various furnace >procedures. Hence one sees names such as 'grey iron' and 'white >iron', so called because of the appearance of a fracture. Grey iron >is basic cast iron >and >under BS 1452 there are various grades with tensile strengths ranging >from >10 T/sq. in. (150 N/mm^2) to 27 T/sq. in. (400 N/mm^2). Then there >is nodular cast iron with greater strength (BS 2789), 'nodular' >meaning that the carbon in the iron is held in compact graphite >nodules rather than flakes as in cast grey iron. Nodular cast iron >is also called SG iron, >the >SG standing for spheroidal graphite. Other names for it are ductile >iron, nodular graphite iron, and spherultic iron. Nodular cast iron >is a steel-like metal easily machined and giving a smooth finish. It >is the >most >modern development of cast iron; previously the only reasonably >ductile cast iron available was 'malleable iron'. > >Malleable iron is a white iron which has been heat-treated to reduce >brittleness. There are three groups, whiteheart, blackheart and >pearlite (BS 309, 3 10 and 333 respectively). These terms refer to the >process by which they are made and their resulting crystal structure. > >More sophisticated irons include the nickel cast irons and the >high-alloy cast irons, both having enhanced strength and ductility. > >The corrosion rate of iron in seawater is much the same as that of mild >steel, but the form of corrosion is very different. Whereas mild steel >gradually wastes away and becomes physically smaller, iron tends to >retain >its shape and outward size but rots away from inside. Superficially >it >may >look sound, but a sharp prod can reveal massive corrosion underneath. >This >form of attack is called graphitization because a graphite residue is >all that is left. > >The ordinary cast irons have a poor resistance to shock and fracture >fairly easily; they are also readily attacked by sulphate-reducing >bacteria. > >Ductile iron is the modern equivalent of cast iron. It does not >fracture as easily but its corrosion resistance is much the same. >Nickel cast iron with 1-3% of nickel is a finer-grained iron but again >the corrosion resistance is barely enhanced. > >There are families of high-alloy cast iron: irons with large amounts of >chromium, or nickel or silicon. The austenitic nickel cast irons have >a low uniform rate of corrosion in seawater and do not suffer from >graphitization; they rust but slowly on deck. These cast irons are >often called Ni-Resist, but this name is actually a trademark. The >high-silicon cast irons (about 14% Si) also have a much enhanced >resistance to corrosion, as do the high-chromium irons (12-35% Cr). >(See Tables 8 and >9.) > >Unless a high-alloy cast iron is used, with much increased cost, the >various 'cheap and cheerful' cast irons corrode at much the same rate >as carbon and low-alloy steels. > >To Conclude > >Common mild steel and cast iron are excellent materials in many ways; >they are strong and economical - but they rust. But at least the >rusting is obvious and gradual and the metal is unlikely to fail >suddenly as can happen to stainless steel or high strength metals. Some >low-alloy steels like Cor-Ten are 'slow rusting' in a marine atmosphere >but rust much like mild steel when immersed in seawater. > >All steels should have the mill scale removed before painting. > >Hot-dip zinc galvanizing is generally far superior and more 'cost >effective' than zinc or cadmium electroplating. To get the best >galvanizing ask for the work to be done to a standard, e.g. BS 729. If >the galvanized item is to be immersed it is essential to paint it, >preferably by using a self-etch primer for the first coat. >Galvanizing gives a tough >self-healing >coating and one which is quite inexpensive. > >Electroplating is a waste of time unless a standard is specified, e.g. >BS 1706 Class A. Zinc electric plating is preferable to cadmium because >the coating thickness is greater. Nevertheless hot-dip galvanizing will >give a >much longer life and yet its cost is only very slightly more than >electroplating. > >Galvanized or plated steel makes a good base for paint which in turn >gives a long life to the paint and the metal coating providing the >paint is 'keyed' to the coat. > > > > > > >_______________________________________________ >http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats _________________________________________________________________ Get 10MB of e-mail storage! Sign up for Hotmail Extra Storage. http://join.msn.com/?PAGE=features/es _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats _______________________________________________ http://mailman.xmission.com/cgi-bin/mailman/listinfo/montgomery_boats
