Thank you, Patrick. I was worried that it would look like I am tooting my horn, and that is not the case. 73, lh -------- Original Message -------- Subject: Re: [Utah-astronomy] Seeking suggestions for repairing RH dome Date: Tue, 6 Mar 2012 23:49:55 -0700 From: Patrick Wiggins <paw@wirelessbeehive.com> To: Larry Holmes <larry@kijoda.com> Hi Larry, Excellent thoughts. Please post them to Utah-Astronomy (or I can forward your post there if you like). patrick On 06 Mar 2012, at 23:32, Larry Holmes wrote:
On 3/5/2012 8:05 PM, Patrick Wiggins wrote:> The results of today's inspection of SPOC's Refractor House dome are not encouraging.> > Basically, water sprayed on the outside poured right through to the inside.> > Leaks everywhere and lots of them.
1. First of all, Patrick, is to decide just what you want to accomplish and how that end is to be achieved.
2. The next step is to determine the total square footage to be covered. This gives you a base to start from to estimate materials required, either by club members, or by a contractor. Any contractor worth his salt will double check the figures.
3. 90%+ of success of any job like this depends upon the degree of surface preparation. You could buy the most expensive material available, but if it is just slapped over the existing surface, it is due to fail prematurely.
4. In most cases, you are going to need a sand blast. It maybe only a "sweep blast", or the product used may call for "a white metal blast." It may need only a hand or power tool cleaning. The product used will determine the specific degree of cleaning required. One item, often overlooked, is a high pressure wash to remove not only surface contaminents, but more importantly, salt. If you just do a sand blast, any salt on the surface can just be driven into the surface profile left by the blast procedure. Then, if coated over, it leaves pockets which will eventually rust, leading to disbondment& again, early failure. There are additives to add to the wash water to aid in salt removal.
5. I might as well address a couple of theroems postulated in earlier postings: a) "You cannot bond fiberglass strips to metal" is hogwash, pure and simple, as is the notion epoxy will last just a year. The paints most used by such as KUCC, the salt plants around the Lake, water treatment plants, steel tanks for potable water (total immersion service), are epoxies. The other is the idea of depolymerization due to high summer heat. Once an epoxy cross- links, it will take temps on the order of fire to do that. Just look at UDOT's bridges--their spec calls for all surfaces not exposed to sunlight to be coated with epoxy. I know as I sold the coatings used by UDOT for some 10 years. The main downgrade to an epoxy for exterior coatings is that they are not UV restant and tend to fade in color rapidly.
6. My suggestion is to use a flexible, rubberized coating. Many could be applied by brush, roller, or spray. That would mean club members could apply if you are looking to save $$. But, if you want something on the order of a 50 year life (one posting states observatories are passe, so maybe you do not need that life, just perhaps 10 or 20 years). In that case, see #1). I totally agree with Dan. This needs to be done by a contractor.
7. You may question my bona fides. I have sold (and still do) industrial coatings for over 30 years. I have been a member of NACE (National Associan of Corrosion Engineers). SSPC (they set the standards of what constitutes a certain grade of surface preparation), PDCA. Sampe, as well as various other proffessional organizations. I still maintain a membership in WEUA, a fancy name for sewage plant operators. I am not, nor do I profess to be, an engineer. But, rust& corrosion is my business. I would be pleased to sit in on any committee, or what ever, to offer any help I can. This has been kinda wordy, but I had a lot to say, so I apologize for for the length. 73, lh