I learned a new word today.  From she describes a storm and the cloud structure.  Do yourself a favor.  Highlight this word “Mammatus” and do a web search for images.  Amazingly beautiful.


12 thoughts on “Mammatus

  1. USC Pro-Glass is correct. I don’t know where I got the “SPC” from. I used 6″ yellow plastic spreaders like this:

    Astro 4528 Yellow 6″ Plastic Spreader, (Box of 100)

    One for each side is plenty, they tend to get a little nicked up, which leaves slight ridges. I mixed the filler on a scrap pane of heavy glass; easy to clean.

    The Pettit kit would probably work okay but I think it’s overkill if you’re going to fair with filler. The kit is designed for application over untreated metal prior to painting to etch the metal clean and then tie the metal to your primer paint. If you sandblast, your metal’s already clean. If you’ll be fairing, then all you need is a barrier coat between the filler and the metal, mostly to prevent oxidation of the exposed metal before you apply your coatings over the filler. You probably won’t apply filler over every square inch of the keel, just the areas that need built up. I’m not sure how well the filler would adhere to the Pettit tie coat. If you decide to go that route anyway, it might be worth contacting Pettit for their recommendation. I just brushed on a couple coats of unthinned epoxy, washed with Acetone, roughed up with 80 grit, then started fairing.

    Between layers of filler, I just knocked down the spots that were too high with a Stanley Surform plane like this:

    Stanley 21-296 Surform Plane, Regular Cut Blade

    If you do it before it’s totally cured, it’s like grating cheese. I sanded the final surfaces (after full curing) with 80 grit sheets on a 17″ sanding plane like this:

    A smaller sanding block is a little easier to work with in the tight areas.

    Besides using a NACA 13% template to get the cross-section right top to bottom, also use a long (5’+) straight edge to get the keel flat longitudinally and the leading and trailing edges straight. There are some excellent techniques described in Appendix B of the Final Fairing and Finishing use guide available for free download from West System:

    I’m working on the final top coats of epoxy now and my belt sander and random orbital sander work great for that.

    It’s too bad my blog series isn’t posted yet or you could see the whole process better than I’m describing here.

    Whew, that’s probably way more info than you wanted, but hey, it’s 5am and I can’t sleep 🙂

  2. Quit cloud gazing and work on your keel! ; ) I finished fairing mine this weekend – three gallons worth and I could have used more. That means I won’t have any to spare for yours, sorry. Put two layers of fiberglass on the leading edge and should be able to finish the epoxy barrier coat this week. Then it’s on to painting, finally. I’ll be glad when this project is finished, it’s gotten kinda tedious.

    • Good advice! Will post more. Somehow lost a draft progress post and now have to start over. What did you use 3 gallons of to fair with? I’m about to place my order . You must be into the painting by now.

      • I used SPC Pro-Glass fiberglass reinforced body filler for the extra strength and waterproofness. Spent last weekend at the Seattle Boat Show and watching the Seahawks give the Super Bowl away, so I didn’t get any work done on the keel. I have the leading edge taped over and the next step is to fair that in with thickened epoxy. Then two coats overall of unthickened to seal it all together, two coats of Interlux 2000e, and top it off with two coats of Interlux VC17. It’ll be bomber ; )

      • I couldn’t find “SPC” Pro-Glass fiberglass anywhere on google. I did find “USC 25050 PRO-GLASS FIBERGLASS BODY FILLER “. Is that what you used? Also, what did you use to apply it? What did you use to sand it between coats?

        I finished cleaning the keel, and found a sandblaster but haven’t been yet. I want to have the metal treatment ready to go when I do. From the forum link you sent me I found out about Pettit 6456 – underwater metal kit. What do you think about using this? Will it be enough?

  3. I was looking at pictures of clouds like this but long ago, they are fascinating aren’t they… in an awesome, spectacular way.

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