MartinRF
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Posts posted by MartinRF
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OK, I don't have any photos of the end result but this is the second to last coat in the making. International Perfection with ~20% thinner and at some 8 C. Only the port hull was painted when this photo was shot.
The last coat was put on the day after and did not come out this good. Because it was a little warmer? Because it is harder to judge how much you apply when there is no shift in colour or gloss? Because paint flows differently on a sanded surface? Becuase I did not hit the correct viscosity as accurately?
Anyaways, it looks OK from even a modest distance -- at least while still under the tarp.
The very first and failed coat was done using Hempel's 2-pot paint. I don't blame Hempel for the failure but there are differences. Hempel's product 'dries' much quicker which makes it easier to work on the second hull but I guess that may have contributed to my failure -- unless keeping the thinned paint in a plastic bottle had saved the day even with Hempel's paint. I like the whiteness of Hempel better than International's which I would call cream- or milk-white even though International would like you to think of snow.
The reason for switching from Hempel to International was availability.
Finally, comparing the newly painted 'insides' to the partially yellow 'outsides' today I could see that my long-boarding efforts have improved things.
/Martin
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Work progresses and I may be in the positions to launch next weekend.
I do think I finally reached the level of the one boat length rule. Keeping viscosity in check by keeping the paint in a bottle and squirting paint on the foam roller as I went really helped. Some non-timely rain did not help...
And that long-term weather forecast actually came true. This weekend has been really nice weather-wise.
/Martin
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Test painting already done, sort of. The very first square metre or so painted on Saturday came out really nice. This was when I had good thinning accuracy having added a known quantity of thinner to a known ammount of paint. Then I lost track of viscosity and didn't manage to fully compensate for evaporation. Or at least, this is my theory and why I think keeping the thinned paint in a closed bottle and none of it in the roller tray may help. I did keep a lid on the container for the paint but there was always some paint in the roller tray.
Temperature between 15 and 20 degrees? I see nothing that warm in the forecast until May 22 and we all know about long-term forecasts.
/Martin (living at N59 and some)
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I am having problems wth the boat length rule. First coat of paint went on on Saturday (rain on Sunday) and I am clearly out of practice.
Sanding again -- yeah, it's that bad
I *think* my problem was I did not control the viscosity well enough but I have a plan for the next coat that I think will make me less dependent on varying evaporation rates (wind, sun...): Keep the properly thinned paint in a big PET bottle. Make small *small* hole in cap and pour paint right on the roller -- keeping nothing in the roller tray.
What do you think?
/Martin
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It just struck this short video shows my sheets.
/Martin
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Line between aft beam and boom: 5 mm Dyneema.
The other line is 10 mm polyester double braid. Smaller diameter would also work with gloves.
The blocks for the Dyneema line are Harken wire blocks.
The blocks under the boom are home made. Here is the moving one:
Much lighter than anything I could buy at the time since I engineered it for a relatively low load for 60 mm sheaves.
The block attached forward under the boom is somewhat different and based on sheaves from Fredricksen. I don't remember diameter but most likely 60 mm.
More photos:
/Martin
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OK, I will try to meet the boat length rule this time.
Last time I painted these topsides I ran out of daylight while putting on the last coat of paint...
/Martin
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The boatlength rule?
/Martin
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GregW, interesting observation regarding thinned paint and rolling it. In some resent paint projects I have noted that the first rolled coat comes out very nicely -- pretty much the same as sprayed. The second coat is never that good for some reason but I have never tried that much thinning.
Never heard of Altex. Over here we have a choice of International and Hempel plus whatever car paint shops use.
Aditional information: I am only doing the 'inside' topsides this year. I expect to do the 'outsides' next year.
/Martin
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Yes, spraying is very tempting even though I have no experience of it but as you see in my photo the space between the hulls is less than 50 cm for most of the hull length.
Any particular reason for recommending International?
/Martin
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Last spring I realized re-painting was overdue but too late... So this season instead and last fall I decided to do what never happened when we built the boats 30 years ago -- longboarding:
If all goes according to plan tomorrow will be the last day of longboarding and painting will start next weekend. What to use? My current thinking is epoxy primer followed by 2-part polyurethane top-coat. Spray painting is out of the question, I think (not enough space between the hulls).
Thoughts?
TIA
/Martin
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Our sailing season is roughly 5 months long and the rest of the year my boat sits dismantled on its trailer and under a tarp. Trampolines stuffed into the port hull and sails into the starboard hull.
/Martin
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Webbing-loops sewn to stout sail-cloth:
Poly-mesh is folded around the tramp edges before the sail-cloth is sewn onto it.
/Martin
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WRC is not very rot prone to start with.
My boat is mostly not WRC since we could not find enough of it on the Swedish market back then (30 years ago).
I have had no rot problems worth mentioning or remembering but then I have been pretty quick at patching up dents and whatever to stop water ingress and later on made proper repairs.
My main head ache has been UV radiation deteriorating things where I have opted for clear finish. Sooner or later the wood-epoxy bond gives...
Clear finish 'indoors' is a pretty good idea though since it facilitates inspection.
/Martin
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This stuff?
http://shelterritetarps.com/prodspec.html
Which weight?
How is it attached to the poly mesh?
Here is a photo showing how I used a similar material combination on my old trampolines.
The new ones are built differently. I have no good photo of the reinforcements but instead of grommets there are webbing hoops sewn to a wide piece of heavy polyester sail cloth. This is then sewn onto the poly mesh. You see the stitching in this photo:
(I have changed the lacing scheme since)
/Martin
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Hmmm, so you have roughly 1 m more waterline than I have and 50% more empty boat weight. My guess you will only see a small speed increase from changing prop -- you are limited by waterline length. At 7 knots I guess you notice transverse waves in your wake.
/Martin
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Quick assessment without being able to go there and see what it actually looks like: To me it looks like the area where the grommets are anchored is under-built.
My tramps: http://hem.bredband.net/b262106/Boat/trampolines.html
/Martin
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What design by who?
/Martin
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Very impressive.
/Martin
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Western red cedar has density of 380 kg/m3. I can't find the sheer properties at hand but I would guess high density PVC foam is superior to cedar by far.
My database on material data says 6 MPa shear strength for WRC @ 320 kg/m³.
200 kg/m³ PVC foam (Termanto) has 4.7 MPa.
Sources: data sheet for PVC, Wood handbook and/or Gougeon's book for wood.
/Martin
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This may be of interest:
http://hem.bredband.net/b262106/Boat/Sym_vs_Asym.pdf
And perhaps this:
http://hem.bredband.net/b262106/Boat/dagger.html
/Martin
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My English fails me when I try to read Silver Raven's post. What's it saying? (English is not my first language)
Tim: I would think the timber spar is up to all shear and cross-grain compression you throw at it. My rudders and my first set of dagger boards had nothing but air in them apart from the wooden spars. No buckling ever observed. My present boards have 50 kg foam apart from the redwood spar. Those boards have been with me since 1995. Uni carbon on the spar, stitched +/- 45 glass cloth wrapped around foam and spar.
Those NACA foil sections were designed for far more ideal flow than they see under a small boat sailing in waves. You are probably quite OK anyway since you stayed away from the thinner sections. I use ca. 13% for my dagger boards. The section was designed to be more forgiving to non-ideal flow situations.
offender: A thinner board in the old case should be no problem. You would have to re-shape the lower exit to avoid turbulence. This is what I did in 1995. I used home-mixed graphite-epoxy putty.
/Martin (who wouldn't mind visiting NZ some time, should improve my sailing...)
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Looks Great
I agree and I am very envious. My boat is on the hard and covered for winter -- no sailing until May next year.
/Martin
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The fibers are not the limiting factor here as far as I understand. What starts to happen at 0.3%, according to my literature, is the resin matrix starting to de-attach from fibers crossing the load path. John Shuttleworth does also mention the 0.3% limit but does not explain what happens in the same depth and only mentions onset of micro-cracking of the laminate.
Last year I did a little reverse engineering of the bow and twist limits we use for printed circuit boards (built from glass-epoxy prepreg) and it turned out those limits correlate with the 0.3% strain limit of the aerospace industry. This is perhaps a coincidence but still...
Any up-dates on this crucial aspect of yacht design are more than welcome.
/Martin
What prop pitch are you running?
in MarineTalk
Posted
Same here but I have only had one -- an Accord which is 15 years old
(Sorry couldn't resist)
/Martin