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Spar Varnish versus gasoline

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Dick Baner
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Spar Varnish versus gasoline

Post by Dick Baner » Mon Feb 13, 2006 12:53 pm

The major exterior varnished mahagony on my seas skiff is the transom. The boat spends most of its time on the trailer. On any lengthy trailer trip with the fuel tank full the sloshing of the fuel inside the tank allows some liquid gasoline to exit thru the vent tube in the transom. The fuel then runs down the transom and blisters varnish layers and also discolors the boot stripe and bronze bottom coat. Can anyone suggest a finish that will better resist the impact of fuel? (I realize that less fuel in the tank would help.) Dick Baner 1959 22' sea skiff ranger
1967 33' Chris Craft SeaStrake
"Wave Toucher III,
1965 18' Carver Captain I/O "Wave Toucher II
1974 12' Alcort Minifish,
1973 15' Chrysler Mutineer "Wind Toucher"

ed laning
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Post by ed laning » Sat Feb 18, 2006 5:43 am

Hello Dick - I wonder if it might be best to relocate the fuel vent. The present one could be left in place as a dummy, just for looks, and install a working one in an appropriate location where the varnish won't be affected. I suppose you will have a similar trouble with the paint but at least that's not so fussy as varnish. Ed

MIKEY
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GASOLINE ON VARNISHED FINISH

Post by MIKEY » Sun Feb 19, 2006 9:34 am

HI DICK,

IS IT POSSIBLE TO INSTALL A VENTED GAS CAP?

MIKEY
Last edited by MIKEY on Sun Mar 05, 2006 7:36 am, edited 1 time in total.

Dick Baner
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Gasoline versus varnish

Post by Dick Baner » Mon Feb 20, 2006 10:46 am

Perhaps my question should be 'why would not a small drilled hole in the existing gas cap do the job of venting the tank'. The cap is on the top of a standpipe at least 8 inches tall above the tank and is on the exterior of the stern deck. Too high for gas to slosh against the hole and any pressure changes would be gradual. The existing vent would be blocked off internally but remain in place. Any opinions on that approach? dick baner
1967 33' Chris Craft SeaStrake
"Wave Toucher III,
1965 18' Carver Captain I/O "Wave Toucher II
1974 12' Alcort Minifish,
1973 15' Chrysler Mutineer "Wind Toucher"

tgfinn
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Post by tgfinn » Wed Feb 22, 2006 9:51 pm

it works on lawn mowers????
tim finnerty
1960 ski boat

ed laning
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Post by ed laning » Thu Feb 23, 2006 5:35 am

I wonder why CC didn't do that when they built the boats; and no other builder that I know of. I wonder why they went to the trouble to plumb a vent hose to an outlet having fine screen over the outlet surface and this vent assembly always located on a vertical surface? Ed

Ronald Ford
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Post by Ronald Ford » Thu Feb 23, 2006 9:06 pm

If you do this I would like to know how this works, I have a '54 22ft sea skiff that does the same thing.
Thanks

Ronald Ford

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Alan Isley
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Post by Alan Isley » Fri Feb 24, 2006 8:47 am

From the archives of my '50s memory bank (not always reliable)-- I believe the Coast Guard had a requirement to vent gas tanks "overboard", hence, no vents on the deck or in the cap were allowed. This was to prevent gasolene fumes from migrating into the cockpit and bilge area looking for a spark. The wire screen in the vent was to prevent spiders and other critters from contaminating the gas tank with their dead bodies. You might avoid liquid gasolene from sloshing out by routing a longer vent hose to the highest spot under the deck, then back down to the vent fitting. This would still allow fumes to escape during normal heat expansion and evaporation of the gasolene.

Also some of the newer one- or two-part polyurethane finishes may be more resistant to gasolene than varnish is. Steve Smith is the guru on this subject.
Alan Isley
1963 28' Cavalier

George Dimion
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Fuel tank venting

Post by George Dimion » Fri Feb 24, 2006 9:23 am

Group:
On of the posts suggested plugging the vents while travelling on the highway. Please do not do this. The tank will heat, causing pressure that needs to go somewhere. The easiest path will be through the fuel pump and into the carbs. Any bumps on the road will cause the carb floats to move allowing in a little more fuel. After a few hundred miles, expect a flooded engine. That is if there is no tiny leaks in the fuel system. What used to let in a little air will now let out a lot of fuel. And that could be disasterous.
Please don't burn down any more boats.

Dick Baner
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spar varnish versus gasoline

Post by Dick Baner » Fri Feb 24, 2006 2:00 pm

Thanks for the various replies. The suggestion re the coast guard seems like a legitimate concern so I am going to try the up hose solution for now. In the meantime I had sanded that portion of the stern and applied a layer of west epoxy to see if it will resist the fuel. easy enough to sand it off if it also cannot handle the fuel exposure. dick baner
1967 33' Chris Craft SeaStrake
"Wave Toucher III,
1965 18' Carver Captain I/O "Wave Toucher II
1974 12' Alcort Minifish,
1973 15' Chrysler Mutineer "Wind Toucher"

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Don Ayers
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Post by Don Ayers » Fri Feb 24, 2006 6:02 pm

You guys are correct in your thinking.

For the historical record There was a Coast Guard reg that changed boating across the industry.

Chris Craft, as many of you know had vented their tanks through a small hole in the gas cap.

On 12-13-1940 memo Number 761 made the change from gas cap venting to overboard venting. This was effective from that point forward and all the hulls on the floor were changed, tank vents added and the use of siphen jets became standard. Now at that time the gas tank filler pipes were extended to within 2" of the bottom of the tank. This further reduced the chance of gas coming up the filler pipe. Within a month of this change came the added vents on all models to increase flow through the engine compartment. This change was on 1-6-1941. That is why you see four vents on some pre-war 1941-42 boats as opposed to two in all the photos. CC's entire production switched to what we refer to as the "clam shell" vents and go was the famous "bear claw" vents from the early 1930's.

Hope this helps fill in a little history.
Don Ayers
1959 Riva Ariston
www.RivaForum.org
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Steve Smith
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varnish adhesion

Post by Steve Smith » Tue Apr 11, 2006 7:04 am

Varnish that is put on wood primed with Clear Penetrating Epoxy Sealer(tm) [CPES] (also tm)] will of course stick better than varnish on bare wood. Gasoline and the chemical additives in the gas will attack varnish to some degree, and varnish just lying on the wood will come off more readily.

Assuming that a good-quality oil-base varnish product was used, and the wood primed with CPES, then that's the best we can get with that technology.

This coating system does several things. It protects the wood color and cellulose fibers from ultraviolet damage, looks nice [meaning high gloss], stays stuck to the wood [meaning stretches as the wood expands with changes in temperature and humidity] and offers some degree of resistance to water, fuel or whatever. Other coating systems should do the same at a minimum.

Fuel resistance will be better with different topcoat molecular structures than the plant-derived triglycerides that constitute varnish. Simply put, more tightly crosslinked structures tend to have better fuel resistance, as there is less space between finish molecules for the fuel molecules to squeeze in.

Primary-amine-cured epoxy products are fairly fuel-resistant. West System makes one of those. Its disadvantages are a lack of ultraviolet absorbers in the material, so one gets only the ultraviolet protection of the polymer system itself, not much. It also does not stretch very much before one exceeds the shear strength of wood, so with wood expansion a thin coat will crack or a thick coat delaminate. Being an epoxy product it will chalk in sunlight.

The two-component isocyanate-cured polyurethanes are among the most fuel-resistant polymers, and are capable of being formulated with both ultraviolet absorbers and antioxidants [although not all are, nor with equal amounts, equal technology or equal performance.] and can offer excellent maintenance of appearance, excellent fuel resistance and excellent flexibility and elongation to stay stuck to wood. I make one of those, and you can get more information about it at www.fiveyearclear.com.

dougz
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Re: Gas Tank Venting

Post by dougz » Sun Aug 27, 2017 5:13 am

Hello - I have a 1941 Barrel Back (71733) that was build in late November 1940, just before the changes Don mentions below. I am currently finishing a 4 year total restoration. Should I add the gas tank vent the same way Chris Craft did with this change? Or is there another way now that I can do it so I don't have to drill a hole in the side of my boat? Thanks.

Regards,
Doug

Don Ayers wrote:You guys are correct in your thinking.

For the historical record There was a Coast Guard reg that changed boating across the industry.

Chris Craft, as many of you know had vented their tanks through a small hole in the gas cap.

On 12-13-1940 memo Number 761 made the change from gas cap venting to overboard venting. This was effective from that point forward and all the hulls on the floor were changed, tank vents added and the use of siphen jets became standard. Now at that time the gas tank filler pipes were extended to within 2" of the bottom of the tank. This further reduced the chance of gas coming up the filler pipe. Within a month of this change came the added vents on all models to increase flow through the engine compartment. This change was on 1-6-1941. That is why you see four vents on some pre-war 1941-42 boats as opposed to two in all the photos. CC's entire production switched to what we refer to as the "clam shell" vents and go was the famous "bear claw" vents from the early 1930's.

Hope this helps fill in a little history.

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Brian Robinson
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Re: Spar Varnish versus gasoline

Post by Brian Robinson » Sun Aug 27, 2017 10:10 am

Doug, I wouldn't. Just make sure you have a 1/16" breather hole in your gas cap.
-Brian
1923 Hackercraft 23' Dolphin #03
1938 Gar Wood 22' Streamliner #6256 Empress
1952 Chris~Craft 19' Racing Runabout #363 Thunderstruck
Robinson Restoration, LLC (760) 468-1009

dougz
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Re: Spar Varnish versus gasoline

Post by dougz » Sun Aug 27, 2017 6:05 pm

I agree, I don't want to put a hole in the side of the boat if I don't have to. But the gas cap does not have a vent. The new tank I had made has a opening for a vent line. I was trying to think of a way to vent without the hole in the side. Thanks.

DZ

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Brian Robinson
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Re: Spar Varnish versus gasoline

Post by Brian Robinson » Sun Aug 27, 2017 7:02 pm

Drill a hole in the side of the cap (valley of one of the scallops) and problem solved. Your cap may have come from a newer boat, or was filled by a chromer over the years. Double check that it vents when screwed down by sticking a wire in it.
-Brian
1923 Hackercraft 23' Dolphin #03
1938 Gar Wood 22' Streamliner #6256 Empress
1952 Chris~Craft 19' Racing Runabout #363 Thunderstruck
Robinson Restoration, LLC (760) 468-1009

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Bilge Rat
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Re: Spar Varnish versus gasoline

Post by Bilge Rat » Mon Aug 28, 2017 6:12 am

Previous boats that I owned had the same problem. On the Lyman I currently own, I installed one of these fuel/air separator to "trap" any fuel from leaking out the breather. Granted, I had enough room on the inside of the transom to install this in the breather piping. I used the larger one. It has work very well, never had an overflow down the varnished transom.
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1966 Lyman Cruisette 25 foot "Serenity Now!"
1953 Chris Craft Sportsman 22 foot "Summerwind"

dougz
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Re: Spar Varnish versus gasoline

Post by dougz » Mon Aug 28, 2017 12:58 pm

Brian - Thank you. Now that I knew where to look I see the tiny hole on the inside...I can drill that out. Did not know what I was looking for...thanks again.

Regards,
Doug Z.

charlesquimby
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Re: Spar Varnish versus gasoline

Post by charlesquimby » Mon Aug 28, 2017 5:35 pm

It is my understanding that the fuel tank vents typically found on topsides or transoms are supposed to have the fine mesh to serve as a flame arrestor. That the screen keeps out bugs is a secondary advantage. Also, if there is enough room between the deck and the top of the tank, use marine fuel hose with a high spot in it to help prevent the fuel from finding its way out of the vent line. CQ

bflaherty
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Re: Spar Varnish versus gasoline

Post by bflaherty » Wed Aug 30, 2017 5:19 pm

I just solved this exact issue on our '69 Cavalier by cutting the horizontal section of vent tubing out and replacing it with EPA approved fuel hose that I looped up to the bottom side of the aft deck, then back down to the factory vent. I can now safely fill the gas tank to the full mark on the Chris Craft fuel stick and I don't have any fuel running out of the vent, even when backing down a steep launch ramp!

Depending on how much vertical room you have to work with you might consider using one of the new diurnal fuel vent surge protector valves in the vent line. They require about 10" of vertical line in order to work properly but they will never allow liquid fuel to escape. https://www.fisheriessupply.com/attwood ... tor-1675-6
Brian Flaherty
1969 Chris-Craft Cavalier 17 Ski Boat "TUPPERWARE"

"You'll never discover great lands, with your feet planted in the sand"

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tuobanur
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Re: Spar Varnish versus gasoline

Post by tuobanur » Thu Aug 31, 2017 10:16 am

Having the same problem on my 41 deluxe runabout which vents out the side. I only have a couple of inches above the tank to work with which gives no room for a loop. You guys have me thinking that maybe I need to blank off the vent tube and drill a hole in the cap to cure my problem.
I also learned the hard way that a stopper in the vent while traveling is not a good idea. With the way it is now I have to wait until I get to my destination before I fill the tank, a real pain in the ass.
Terry
1941 Model 101 (16') Deluxe Runabout "Miss Dot"

jim g
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Re: Spar Varnish versus gasoline

Post by jim g » Thu Aug 31, 2017 8:23 pm

Using non ethanol gas helps.

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