Frame finishing

[llbrand]

This is my first kayak and my first soft craft.  Started with a MessAbout 'cause my knees like large cockpits.  Love the lashings.  Building a spray booth large enough to HVLP spray the skin without changing my truck's color.  I'm worried about the oil finish on the frame in the hot garage storage.  (As if the kids and grandkids will leave it in storage!)  What problems exist in using several coats of Spar Varnish on the frame instead of oil?  Weight? Lashings?

[Hirilonde]

You could roll 3 coats on in the time it takes to build your spray booth.  I don't think you would notice the difference on fabric.  On a hard smooth surface spraying pays off, but I don't think it is worth it on fabric.

 

That being said, what will the varnish do for the frame that oil won't? 

[Bcone1381]

I don't have enough experience or time on my kayak to have an opinion about the pure Tung Oil that I used. However, I saw these excerpts on another forum and thought it gave some apparently sound advice on the topic.

POST 1

While film finishes such as varnish and epoxy work very well in many applications, SOF frames is not one of them. The reason is simple: You cannot maintain the finish once the skin is on the boat. Film finishes will wear through an/or crack over time and water will get into the wood, where it becomes trapped under the remaining finish, causing rot. Oils are breathable, so while they are not truly waterproof, any moisture that is absorbed by the wood can also get back out. I prefer tung oil (pure oil, not the bogus "tung oil finish" products from big-box stores), as I have seen mold/mildew problems with boiled linseed oil, but I do occasionally use my boats in fresh water. For 100% salt water use, you don't need any finish with solid wood, but you should protect plywood

POST 2

I recall reading somewhere about saltwater "seasoning" the frame. So if saltwater still gets into the oiled frame it'd help preserve it, correct? Not the case with freshwater? And I imagine if damp/waterlogged upon reskinning it can dry out and be reoiled...

[Hirilonde]

I agree with POST 1.   POST 2 is just plain wrong.  A wooden boat kept in salt water is some what pickled.  This is why many wooden boat owners try to keep their boat in the water as much as possible.  If it can be kept damp and still salty in the off season, this is sort of almost as good, certainly better than rinsing in fresh or letting it dry out completely.    In the case of a kayak which dries out between uses, this is not the case.  And if you rinse your boat out with fresh water, as most of us do every time we use them, then no salt is left at all.

[llbrand]

The spray booth build time is probably correct.  I tend to spray everything I can, including dyes.  Lazy, I guess.

 

Yeah, I finally got to page 18 in the posts for the oil discussion vs. varnish.  I should spend more time online and less in the shop.  Sorry for wasting your time with the stupid questions.  I'll start with the typical furniture 3:2 tung oil and make decisions later on spar varnish.  I've used compatible finishes over oil, so there's no hurry to spray.  These are fresh water boats, so storage heat drying out the oils is my only issue.  Thanks. 

 

We'll get the mandatory frog pics if it ever stops raining and dries out.

[Richard Peter]

Can you use spar varnish over tongue oil? If so, are there any thing you have to do to prepare the surface? I have a whole gallon of spar varnish and was planning on using it on my boats.

[Hirilonde]

Spar varnish is an over used word, it is almost as misused as Mahogany.   It can mean a lot of things these days.  But if the Tung oil is allowed to dry really well there should be no issue.

[Richard Peter]

Thanks for the tip Dave,

The gallon of spar varnish I have (it says spar varnish on the label) if from a time just before the ban on certain High VOC formulations a couple of years ago I've not seen it since where I live. The first SOF boat plans I saw were for a canvas boat and it called for spar varnish on the skin so I picked up the gallon on clearance. Now I can use some of it on the frame. Will it work to coat a polyester skin? I don't see why not but you guys may have had some experience with it?

And what about cedar, do you oil cedar or are the natural oils enough? Can you effectively put spar varnish on cedar?

Richard

[Geoff]

To me the most vulnerable parts of the wood frame would be the notches in the edges plywood frames that the gunwhales and chines locate in. Once stringers are lashed into these it must be impossible to really coat them with any finish type. When water gets into a joint like this there is very little air flow so most susceptible to rot...

 

Was wondering if there is any downside to finishing (rounding edges and Tung Oil/Varnish etc) the frames and stringers prior to assembly and lashing*. Would probably be easier and quicker as you don't have to reach around anything... plus you would get into the end grain on the pywood notches...

 

*Yes I realize that there would be some re-finishing to do on bow and stern as you cut stringers/chines to fit.

 

Geoff

[bobsim]

  I 'pre varnished' my frames for the Stonefly and aside from having to touch up a few spots (sharp edges needing sanding and some notches too snug) there were no problems. One thing worth mentioning is the effect varnish has on the lashings - surprising how well it penetrates and hardens the sinew (I used Jeff's product.) I was surprised. My thinking was the wax would repel the finish. 

 

  Even with pre finished frames and stringers you may want to add some finish to the lashings.