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MrMartyr

Kilz for SOF Frame Coating

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OK folks, here goes.

 

I am gathering materials for my 1st skin boat and I have found a local source for marine grade ply even, MDO, for the frames and high quality CVG Cypress to use for my stringers. I was really excited to learn (from the Googles, of course) that Cypress is actually a very good wood for boats due to it relative weight and its rot  resistance. But, the cavet is that this cypress is kiln dried and the supplier warns that it MUST be well sealed to prevent warping as is absorbs moisture.

 

I've searched the threads here and haven't found this specific question addressed yet......  is Kilz (water or oil based) a suitable product to coat and seal the frames ans stringers from water intrusion before skinning the boat?

 

Other than the obvious issue with it being white and covering up the natural wood tone are there any reasons to not use Kilz on the frame? 

     (SIDEBAR....Has anybody tried tinting Kilz???)

 

Are there preferences for oil or water based? Why?

 

I'm looking forward to seeing what the experience has to say.     

 

Blessings,

Marty

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MDO is not a marine plywood and structurally it is no better than any other Fir plywood for cutting out frames.  Don't let the smooth surfaces fool you into thinking it is good for this application.  It was designed for making signs.

 

I can't imagine Cypress warping when cut into strips that are lashed in numerous places to frames.  Wide boards maybe, but not stringers. If stored dry, your SOF really does not need sealing at all. It is the consensus however that a coat of oil is a good idea.  If you really want a painted frame I see no down side except the normal maintenance of painted wood. If you want a color, why not buy colored paint?  Yes, you can tint primer, and it is often done, especially when dark or bright paint will be used over it. If you do paint, nothing works better on wood that gets wet than oil based products.

"Cypress wood is very durable, stable, and water- and rot-resistant, making it suitable for building and heavy construction. Other uses where its properties make it a good choice include caskets, piers, bridges, boats, siding, sashes, doors, stadium seats, posts, cooperage and railroad ties. "
https://www.woodworkingnetwork.com/wood/hardwood-softwood-species/cypress_127745713.html

Bottom line, I would find some Baltic Birch or BS 1088 marine ply, definitely use your Cypress and just oil the frame with Tung or boiled Linseed oil.

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Marty:

Hirilonde speaks truth. All wood absorbs water, gives up water, and changes shape as a result. As it absorbs water, wood expands across the grain. Warping happens when the structure of the wood fibers in the board have some asymmetric properties. Thin cypress stringers will have little tendency to move laterally and that movement will be limited by how they are integrated into the structure of the kayak. As far as "sealing," there really isn't such a thing. You can limit the rate of water moving into and out of wood by application of a coating, but you can't stop it. Even wood fully encapsulated with epoxy resin takes up water, but at a slow rate. Bottom line is don't use Kilz because 1) it won't provide any benefit, 2) it will cost money, 3) application will cost you time, and 4) you'll have a funny-looking white frame (of course, aesthetic opinions may vary).

I'm jealous about your access to cypress. It is a wonderful wood to work with and can make a nice, light boat. Have fun!

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I agree with Dave.  I have had one stringer warp a little with all the boats I have built and it wasn't a big deal.  Cypress would be my go to wood if I could get it easily.

 

I have left the frame bare. I have used paint, varnish, poly, oil and probably some more and now I just use what ever I have or the client wants.  I think oil. poly or varnish look the best since the wood looks like wood.

 

If the 'marine' plywood you  have found is American made Douglas Fir, it probably crap. At least that has been my experience. Lots of voids in the ply's, horrible surface finish, splinters when cut. Nasty stuff and no way would I sell you a kit made from it. There maybe some good stuff made here in the US but I have not found it. That is why I use imported plywood. Baltic birch is still my favorite, best quality vs. price I can find. Imported marine plywood is fantastic stuff but very pricey.

 

Try searching Google with terms like 'plywood wood dealers' and find the suppliers for the cabinet shops use. Skip Lowes, Home Depot and the like. You want the guys out in the industrial parks outside of town. They don't have show rooms. You go the counter, tell the man what you want and they load you up. They deal with pro's so don't expect hand holding. But they are the place you will find Baltic Birch and reasonable places.

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Thanks, fellows, for the advice and guidance.

 

By far, my personal preference is to let the wood look like wood. I do not want to "paint" my frame if I don't need to. I want it to be obvious what my boat is made of, that's part of the attraction. 

But, just to make sure the base is thouroghly covered.... the opinions given concerning cypress stringers not warping, apply even to kiln dried lumber. Correct? (Sorry, my ADD brain just has to ask 😧)

 

Frankly, I am leaning toward using tung or linseed oil. Easier application and handling of the work pieces after coating, easier cleanup, cost, avialiabity..... and they would simply enhance the natural beauty of the wood.

It also seems to me that the oils would provide reasonably good protection from moisture while allowing the wood to "breath" and let the wood shed any excess moisture that it did happen to absorb.  

 

 

The supplier I found for the cypress is in Austin, TX. (Only about 1/2 hour from my house. Local pick up and no hassel that comes with shipping. Yay!)

Their focus is on the professional, custom cabinet builder so, I am hoping that translates into clear, knot free lumber.

They have various lengths of rough sawn cypress in 4/4" @ $4.58/Bf and 8/4" @ 5.18/Bf. I am hoping get my stringers from these with minimum waste and scarfing and, minimum cost. 

 

Kudzu,

In your post in FAQ regarding what ply to use for frames and what to avoid you mention MDO as good alternative to marine grade ply. Is there anything I need to be looking for to rule in (or out) a particular MDO product as suitable?  

The MDO is considerably less costly than marine (1/2" is $62/ sheet vs $105). I really don't mind the extra cost for the marine grade if that is truly superior. But, if I can get suitable MDO for approximately 1/2 the cost..... well, you know. 😊 

And, I will definatly inquire about the source and material for their marine ply.   

 

Marty

     

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All the word "marine" means in lumber grading is that the plywood will not delaminate, even when boiled under test circumstances.  It means absolutely nothing in regard to the strength or integrity of the materials.

 

The bottom line is that you want a plywood with exterior glue and 7 layers in 1/2" (12mm) plywood.  You want good layers without knots or voids.  BS 1088 marine plywood is the best there is, but very pricey.  Jeff, myself, and many others here have used Baltic Birch cabinet grade with excellent results and about half or less the price.  If the edge is 7 layers, no voids and clean, you're on the right track.

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I have never seen or used MDO. I have people talk about it and while it sounds good, I have tried a few things that sounded good but didn't work out so good in the long term. Can't recommend it at this point.

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6 hours ago, Kudzu said:

I have never seen or used MDO. 


It is A/B Fir plywood with paper surfaces laminated onto one or both sides. The paper sides are perfectly smooth and ready for primer, the core is identical to C/D ext., aka house sheathing.  If you cut it carefully, you will get a smooth both sides frame that is seriously structurally deficient.

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I Searched the inventory on the website for the supplier in Austin.

 

They describe their 1/2" marine ply as:

Grade 6566, Imported, Core Veneers (species not specified), and Aquatek-Meranti.

This would the $105/sheet stuff.

From what read that night about the BS 6566 and 1088 standards, I don't think am very impressed this stuff. Especially for the cost.

 

They do have some 1088 grade but, only in 1/4".

 

 

For some reason I had some, almost "mystical" impression in my little brain about the Baltic Birch plywood. BUT when Dave mentioned, above, that it is commonly used for cabinetry, I began to unlock myself a little. Thanks Dave!!

I was clear to me that you guys get very good results with the Baltic ply but struggled to understand how. It's cabinet plywood, intended for interior use, right?..... and you folks are using to build boats. That just don't make no sense at all.  

Then I found that that it is constructed with WATERPROOF GLUE! AH-HAH!! Now I understand, a little better, why it works so well for you guys.

And guess what.... 

My store in Austin sells a Baltic Birch cabinet plywood as described below. Sounds very familiar, doesnt it?

I called yesterday to check the price...... 1/2", 5'×5' sheet, right around $27.  

1/2"
Grade Size Origin Color Core Cut Note
BB/BB- 5x5 Russia - BB - Baltic Birch Core RC - Rotary Cut

Contains limited football patches in both sides

 

Now all I need is to go by me some ply, some cypress lumber and get to work...... after I get a few other projects around the house wrapped up that is.

 

Thanks for the guidance and the patience folks.

 

Marty

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That's the stuff.  Take a look at the edge when you get it, and again as you cut out your frames, you will see why this is the choice.  No plywood is designed to be used as we use it on these boats.  But it just so happens that a couple of them work very well, and they are all imports.

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