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Blanchard's formula

Discussion in 'Tips and Tricks' started by Treewater, Mar 30, 2013.

  1. Treewater

    Treewater Wooden Canoes are in the Blood

    I start a new thread because the old one became cumbersome and the only subject here is fillers not my own troubles and mistakes.

    I understand "doc" Blanchard is a real person who built boats recently in Maine. This is not intended to disparage his name.

    I converted the eight formulas on the knowledge page of filler formulas to common measurement and tried to get an idea of what is the viscosity of each
    of the small batches (not the 25 gallon OT).

    The 1964 OT formula uses 65 1/2 oz liquid for 4 lb solid = 16.4 : 1
    The Rushton formula uses 96 oz liquid for 7 lb solid (assume white lead paste is solid) = 13.7 : 1
    The Commonly Printed uses 135 oz liquid for 8 lb solid =16.9 : 1
    Blanchard's formula uses 104 oz for 5 lb solid = 20.8 : 1

    My point here is that the formulas will have varying degrees of viscosity with the Blanchard formula being the most liquid.
    Having used the Blanchard formula on two canoes as published I had not too satisfactory results. When I changed the ratio of liquid to solid to about 15 : 1 I got the rusults I had hoped to get. All of this is on #10 duck canvas. On very tight weave canvas the Blanchard formula may work different or maybe by a different application method. Any comments anyone?
    Last edited: Mar 30, 2013
  2. OP

    Treewater Wooden Canoes are in the Blood

    More on viscosity.
    The 1947 OT formula rates 18.8 :1
    The 1953 OT formula is 15 : 1
    The 1964 OT formula is 11.7 : 1 liquid to solid.

    The 1947 and '53 formulas coatained Savasol, a deadly solvent.
    the 1964 formula at 11.7 : 1 is the thickest of all the formulas and there may be an error here.
  3. Rollin Thurlow

    Rollin Thurlow member since 1980

    The solid to liquid ratio is kind of a red herring. A lot depends upon what kind of solid and what kind of liquid and then you have to consider how many layers the builder is planning on applying. There can be a large variation in the formulas and they cal still be perfectly fine.

    Herold Blanchard was a very good builder in Greenville Me. He died about 15 years ago. He worked for the Maine Fish and Wildlife and would produce 3 to 10 canoes a year. The name "Doc" was attached to him during WWII. He was not a medic but he was a very large and powerful guy. There was a famous football player from West Point military academy with the name Doc Blanchard and so the name got transfered to Herold so often it just stuck to him!
  4. OP

    Treewater Wooden Canoes are in the Blood

    Thank you Rollin. I knew when I posted the solid to liquid idea was only a place to start discussion. Obviously, the viscosity of the liquids figures into this and the chemical reactions between liquids and solids as well. Finer silica will be different than coarse silica. Etc. Etc. The attempt here is to de-mystify fillers so the average person can both mix what they need and need what they mix. The page on our website really only gave me but a few choices w/o any advice as to which I needed. (and maybe I did not know what I needed until I started). Whatever the case, viscosity and tightness of weave will determine the degree of penetration in most cases. Through my own ineptitude I had a challenging case. I had to trial and error my way through and Blanchard's formula was definitely not what I needed. I will try it again however and experiment with different ratios. Again, I wish not to disparage a good builder and certainly not a builder better than I.
    Old age dulls the memory but a well known builder in Michigan (Brian Baker?) once told me of a mixture he used based on Thompson's Water Seal, a concrete sealant. I should have wrote it down and posted it.
    I hope this all generates more discussion and additions to the Build/restore pages.
  5. Dave Wermuth

    Dave Wermuth Who hid my paddle?

    Brian is still around and has helped me quite alot. Our conversations always ended up on the subject of fillers. his canoes are very cool. Brian has used a number of fillers but the last I knew he settled on hardware/paint store latex house primer. He also mentioned basement wall primer paint, which water proofs. I was using Zinsser water tite for awhile, it was oil based. But Brian liked the latex. Zinsser had portland cement in it for the solids. The latex is cured and ready for primer in less than a week. The canvas needs an anti microbial so maybe that's what the thompson's was for? Latex primer these days is way better than the paint of yesteryear. it bonds well and oil based can go over it. I now use the latex interior/exterior primer and use a squeegee to level it. I can put on several coats in a day. thin coats, well squeegeed.
  6. OP

    Treewater Wooden Canoes are in the Blood

    Thanks Dave,
    A good fellow Brian. Enjoy visiting with him.
    Do you know his formula by chance?

  7. Steve Ambrose

    Steve Ambrose Nut in a Canoe

    Dave, how does the latex primer hold up against tripping use? I found the aircraft filler, which is water-based, not quite as durable as the traditional stuff. The oil/silica filler stands up to rocks and logs quite well.
  8. Dave Wermuth

    Dave Wermuth Who hid my paddle?

    Brian did not seem to put much worry into filler formulas. It just had to be flexible and keep water out. He uses what he can find at the hardware store. I think he preferred latex but our preferences can change over time.

    As far as durability goes, i think it's less durable than the slate-like surface of cured lead based. It does have titanium and other solids that do provide some protection. I let my canoe rock up against the granite in Canada for a short time, (maybe half an hour?) and it wore through to the filler but it can't be seen now that I've put some paint over it. It depends on how rough you are on your canoe. I think it's pretty durable with minimal care and any canoe can suffer at the hands of a careless user. I doubt many of us here are that neglectful. I think the paint and primer can handle most of the abuse I force on it. If i had to make a guess as to the difference between lead/silica/latex, I'd say silica and latex are the same and lead is better. But Don't make me swear to it. Any other guesses out there?

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