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Thread: John Henry... Easy scarfing and glueup

  1. #36
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    Default Re: John Henry... Easy scarfing and glueup

    Has anyone considered cutting on the 45 degree axis? Bias cutting...

    No seriously...I'm sure in plywood aircraft construction they use alot of plywood cut on 45 degrees. A different application I know but, and might wasteful or alot of scarfing would be needed for boat planks but interesting none the less. Anyone know much about this?
    What would be the point ... or advantage of diagonal orientation?

    R

  2. #37
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    Default Re: John Henry... Easy scarfing and glueup

    When I was looking into getting high quality plywood, I googled aircraft plywood and found alot of references to cutting the aircraft part from plywood so the outer veneers are at 45 degrees to the long axis of the part (but still at 90 degrees to each other). It comes up alot in build manuals for small aircraft. Aircraft build standards are pretty strict and scientific so they must have a reason 1) They think its stronger/ stiffer this way overall and 2) When using thin plywood for wing coverage it gives a smoother panel surface: I can understand this as we use bias cut (biaxial) reinforcement fabrics when we have to reinforce boat hulls around round sharply curved objects. Its probabably not really practical in boats as I wouldn't fancy scarfing panels cut at 45 degrees accross 4x8 sheets but it could have applications for high performance canoes and kayaks where less material is required.

    Here's a reference from Australian small aircraft building specs:

    http://www.auf.asn.au/scratchbuilder/plywood.html

    "The stiffness of plywood can be increased without an increase in weight by laying the two outer plies so that their grain direction is at 45 to the long axis of the sheet. Forty-five degree plywood is slightly stronger than the normal 90 sheets but it is much more expensive and difficult to acquire. Humidity effects may be less apparent in the 45 plywood."

    Wing shapes and boat panels reinforced with ribs are not so dissimilar...and the inner layers of cold molded veneer/ plywood boats are layered up with strips running 45 degrees roughly to the boats axis...

    The question is: Is having all the plies taking half the load giving a stiffer panel than half the plies taking all the load?...


    Anyone built an aircraft or know more about this...?Engineers?
    Last edited by keyhavenpotterer; 03-05-2010 at 07:13 AM.

  3. #38
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    Default Re: John Henry... Easy scarfing and glueup

    Quote Originally Posted by keyhavenpotterer View Post
    When I was looking into getting high quality plywood, I googled aircraft plywood and found alot of references to cutting the aircraft part from plywood so the outer veneers are at 45 degrees to the long axis of the part (but still at 90 degrees to each other). It comes up alot in build manuals for small aircraft. Aircraft build standards are pretty strict and scientific so they must have a reason 1) They think its stronger/ stiffer this way overall and 2) When using thin plywood for wing coverage it gives a smoother panel surface: I can understand this as we use bias cut (biaxial) reinforcement fabrics when we have to reinforce boat hulls around round sharply curved objects. Its probabably not really practical in boats as I wouldn't fancy scarfing panels cut at 45 degrees accross 4x8 sheets but it could have applications for high performance canoes and kayaks where less material is required.

    Here's a reference from Australian small aircraft building specs:

    http://www.auf.asn.au/scratchbuilder/plywood.html

    "The stiffness of plywood can be increased without an increase in weight by laying the two outer plies so that their grain direction is at 45 to the long axis of the sheet. Forty-five degree plywood is slightly stronger than the normal 90 sheets but it is much more expensive and difficult to acquire. Humidity effects may be less apparent in the 45 plywood."

    Wing shapes and boat panels reinforced with ribs are not so dissimilar...and the inner layers of cold molded veneer/ plywood boats are layered up with strips running 45 degrees roughly to the boats axis...

    The question is: Is having all the plies taking half the load giving a stiffer panel than half the plies taking all the load?...


    Anyone built an aircraft or know more about this...?Engineers?
    You might try: www.eaa.org

    Look in the "homebuilders" section under "tips and tricks" they have a lot of online videos under different sections. I haven't studied the "wood construction" videos since I am interested in alum sheet metal construction, but they are a wealth of info.

    You might also try: www.aircraftspruce.com That is where I purchased the okume and spruce for my Spindrift 9N build.

  4. #39
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    Default Re: John Henry... Glassing panels

    Heres the bottom panels with screw holes filled and ready for sanding...



    Here is the setup we used to put pre-bend into the bottom panels that mimicks, to some degree, the position/shape the panel will have when the hull is assembled. Note the screw eye/string and 25# lead shot bag used to pull the inner edge of the panel down twisting the panel as it will be in hull assembly. Standard blocking supports the other side of the hull to achieve this.

    This panel is quite stiff and is denser Merranti rather than Okoume... so any pre-bend we can instill into the panel during glassing will make for easier hull assembly (less resistance to being pushed/pulled into shape) and results in less stresses in the hull after bonding. Its a simple thing to do and per our designer, its worth the extra effort in this overall fairly lightly constructed hull. If these panels had been glassed flat, the fiberglass would have added to the resistance of the panel to go into shape.



    Another angle showing the panel twist before glassing in the other bottom panel... This panel is the port bottom panel, and when the stern is level as the hull is in the water... the foot of the stem will be the lowest part of the hull, and this panel will have to twist quite a bit to get the right shape.



    The starboard panel in the same position... glass wetted out...



    This view somewhat shows the final shape of the panel with hull assembly...



    One side glassed... (hull interior surface) the hull exterior surface is next... we will maintain this bend in the panel, more or less, while glassing the bottom exterior surface ...



    Side panels next... quite a bit more bend in them... so more pre-bend will be forced on the panels before glassing. See model in post 31 in this thread...

    RodB
    Last edited by RodB; 03-07-2010 at 04:00 AM.

  5. #40
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    Default Re: John Henry... Easy scarfing and glueup

    Is pre bending a requirement of the designer, or something you guys are doing just to make life easier? The bends on those hull panels don't seem that extreme to require such measures.

    BTW ... that is probably the nicest shop I've have seen on this forum in a long time. You must be either single or married to the nicest woman in town.

  6. #41
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    Default Re: John Henry... Easy scarfing and glueup

    After putting a model together with 5/32 Birch ply... and seeing the torque required to twist the ends of the bottom panels to get the shape... we asked the designer about pre-bend advantages... and he agreed that it could help... and said that any bend you put into the panels by the glassing position of the panel just puts you that much ahead of the curve when trying to "twist" the panels during assembly. Note: if you glass panels flat, then bend them significantly, you will notice the white fractures on the inner surface from the compression.

    The model doesn't show the amount of crosswise bend/twist that will take place with the forward 3 feet of these bottom panels and the setup shown did not complicate the standard glassing process except for a few minutes setup. We actually had to wire the bottom panels forward to the cradle to achieve the "V" stem foot.

    Heres a photo of the side panels in a "test" pre-bend setup.... We will glass these like this...



    The builder is single... and a maniac flyrod Tarpon fisherman.

    RodB
    Last edited by RodB; 03-08-2010 at 04:17 PM.

  7. #42
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    Default Re: John Henry... Easy scarfing and glueup

    In glassing panels its much easier with good access to both the edges to achieve a smooth uniform job... especially with the squeege in wetting out and the second squeege coat to fill the weave.... so each panel is on its own separate stand.

    Side panel draped with fiberglass... again with the pre-bend to diminish panel stress in assembly.



    Panels wetted out...





    And the other side with the same pre-bend...



    And glassed... Boy those 25# shot bags come in handy.



    Another coat.... rolled and tipped...



    More to come... later...

    RodB
    Last edited by RodB; 03-16-2010 at 01:19 AM.

  8. #43
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    Default Re: John Henry... Easy scarfing and glueup

    Photo below: Roll and tip platten (usually 12 inches square)... with 1/2 of a 7" System III roller (cut in half with a hack saw), a 3" foam brush, and a squeege. ... One of the tool setups used to achieve very uniform consistent coats of epoxy by rolling and tipping. I prefer the System III roller pads because the center core never gets soft like many of the other brands I have used (especially with thinned paints).

    Usual procedure (coat one [pour on epoxy... standard squeege wet out], coat two, quickest coat- least epoxy used, pour epoxy on...squeegeed lightly with squeege at a 45 degree angle... to fill the weave... use diagonal strokes off of the edges wiping the squeege edge on the edge of a plastic cup to keep a clean squeege edge .... coat 3 and 4... rolled and tipped.... mixing about 2-3 oz of epoxy at a time, dumping it on the platen platform... and rolling about 10 square inches at a time and tipping with a foam brush... keeping a "wet line" like with paint. Always tipping from the new wet towards the just applied section. Note the squeege on the platten is used to clean off the epoxy completely from the platten surface before the next batch is mixed. You can squeege the last 1/2 ounce that is cooler and thicker into a cup and mix more fresh epoxy in the same cup.

    Tips here.. Optimal situation: you will get a nice glassy finish if you keep the epoxy at about 82-85 degrees when rolling and tipping (Water bath in a sink, etc when the shop is cool... not necessary in our warm temps after May). I always prefer glassing in 80 degrees plus because its so damn easy to get a very smooth glassy finish, which means a nice flat surface which requires less sanding.

    Epoxy at thinner viscosities (temp controls this) will roll and tip ... and settle to a very slick finish. If you find the epoxy is a bit too thick (cooling), use your heat gun to warm it up...once you have tipped it... and watch it settle to a very nice smooth finish. Just keep the heat gun about 10-15 inches away from the epoxy so you get a nice wide not too hot blast of air.

    Certainly, many builders pour measured epoxy out over a larger area (As in the Gougeon Book) and spread it out with a notched squeege... then roll it uniform as soon as possible and then hit it with a heat gun to help it lay down ... (flow coating) [applying all the epoxy you want on the panel in one fell swoop after initial wetout].

    Alternatively, like many non-professionals do... just pour on some unmeasured epoxy and roll it out even and then tip all. The. first ... "flow coat" method works great and just requires deriving the numbers of the exact volume of epoxy required to coat your panel... and then applying it with pre-planning to spread it out evenly fairly quickly and then leveling it with a roller... followed by some heat to level all very nice.

    The second method is really a quick guess as to how much epoxy to use and most likely uses more epoxy than needed.

    The platten method offers simpllicity and lots of control, especially for one person... mixing small batches as you move along with very little waste.

    This post edited today for broader contents.... 3/17/2010

    Next comes strongback assembly, cradles erected, and hull stitching...



    Note: the black finish of the platen is from applying graphite in epoxy to a hull bottom in the past.


    I forgot the following pic... its a shot of our package deal of starting materials ... 15 gallons of epoxy/hardener for $895 from System III. Of course, everything except the epoxy was extra.





    RodB
    Last edited by RodB; 03-18-2014 at 06:42 PM.

  9. #44
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    Default Re: John Henry... Easy scarfing and glueup

    nice update, I love the platen idea, never ever would have thought of that. I have always been the mix/pour/squeegee kinda guy.

    thanks.

  10. #45
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    Default Re: John Henry... Easy scarfing and glueup

    I can't take the credit for the platen idea of epoxy application... its by courtesy of Tracy Obrien... www.tracyobrien.com Tracy uses this procedure to achieve very level, uniform, and consistent epoxy applications when a very simple method is needed. The simplicity of just mixing small batches and moving along the panel is very effective and allows good control and hardly any waste.

    RodB
    Last edited by RodB; 03-17-2010 at 07:39 PM.

  11. #46
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    Default Re: John Henry... Easy scarfing and glueup

    Here we start the strongback setup with station cradles (female). The strongback has been sized to allow for a good working height for the hull and to provide easy access. This setup is quite simple and very little bracing is needed as the station cradles and the side panels add so much support and stability for assembly.



    Station 24 cradle mounted....



    Station 24 and 72 cradle sections...



    Station 120 cradle added...



    And here, all cradle stations in place...



    Each station secures the panels in the proper position insuring proper hull shape. The panels will be wired to some of the cradles for bonding.

    So, now the side panels will be placed in the cradles... with the bottoms last... more to come soon...



    RodB
    Last edited by RodB; 03-18-2010 at 04:53 PM.

  12. #47
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    Default Re: John Henry... Easy scarfing and glueup

    A few more detail photos... Level string alignment for the station cradles.





    Station cradle attachment... very simple.



    This end on shot kinda shows the hull shape to come. Note the 1/2" clearance cutouts on the cradles, which allows for the ply panels to "cup" some without restraint. This was the first project I had a chance to really put my new barrel grip Makita Jigsaw through its paces. With the LED light and air jet keeping the blade free of sawdust, I think Makita has one of the best three out there... Festool, Makita, and Bosch.





    Panel stitchup next...

    RodB
    Last edited by RodB; 03-18-2010 at 04:41 PM.

  13. #48
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    Default Re: John Henry... Easy scarfing and glueup

    Heres a few more pics of the rough model we have built... giving somewhat of an idea of how the hull will look in shape. Neither Mark nor I want to take the time to finish the model. This design is pretty much a compilation of all the best features of the top flats boats in production today... and is the results of lots of work (research) and of course designer fees to get here.





    And a profile, which is not showing very well because the degree of finish of the model is not very far along. With final shaping, sanding and painting the shape would be much easier visualized.





    Contiinued with panel sewup next.

    RodB
    Last edited by RodB; 03-18-2010 at 04:55 PM.

  14. #49
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    Default Re: John Henry... Easy scarfing and glueup

    Really interesting.
    I can't help but laugh every time I see a view of the "shop."
    My wife seldom forgets to remind me of the motorcycle she found in my living room when we met
    Why do women get so exercised about things like that?

  15. #50
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    Default Re: John Henry... Easy scarfing and glueup

    It was the only way Mark could get started on the boat before May...and he plans to be fishing in Florida for Tarpon in mid-May...

    I guess its not a bad thing to be single sometimes....

    She'll be outside in a few weeks.

    R
    Last edited by RodB; 03-18-2010 at 05:03 PM.

  16. #51
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    Default Re: John Henry... Easy scarfing and glueup

    I like seeing that reverse chine too, is that about 3" wide with about a 1" drop?

  17. #52
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    Default Re: John Henry... Easy scarfing and glueup

    thats about right... like the Dolphin skiffs or the Mavericks etc,

    R

  18. #53
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    Default Re: John Henry... Easy scarfing and glueup

    One of the final steps on the side panels before stitching up in the cradles... routing a 1/4" round radius on the inner stem edges so that they mate together very smoothly when stitched together. Note the sanding board is used to finish the edge for a nice smooth uniform radiused edge.



    Heres the port side panel in place on the cradles.



    Both side panels laid in place... ready to be wired to the cradles.



    Here both side panels are measured precisely for positioning in the cradles... 24" past the line at the base of the strongback. Note: the strongback was fabricated to be only the length that allowed the cradles to be setup... no longer.



    And here you can see the port side panel wired to the sternmost cradle ... station 24 along with some others.



    An exterior view of the panel wired to the cradle... standard old iron tie wire twisted tight.



    Con't

    Rodb
    Last edited by RodB; 03-20-2010 at 04:33 AM.

  19. #54
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    Default Re: John Henry... Easy scarfing and glueup

    Heres the hard part... after securing the side panels to all the cradle stations... the stem section of the side panel needs to be stitched together... which will take some serious torque. Glassing the panels with "pre-bend" in them hopefully will help here. Usually the stem ends are stitched together before laying the side panels in the cradle... we are just trying it with securing the panels at all stations very firmly... then pull the stem together.



    Here you can see the top of the stem seems to be going together fine...but the bottom is really requiring a lot of twisting side to side on the panel... and also the side panels where they are wired to the foremost cradle are pulling out some ... away from their proper spot.



    Its late... quitting for the evening... more tomorrow.

    R
    Last edited by RodB; 03-20-2010 at 04:19 AM.

  20. #55
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    Default Re: John Henry... Easy scarfing and glueup

    Great thread. Learning a lot here. Thanks for continuing to show us your build.
    Murphy

  21. #56
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    Default Re: John Henry... Easy scarfing and glueup

    Continuing with the stem stitch up... here I doubled the wire at the bottom of the stem for additional strength in addition to adding a flexable 3/16" threaded rod to help close the gap.



    The force needed to get the panels in place can easily pull the panel bottoms away from optimal position at the foremost cradle. Here I was trying to get the bottom of the side panels in the proper cradle position "exactly" with a 2x4 wedge and a large "C" clamp. Its important to note that in a design like this, where flat panel construction is pushed to the limit... extreme accuracy is necessary in the cradle setup, panel fabrication, and panel positioning before bonding.



    This pic shows the bottom edge of the side panel... at the final station before the stem. Note the positioning of the actual bottom edge of the panel is the important thing here... with trimming part of the two inch vertical positioning strip (The white line shows what part was trimmed off) allows the panel to "cup" (which is ok and expected) but still be in the exact right place for proper hull geometry. The corner at the bottom is exactly where the panel edge needs to sit for all the geometry to work out.



    Here, the side panels are in proper position on the cradle... note, the secured blocks of wood used along with deck screws and washers to pull the side panels into proper position without damage to the panel surface.... This shot really comes later as you can see the bottom panels laying in place...but this is a good shot to show proper positioning of the side panels in the foremost cradle.





    Heres a good view of the final sew up with wire... before bonding...



    Con't

    R
    Last edited by RodB; 03-20-2010 at 04:28 AM.

  22. #57
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    Default Re: John Henry... Easy scarfing and glueup

    The following diagram illustrates the method shown above for pulling panels into position. Note, the screw shown could be replaced with a bolt and nut if more torque was needed. The main thing to realize in situations as this is to just use anything that works... twisted wire via vice grips, screws and blocks of wood, nuts and bolts and blocks of wood, etc. etc. The bottom of the panel is precisely where it is supposed to be.



    The bonded stem... "overhead view".... lots of thickened epoxy ... biax added atop pdq.



    Next, the bottom panels will be laid in... here they are stitched together just prior to laying out in the hull. Always do the stitching like this before putting the panels in position because its just so much easier with the panels laying on sawhorses.



    The bottom panels lay out inside the side panels with an overlap the entire length of the hull on both sides. This overlap will form a "reverse chine" the length of the hull.



    This shows the panels in place...but not really.... some serious fitting to go at the foot of the stem. Here, the panels are wired in place the back 2/3 of the hull, the front foot of the stem is the next task...



    Kinda looking like a boat now...



    Con't

    RodB
    Last edited by RodB; 06-01-2012 at 12:01 PM.

  23. #58
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    Default Re: John Henry... Easy scarfing and glueup

    One more pic...



    The transom is in order next but the bottom panels need to be seated properly first. The side panels are 9mm Okoume, but the bottom panels are 9mm Merranti... so they are stiffer and will take some effort to get them into position for bonding.

    Later,

    RodB
    Last edited by RodB; 03-20-2010 at 04:15 AM.

  24. #59
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    Default Re: John Henry... Easy scarfing and glueup

    The bottom panel fitting comes next... and we had to use some strong leverage to get the panel in shape. Plain old 1/2" threaded rod with a fitted block of wood that matched the cradle bottom...

    As before, anything that works is allowed in a situation like this.
    Heres a pic of the hull interior with the bottom panel in reasonable shape.



    And another... NOTE: THE BOTTOM EDGE OF THE BOTTOM PANELS IS RADIUSED WITH A 1/4" ROUND OVER ROUTER BIT SO THAT YOU GET A NICE FIT OF THE BOTTOM PANEL EDGE AGAINST THE SIDE PANELS. ADDITIONALLY, THE TOP CORNER OF THE BOTTOM PANELS ALONG THE CENTER LINE ARE SIMILARLY RADIUSED SO THAT AS THEY COME TOGETHER YOU GET A NICE TIGHT FIT WITH NO GAPS.



    Heres a pic of the anchor underneath the hull...two 2x6's attached to each side of the strongback.



    A closer view...



    Wiring/stitching in the bottom panels continues next along with transom fabrication soon following.

    Cont'''

    RodB
    Last edited by RodB; 03-22-2010 at 04:32 PM.

  25. #60
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    Default Re: John Henry... Easy scarfing and glueup

    Well, now its plain how using the house as a shop for a couple of months makes sense... we had over 5 inches of snow Saturday, even tho it was 75 degrees on Friday. Mark will almost have the boat done by real summer weather...



    Continuing, the entire hull bottom was stitched (twist wired) with iron tie wire that has been coated with Johnson's paste was (as a release agent). . A pair of vice grips are used to twist the wires tight, just remember to always pull hard as you twist so as to tighten the wire and not just twist it to breaking. A little practice with this and it becomes second nature.

    Here, Mark is just sticking in wires from the top, to be twisted tight from underneath.





    Just about all tightened up...





    Ready for bonding....

    Cinched up tight... nice tight fit.



    Con't.

    RodB

  26. #61
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    Default Re: John Henry... Easy scarfing and glueup

    The wires seem too many, but its the only way to keep everything buttoned up solid until bonding is completed with epoxy. The numerous wires just hold her together very tight, perfect for filleting... additionally, ,when your crawling around inside, the wire ties are very strong.

    Usually on Stitch and glue construction, the transom is installed before bonding, but with this variation... the stern cradle holds everything so well in place that the measurements of the transom are precisely the measurements of the stern transom area... so we decided to fabricate the transom in warmer weather and just do the initial bonding today.





    Bonding begins (filleting) with my favorite filleting tool... which is sanded down after each job. Filleting mixture, standard System III epoxy thickened with equal amounts of cabosil and wood flour to a "peanut butter" consistency.







    The center keel panel will be completed next, with intermittent fillets and then removal of the wires... then the filleting will be completed, although not as thick as would be required to cover up the tie wires. Biaxial will come next... and be applied to all the interior seams.

    Continued later in the week.

    Rodb
    Last edited by RodB; 03-22-2010 at 12:52 AM.

  27. #62
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    Default Re: John Henry... Easy scarfing and glueup

    Very interesting Rod, lots of stitches... I use the same wire, last good deal in boat building material.
    I normally spend a pretty good amount of time squaring up the hull before filleting. Is this not a concern with this method? Usually having the transom stitched on makes squaring much easier.

  28. #63
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    Default Re: John Henry... Easy scarfing and glueup

    Very interesting Rod, lots of stitches... I use the same wire, last good deal in boat building material.
    I normally spend a pretty good amount of time squaring up the hull before filleting. Is this not a concern with this method? Usually having the transom stitched on makes squaring much easier.


    The cradles are rock solid and we spent plenty of time and effort to be sure the setup was very accurate. The measurements we took at the transom location were perfect...both sheer to sheer and chine to chine. We could tell from the model we built that the panels would go together fine if they were accurately cutout, so we made sure of accuracy all through the process. The dimensions of the transom from the developed plans are exactly the size we have measured at the back of the hull. The Transom fabrication is next and will be a bit complicted...as we plan to have recessed trim tabs with both the plates and the power units recessed into the surfaces they are located on.

    RodB
    Last edited by RodB; 06-01-2012 at 12:07 PM.

  29. #64
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    Default Re: John Henry... Easy scarfing and glueup

    Rod, I often read/see guys "tabbing" the fillet so they can go back and remove wires and then do the final fillet once all the wires are out. I will be interested to see your method for removing the wires, or do you plan on just cutting and leaving?

  30. #65
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    Default Re: John Henry... Easy scarfing and glueup

    I'll take a guess at heat and pull. Copper wires are good for that as they transfer heat well.

  31. #66
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    Default Re: John Henry... Easy scarfing and glueup

    Rod, I often read/see guys "tabbing" the fillet so they can go back and remove wires and then do the final fillet once all the wires are out. I will be interested to see your method for removing the wires, or do you plan on just cutting and leaving?

    I learned the standard way of filleting by covering the wires and then pulling the wires after cure... but it this case, along the keel at the centerline, the area where the keel splits in two... is really a "flat" that gently levels out and widens as it gets to the final 2-3 feet and the transom where it is a 8" wide flat. The interior angle all along this keel is so shallow that I thought it made more sense to tab in areas and then pull the wire... then finishing the fillet with the end results an overall thinner fillet. Covering the fillets with a biaxial "Y" applied to the bottom center hull and the split at the back 1/3 of the hull will be plenty strong.

    I try to put a very good coat of paste wax on wire before using it to tie up a joint... so that it comes out without much trouble. I always let the wax dry so that I don't have to worry about any of it getting on my joint area and contaminating any gluing surfaces.
    I also use a solder gun to heat a wire if it is too difficult to pull out but usually with my trusty old vice grips used with max leverage like a hammer pulling out a nail, the wires pull out without any problems. Sure, once in awhile a wire breaks right close to the wood, so you need to leave the other end alone... as its your last resort to get it out with heat... cause if it breaks, I guess you have to leave a piece of wire in the joint. That reminds me, if you do happen to break off an wire at both holes... be sure to use a nail punch to drive it deeper into the wood and then fill the hole with epoxy. If you leave a piece of wire too close to the surface, later on over time you will notice spots where it is due to heat and cold cycles and condensation on the surface at that spot.


    RodB
    Last edited by RodB; 03-22-2010 at 04:18 PM.

  32. #67
    Join Date
    Apr 2003
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    Default Re: John Henry... Easy scarfing and glueup

    Mike...

    I rechecked the levelness of our setup sheer to sheer at all the cradle stations. We used an 8 foot straight edge of aluminum that we had made from a metalshop friend with a laser cutting machine.

    We pretty much had "dead on" level at all four cradle stations.



    I'll take a guess at heat and pull. Copper wires are good for that as they transfer heat well.
    Steve... isn't the iron tie wire stronger than copper? I never have tried copper.



    I also thought the rounded corners of ply panels that allow for nice tight joints in this design and in stitch and glue designs in general... might be of interest to some of the less experienced members... ie., forming a simple radius on bearing corners...

    This diagram is specific to the design we are building... although not to scale, it shows the basic details of the hull bottom remembering all the hull panels are already glassed when the hull is assembled and bonded. Note the small milled glass/epoxy filled rabbit on the bottom outside edge of the side panels, that makes for completely protected end grain with a solid epoxy/milled glass barrier. This rabbit (created with a simple bearing rabbit router bit) filled with solid glass and epoxy is a great way to achieve very tough chine edges with the end grain of the ply panels completely protected. Tape can be used to form a dam along the edge of the panel once the rabbit is cut... then just fill the rabbit with the epoxy/milled glass mixture. Finally, sand to shape.

    The reverse chines illustrated by the walnut wedges are not to scale or proportion at all...just for illustration only... The actual reverse chines will be about 2.5" in width at their widest, and tapering towards the bow.



    RodB
    Last edited by RodB; 03-23-2010 at 12:58 AM.

  33. #68
    Join Date
    Jan 2000
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    Egg Harbor Twp, NJ
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    Default Re: John Henry... Easy scarfing and glueup

    I like the epoxy filled rabbit detail, great idea...

    I waiting for you guys to get to the stage where you wrestle that hull through the glass doors in the dining room shop.

  34. #69
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    Default Re: John Henry... Easy scarfing and glueup

    I waiting for you guys to get to the stage where you wrestle that hull through the glass doors in the dining room shop.
    Four guys with two nylon straps with wrist loop on the ends... we'll carry it right out...

    R

  35. #70
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    Default Re: John Henry... Bonding and taping joints... and bulkhead patterns

    After filleting the joints, taping the joints with biaxial was next. I didn't take any pics of the process, as I thought it quite well covered in many sources... and sometimes, you just don't want to stop and grab a camera.

    Note... standard procedure for me with biaxial taping of joints is to cut proper lengths... then... apply a fresh coat of un-thickened epoxy to the smooth fillet over the joint where the biaxial tape will be applied. Leave it wet...

    Next, wet out the biaxial tape with epoxy by laying it on a work board... (I use a 15" by 25" board) ...and then pouring epoxy on it... use a roller to evenly wet out the tape applying one ounce of epoxy to each ten inches of tape. As it gets saturated with epoxy, just stack it zig zag atop itself as you keep wetting it out... ending up with a nice zig zagged stack of epoxy saturated biaxial tape. Just start with the biax on your left and wet it out stacking it on the right side of the board.

    Next, just lay it out carefully along the joint and smooth it out with your gloved hands (fingers)... getting rid of all the bubbles. This all goes pretty fast and is kinda messy if you don't work clean.

    Finally, after it sets up a bit (say an hour) ... I apply one more coat of thickened epoxy (one tsp of silica per ounce of epoxy) to the entire joint.

    After cure, use filleting compound to fare the edges of the biaxial tape... and let cure... then use a paint scraper to take off the high points... and sand until fair and apply one final coat of unthickened epoxy.

    The following is a pic of the hull mostly taped with biaxial. The hole in the bow centerline from the large threaded rod still needs to be filled and taped.





    Now here is the bulkhead fabrication process, beginning with what I call "the Tick stick pattern method", which I have used various versions of... depending on the type of bulkheads that need to be built, etc. I thought this method was quite appropriate for this build.

    Note here, the top marking sticks on each side are the exact point that we want the bulkhead to be at upon installation. We want a 5/8" space atop each bulkhead, as that will be the thickness of the sheer decks that will be fabricated and installed once the hull is complete. I did add one more marker stick in the center of each chine here before removing this pattern from the hull.



    Heres the most forward bulkhead pattern that will be the back of the anchor locker. Yes, I know, lots of sticks...but I'd rather use too many sticks then spend too much time fitting a bulkhead because I was impatient and "ball parked it" too much. Lots of sticks, in my experience, make for a very nice fit with minimal block plane fitting. Note on this build, the panels are "tortured" quite a bit to get to the designed shape... which means many of the panels that appear to be straight lines.... are really subtle arcs... which are easier to reproduce in a bulkhead with more points on the pattern form.



    I like to secure the patterns with a method like this, in order to achieve accurate results consistently. Certainly, with epoxy boatbuilding, a looser fit works fine, but it doesn't hurt to have the bulkhead fit with more precision. Note the top stick is held in place at not only the fore and aft position line, but also a 5/8" from the side panel top edge line.



    This is a nice backlit shot of two of the bulkhead templates... in place. This shot also shows my down and dirty quick ply gussets on the main pattern frame... which were minimal and not all that strong, but strong enough for this purpose. The 1/4" Crown staples hold the pointy sticks very well and they are so easy to shoot.



    Heres the forward most bulkhead pattern positioned on the Okoume stock for transferring the shape.



    Continued ...

    RodB
    Last edited by RodB; 06-01-2012 at 12:14 PM.

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