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Midnight wondering from the Ch. Mate

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I spend half my life on ships and have a considerable amount of time to think about "stuff", what better a place to get answers than here!

1. Epoxy listed on BOM's, is it total volume or gallons of resin sans hardener. example my Spindrift listed approx. 3 gallons needed is that 3 mixed gallons or 3 gallons of epoxy resin?

 

2. Is "sharpening" the chine on a Spindrift necessary as I have seen on the larger powerboat builds? 

 

3. How do they do the teak or Mahogany transoms on big Sportfishers? is it full thickness planking or a veneer of 3/4 to 4/4 attached to the "real" transom, is the end grain inside the hull planking to hide it? but then you get the end grain of the ply/solid planking?

 

4. Stability and Weight Calculations - The USCG says a "person" weights 185 pounds, however we recently had to adjust the capacity of our lifeboats as I work in the oilfield and a large portion hahah  of our personnel complement is in access of this number. We have one guy who is 6'8" and about 415 and not that fat, the dude could fold your clothes with you in them. Hell, I'm 265 of twisted steel and sex appeal myself! Do most designers in america use more realistic numbers for calculating capacity?

 

5. Wood, I always see Douglas Fir as being a wood of choice for many designs; B and B says SYP (good stuff not junk) as a good wood, which I agree with, but I often have plenty of Cypress around from carpentry projects, but the ol' interweb seems to have widely different opinions about this- Whats yours?

 

6. Paint, What is the best? not for the money, not for a budget - the best. I have painted literally acres and acres of steel over the years and find International Paints Intertane 990 two part epoxy hands down the best at least for commercial applications. We currently use Jotun which is junk. I could not believe it when I started learning stuff, that guys were buy paint in quarts! The last paint job I did on a ship involved 120 gallons of primer and 80 gallons of topcoat! and that was just about a quarter of the deck! I have no problem spending money on paint, all my hardwork and time is NOT going to be sullied by cheap paint, plus I know first hand its worth it in the long run, spend two weeks on a 40,000 psi UHP water blaster wearing armor in the gulf in the summer will really make you think about high quality paint- not to mention running the devils own invention, the needle gun!! 

 

Let'r rip and sound of with your opinions maybe lots of people can learn from some of these dumb questions. 

Hulsey 

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1. Combined, total volume

2. No, it only really helps with high speed planing and a round corner is more forgiving of damage.

3.  Any and all of the above.  My Lapwing transom is Sapele BS 1088 ply.  Thin material can be added at a weight cost. Where the end grain is not appealing, I do this.....

(see photo)

4.  Good question, not for me to answer.

5.  Most of the solid wood on these boats can be almost anything.  Some things should be hard as in gunwales.  Most  will be epoxy encapsulated, the rest can.

DSCN3735.JPG

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Pretty, pretty boat. 

 

A follow-up question to his #5.  I have a friend in the millwork business that gave me tons (literally) of Sapele.  It's tailings and off-cuts from a huge project.  Not very big in dimension (1x1 and 1x2, or less), but most of it is sixteen feet long.  Is there any reason not to use it anywhere on a boat?  So far, I have steam bent it and used it for ribs on my OB20 build.  It seems to split, if my screws aren't right in the middle, but that's my fault and would probably occur no matter what species.

 

 

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Regarding the paint question; I should note that I live in Northeast Florida and spring is coming, bringing with it high temps and humidity.

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1: You got it right, if you need 3 gallons and it's a 2:1 mix, you'll get two gallons of resin and a single of hardener.

 

2: As mentioned above, sharpen the chine if the boat can get up on a plane, but if not, then rounding will ease water flow and be easier on your knees when you bang it into one.

 

3: There's a few different ways to do a "bright" transom, but most commonly on small craft, it's a nice looking piece of plywood, carefully taped off and varnished. I've done veneers and also more traditional solid wood transoms too, but these require more work and more costly materials, for just an aesthetic gain.

 

4:  Stability and weights are part of the design process and yes we do use standard "crew" weights, though it typically wouldn't be 185 lbs. on a cruising boat, more like 205 (you're going to bring stuff along with you), but on a performance oriented craft, 185 would be more likely. In reality, it's a bit more complex, but generally for small pleasure craft you work around a "typical" total crew weight, not a per person weight. For example, a 14' performance dinghy, may have a minimum 185 crew for optimum performance maybe less. This would suggest it's a solo sailor and the other elements of the design would reflect this (beam, draft, sail area, etc.). It can sail with two aboard, though the weight over 185 will progressively detract from it's performance envelop. On the other hand if you have two kids aboard . . . Boats are designed around volume, using shapes to meet performance expectations, more so than the weight of a crew member.

 

5: There's good and bad things to consider about any species you might want to use. Douglas fir and SYP are fine woods, as can be some of the cypress available, but it's more about recognizing what a good and bad hunk of lumber looks like when you pull it from a pile. In the end it's usually best to try to match the physical properties of the species spec'd in the plans with something similar, though more available in your area and of course select an appropriate piece for your rub rail or stringer (whatever).

 

6: There's no best of anything really, though there are lots of choices. In a perfict world, we all would use epoxy primers and solvent based LPU's, squirted with a HVLP gun, for a perfict, hard durable finish. Then reality steps in and you realize it's not the paint so much as the prep, which is 90% of the paint job. No sense putting $300 a gallon topcoats on,  if your skill levels make it look like it was applied with a wire brush. I actually have $600 a gallon paint here in the shop and I put $1,800+ of labor into each. For the backyard builder a good quality, name brand single part polyurethane will do a fine job, especially if you really work on the prep. Good prep can make the cheapest Ace Hardware latex house paint look great, but so, so prep can't make the "best" paint look much more than something only a mother can love.

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I am becoming aware of the fact that various wood species do not bond the same, when using epoxy. I’ve heard that White Oak “lets go” over time, and that Cypress “does’t take glue”.  Does anyone out there have the real story on wood/epoxy compatibility?

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Thrillsbe,

I too have heard that about cypress, I assume it is due to the fact the Cypress contains cypressene which is an oil and contributes to the decay resistant properties. I have glued it down with hardwood flooring mastic ( 1000 sqft in my house ) and used Gorilla glue with it on outdoor projects and it glues just fine. I have researched it quite a bit and it is a 3 out of 5 for glue-ablity or referred to as having good gluing properties. It is less dense than SYP which I can attest to, when green it is very easy to work. Cypress is also prone to "ring shake" where the annular rings separate from the heart, however I have only seen this in beams which I build pergola's with. But with epoxy Im not sure, I think it would make great ribbon material as it is flexible but strong in my experience. 

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I don't understand this cypress thing. I used cypress to plank my 28, with no issues. It quite simply drank in the epoxy like water at first wetting. Maybe it was the species of cypress that I used. My way of thinking is if you have a chemical bond from deep in the wood to the outside of the glass sheathing,  is the best it gets.

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The key with oily woods is to clean the mating surfaces with a strong solvent immediately before bonding.  I use acetone on Teak and White Oak and have never suffered failure.  Acetone dissolves oils well and dries almost immediately.  You can glue up within minutes, even in cold temperatures.  Mill, fit, dry clamp, yadda, yadda, then clean with acetone and immediately glue up.

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Dave has it right, some of the oily woods need additional prep, which is as he describes a scrub with solvents to remove the oils, just prior to goo application. I have a few different chemical combinations, but they all do the same thing, remove the oils. Since discovering this, I've never had a failure either. The other problem with cypress is it really likes moisture, so any coating and/or sheathing needs to be robust, as any moisture gain can quickly open a check or "move" the wood enough to spit off any glue, coating or sheathing. Douglas fir plywood is like this as well, though not to the same degree.

 

These are all things you need to learn, preferably not the hard way as most of us already have. Learn about wood, how to select a good piece from a pile of lousy ones, grain orientation, run out, physical properties, preferred species and any special prep that may be necessary, etc. It'll save your hair.

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In about 1950, the accepted USCG weight for boat calculations was 150 - 155 lbs. Then came the good times, every one started eating the bad stuff, too  much of that and the current obesity trend was underway.  The USCG is having a hard time keeping up.  The number has advanced at least 20 lbs since I started using it as a design factor.  I'd use my own judgement for any specific case and the latest USCG number for when that is important.. 

 

Cypress is a mixed bag.  Heartwood is rot resistant but usually has lots of knots.  Sapwood is often clear but not so durable. 

 

At first glance, I thought I was looking at "Lapwing" but then saw that it was a Lapwing even though it has my top strake scroll carving and shape.  Graham put it in the computer I guess.  Very nice anyway.

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So all of your questions have been well answered.  I just wanted to answer the specifics of question 3, the bright transom on sport boats.  I spent a good portion of my young life working on these boats and the answer, as always, is yes sometimes.  

 

Newer boats would be veneered with 4/4 or less or even vinyl wraps.  Usually there is a step in the transom planking/layup at the boot stripe.  The transom planking/veneer would then be glued to the existing structure and all would be planar.  All of the boats I remember had the end grain exposed, so the topsides paint would end at the glue line or a bit onto the transom planking.

 

Older builds would have mahogany/teak planking as a part of the structure connected directly to the transom framework and would be finished bright.

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Thank you all! really appreciate the time and effort to satisfy my wondering. Now what to build next..................I'm not even done with my Spindrift, but the end of it is in sight and I am already looking ahead! I think something with a engine at least, I need a skiff of some type for fishing and knocking about. I had a 25 Mako several years ago before the crash in the oil field removed all luxury items from my life,  it was pretty spendy to own and run. Until oil is back to 80-90 a barrel, Ill be fishing the oysters bars and creeks - not the Stream

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