First build

Hi everyone, I'm just getting started.  I've gathered all the tools, read Fletcher's book about 6 times (so great), and read quite a lot of these posts (also great).  I've decided to build a 17x54.  Went to the lumber dealer in town, and decided i'm definitely going to use the Hydrotek BS 1088 6mm for sides, and 12mm for floor.  I'm going to use Mahogany for the Stem.  I'm planning to use Port Orford Cedar for the frames, and was thinking i'd match that with White Oak for the rails/chines.  I hope to have the boat for the rest of my life, and while i want it to be the most beautiful boat ever built, I truly want to use materials that will last and be effective.  So, first question... Instead of White Oak, anyone ever use Port Orford for rails?  It seems like the color would be similar to White Oak, but i wonder about durability as a rail.  appreciate any insight you might have.

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Permalink Reply by Gregg Maddock on December 10, 2019 at 6:05am

Dusty, I ‘glassed the bottom of my last 2 boats. The first was 14’ with 3/8” bottom. The second was a 17’ with a 1/2” bottom.  While both have added strength I did run into one problem on the 17’ boat.  While the 3/8l bottom went on fairly easily, I had extreme difficulty mounting the 1/2” bottom on the 17’ boat.  It just did not want to bend once it was ‘glassed. The 3/8” bottom was not a problem.  If I was to do it over I would not of ‘glassed the 17’.  

Gregg

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Permalink Reply by Dusty on December 10, 2019 at 9:01am

glad you mentioned that Gregg.  Maybe 6 oz glass the inside before mount, then glass the outside after mounting?

Permalink Reply by Rick Newman on December 10, 2019 at 12:10pm

Dependent upon the amount of fiberglass and its' weight the greater or lesser the ability for it to bend. I laminated at least one layer of 18 tri-directional glass on the inside of my floor as did Gregg.

I had to use multiple ratchet straps, lots of weight and decrease the distance between the screws holding it down to make the boats' bottom to the boat.  It took a lot of effort to get it mounted, but I wanted to have a bombproof floor that was greatly strengthened because of the strength of the glass.

My reasoning was that I wanted to make my boat more resistant to a puncture so that if I hit an immovable object my boats' floor would be to resist a puncture and spread the stress out throughout the installed fiberglass. I did not want to have to repair a puncture in the field taking time away from floating, rather spending the time at home if needed to do the repair. I would rather apply a few strips of duct tape in the field than having to do a fiberglass repair.

Adding a stiffener to the inside of a panel can greatly increase the ability of that panel to prevent fractures or punctures because now the fiberglass resists bending hence adding strength. Fiberglass laminated to the outside of the floor reduces the damage caused by abrasion on rocks, metal or other abrading materials. When both sides of a material have fiberglass laminated to it increases the strength, even more.  If the thickness of the panel, is doubled, say 1/4" to 1/2" the strength of a laminated item will increase by a factor of four. Adding a stressed skin to the inside of the structure will then even further increase the resistance to a puncture. A stressed skin laminated to the outside of the structure does not add measurable strength to a structure only resistance to abrasion.

Rick N

Permalink Reply by David Witton on December 12, 2019 at 6:33am

One approach that hasn't been mentioned in this thread is the combination of plywood, glass and a honeycomb material like Nida-core. It combines ease of construction with impressive strength - I attacked a test panel with an 8 pound sledge and was very impressed. 

Permalink Reply by Shawn Baker on December 10, 2019 at 1:41pm
I agree with Rick, and I think he even posted similar advice when I was planning my own build. I had a hard time bending half-inch plywood on my floor and glassed after it was in place. I can only imagine how difficult it would be to bend with one or two glass faces!
Permalink Reply by Shawn Baker on December 10, 2019 at 2:08pm
If and when I build another with a composite floor, I will strongly consider laminating two pieces of quarter inch together to make the bend.

1/2” fir ply has 5 plies.
1/4” x 2 will give me 6 plies and an easier bend.
Permalink Reply by Bennett Yarbrough on December 12, 2019 at 6:33pm

What if you did a 1/4 inch ply, 12-18 ounce triax, 1/4 inch ply sandwhich? Don’t think it would be as strong as glass on 1/2 inch but may be a bendable happy medium?

Permalink Reply by Don Tyson on December 21, 2019 at 12:08pm

Has anyone mentioned popping the floor out a bit to give it a positive hump across the boat. In stitch and glue constuction it is easy to accomplish as you simply add 1/8" spacers to the middle of the frames for much of the length. this prevents oil-canning, builds greater strength and some say better turning. it is such a small amount that you really have to look for it to notice. I know that when I discovered Drift Boats earlier this year I was online looking a tenders and prams for river use and they all have defined dead rise of several degrees making them much stronger. Perhaps on Driftboats you want things to flex a little more here and there and to keep them as low as possible.

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Permalink Reply by Dusty on January 12, 2020 at 8:15pm

After about 8 hours of belt sanding (two 7 foot joints), I've decided I will never belt sand another scarf joint.   I will get over my fear of the router/jig method.  


Permalink Reply by Shawn Baker on January 13, 2020 at 7:56am

It took me longer to convert my worm drive saw over to my handmade jig (had to remove the base shoe to get 1/2" deeper cut) than it did to cut 10 scarfs!!

a big 7" grinder with 60-grit will also hog a lot more material faster than the belt sander.

Your scarfs are beautiful though, Dusty!

Permalink Reply by Dusty on January 12, 2020 at 8:29pm

btw, catching up on a couple images.  Chines installed, and fared.  Steaming made it super easy, 3/4 inch white oak chines.

In retrospect, i should have put more time into making certain the notches were at proper angles to receive the chine.  That wasn't fun to fix.  

Permalink Reply by Shawn Baker on January 13, 2020 at 7:08am

How did you fix the notches--pull saw?

I'm at a similar stage on a 1:6 model Woodie Hindman 16' double-ender and made the notches backwards on a couple of my frames *duh!*...but the model frames are ~10" wide at most and are easy to cut on the bandsaw and angle in the disc sander.

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