are we building boats backwards

[tx river rat]

Micks mishap got me to thinking, are we bracing our boats the wrong way we put a lot more glass and resin on the outside than we do the inside. Some of us are just tapping the seams and epoxy saturating the wood on the inside, putting heavier cloth on the outside more coats of resin the epoxy and graphite
If you take a piece of ply glass both side then hit it with a object it will bend and the fracture on the side opposite the force of the blow (inside the boat) the side that takes the lick can give the opposite side is under tension just like the face of a bow it stretches till it breaks, maybe we need heavier glass on the inside and lighter on the outside where wear is more important.
My boats are built with 4 mm bottom and 3 mm sides so far so good.
maybe we should be thinking outside hull built for wear inside hull built for strength
Ron
What you think guys

 

[oldsparkey]

Anytime a boat and a rock meet , the rock usually wins , hands down. Aluminum boats get dents , fiberglass cracks , plastic gives way and gets scratches , most of the time.

I did notice from Micks pictures that the bottom got a good scratch and it appears that's what caused the problem , the bottom flexing to the cracking point. If it would not of flexed then the damage could of been a lot worse like having a big hole where the crack is.

When a moving object hits a non moving , well anchored , stationary , object the moving object suffers. The trick is to avoid the rocks , when possible.

Chuck.

 

[oldsparkey]

A case in point .......

When paddling the canoe down the Buffalo River with Bear and the gang , running threw one of his little rapids ( it looked like Angle falls to me ). I heard this LOUD KRACK in the area of the bow , which increased the pucker factor 100 fold.

I had water running from the bow to the middle where I was seated. I keep bailing and paddling till we got to the campsite. After taking everything out of the canoe and checking it I could not find a crack , hole or anything that was damaged. Later I realized the water was coming from a cloth bag the tarp was in at the bow of the canoe. The water would splash over the bow , fill the bag and then it leaked the water out making me think there was a hole up there.

Getting home I sanded the graphite off the bottom to check for cracks ( a job I would not recommend to anyone) Then checking the inside I still could not find a crack anywhere in the canoe. I redid the bottom with the graphite and double checked the canoe.

All I can figure is that it was one of the stringers (running the length of the canoe) I have epoxied inside over the seams of the panels to beef up the bottom complaining but never did give away. Only thing I can figure is that one or more of the stringers ends gave way which are sealed in the bow behind the bulkhead under the short decks I installed to seal about 9 inches of each end.

To make matters more interesting the canoe is only glassed (3.25 tight weave ) on the outside , epoxy saturated on the inside.

All that happen on the 2005 trip and to this day I have not found any cracks or anything loose in the canoe ( except for the paddler) . Trust me there was a loud Krack going over that one rapid.

Chuck.

 

[Kayak Jack]

Both Ron and Chuck have good points. What Ron is saying, I think, is that if you strongly reinforce the INSIDE of a boat with epoxy and glass, when the wood is severely flexed by objects from the outside, there is less chance of ultimate wood failure.

What this is can be simulated by a green stick fracture. Bend a green twig and it will fracture on the OUTSIDE of the bend. In a boat bottom with an object - especially a pointed object - pressing up from the water, that break would occur on the INSIDE of the boat. That is why extra reinforcing there can help prevent the kind of fracture experienced by Mick.

No guarantee, only increased resistance. John Lockwood of Pygmy Boats wrote of exactly that same phenomenon when he was designing his first prototypes. And he solved the problem with epoxy AND glass on the inside of his boats.

And, while we're on the subject, this is only one of the reasons for using a tent liner INSIDE the tent rather than outside.

 

[oldsparkey]

Ron...
I'm sure you will figure out the correct way to improve the situation and make a stronger boat. I can hear the wheels turning all the way over here.

Just as sure .... I'm positive Mick will come up with the answer to repairing his boat since he built it and really loves to paddle it. I can't see Mick letting it sit in the corner gathering dust and not be repaired and used in the future.

The information the two of you decide on will benefit all of us on here and we await your answers /solutions to the problems. If not you can bet there will be more suggestions to help you decide.

Chuck.

 

[tx river rat]

I did a poor boy test on some 1/8 ply today
four pieces 18 in bye 6 inch
1- 6 ounce on outside 4 ounce inside


2- 4 ounce outside 6 ounce inside

3- no no cloth outside 6 oz inside

4- no cloth outside 4 oz inside

where I had no cloth i has resin the same thickness as with the cloth
I took the corner of a piece of one inch ply and used that to push on

number 1 and 4 broke with close to the same pressure
nu 2 and 3 also broke about the same the cloth on the outside didn't seem to help.
I laid up one more and it was the strongest resin on outside and 4 oz inside then another 4 ounce laid with strands at a 45 to first piece
that piece was tough, it took several times the pressure to break it over any other sample.

Just from these simple test I think a man could build a tough boat tapping outside seams then laying on the resin and epoxy with a little heavier cloth on the inside or the toughest 2 thin layer of cloth.
Ron

 

[Ozark]

Interesting test Ron.

 

[hairymick]

G'day guys,

Good post Ron and thank you for going to the trouble of doing the destruction tests for me.

Chuck has hit the nail squarely on the head. I will be fixing my Laker and will be starting tomorrow. She is just a too good to let sit idle.

Laker took a LOT of abuse the other day before she failed. Where she cracked was just in front of the seat - under my knee on the starbourd side.

I think there is a reason for this happening where it did. Part of that reason is that the way my boat was loaded, that was where the boat was least able to bounce off the rock.

I bounced and scraped off a lot of other rocks that day with no damage apart from scuff marks in the graphite.

My Laker was fully glassed inside and out with 200 gram cloth (not sure what that translates to in ounces) But I plan to re-inforce this area significantly, using the tips and ideas posted in the other thread - thank you pluss a couple of ideas of my own. Will post details in the other thread as I go.

I have taken on board Matts comments re the plastic jobs being more suitable for genuine white water, but simply put, there is no joy for me in paddling such a boat anywhere. If I need to build more boats, or build them stronger then so be it. (bring it on!!) :lol: The two plastic boats on our little trip were the only two to come through relatively undamaged.

Thanks again guys, I just don't have the words to describe how I feel about this place. 8)

 

[oldsparkey]

G'day guys,

Thanks again guys, I just don't have the words to describe how I feel about this place. 8)

Mick .....

Thank you for that statement , we do not like negative publicity or exaggeration of the facts and I appreciate you refraining yourself in that aspect .... OK , I can see you saying to your self , what is he talking about.
Darn if I know except that we are indescribable which I'm sure everyone will agree on . :lol:

"O" Well .. I knew you guy's would come up with a good answer .. I have faith in you since you always have the right solutions to most problems ... Bet ya thought I was going to say all of them. :lol:
Or is it you guy's just leave a few out so the rest of us can shine...........

Either way it is a win... win for everyone. I was going to say keep up the good w&%k but I think fun is a better term.

Chuck

 

[JEM]

I have taken on board Matts comments re the plastic jobs being more suitable for genuine white water, but simply put, there is no joy for me in paddling such a boat anywhere. If I need to build more boats, or build them stronger then so be it. (bring it on!!) :lol:

For running in white water with rocks in a wooden boat, something rounded, with plenty of panels would survive the best.

 

[tx river rat]

Mick and Matt
I think you can build a whitewater boat out of wood if you build it to the weight of the Tupperware boats and like you said round , I have hit rocks in the Brazos a few time so hard that it would really jar you and if there had not been foot braces I would have been out of the boat. The plastic boats if run in rocks will cut split and wear out . And ours are easier to fix
and so much lighter and prettier.
I have had to fix one thing on a boat and I use them hard , but I had to fix stuff on my aluminum air boat and my glass boat they all need maintenance.
Love these wood boats
Ron

 

[hairymick]

Mick and Matt
I think you can build a whitewater boat out of wood

So do I mate!

I am not looking for a boat to acrobatics or the other nonsense, Just a boat to run the white water safely with a minimum of fuss. The boat still needs to be a reasonably good paddler cover distance on flat water as well.

The problem with our Mary is that at the end of the last rapids, there is about a 8 mile paddle to the take out with few places in between where we can put ashore for a break. Steep to banks, heavily covered in bush with no sand bars.

Matt Wrote

For running in white water with rocks in a wooden boat, something rounded, with plenty of panels would survive the best.

Yes, I think so too. Our rapids on the Mary are not big water by any standard but there are a lot of them.

I am talking with a nice lady who owns a farm on the banks, way up in the headwaters of this river. Am going there for a visit this Sunday and hope to be able to arrange access for an extended, multi day trip in the coming months. If all comes out the way I hope it does, this river is going to be paddled much more often.

Hope to get some piccies of our endangered lung fish

 

[jdupre']

Ron, your tests make sense. Hitting any hard object with the hull will put the inside surface under tension until it fails. I've built a bunch of bows out of wood backed with fiberglass and some all wood bows. The few that failed all failed on the back of the bow ( the part oppsite the side you look at as you shoot). Most bow designs allow for this by putting stronger wood, glass, sinew or cloth on the back of the bow.

So the ultimate hull might have enough glass and resin on the outside to protect against abrasive damage and enough on the inside to protect against blunt force punctures. It's always a balance, isn't it?

Joey

 

[tx river rat]

Joey
Thats what started me thinking about this I have built a lot of bows and the face (front ) of the bow has tension the back is compression, hardest bow to build is an unbacked wood bow .
Ron

 

[jdupre']

Ron, I think Mick's boat did what it was supposed to-- take everything you can throw at it and still get you home. From the looks of the crack, the glass fibers did not break on the inside- just got pushed up at the site of the crack. They spread the pressure over a wider area and prevented a punture. That's about all you can expect a boat to take and still be light enough to carry and paddle easily. You could build a boat that would never fail but it might weigh 150 lbs.

 

[rhutchinson]

I don't know anything about fiberglass, but....should biaxial or triaxial cloth be considered for potential impact areas? Thats pretty much what TRR did on his last sample isn't it?
Richard

 

[seedtick]

there's more than one way to skin a cat and there's even more ways to build a boat.............

have any of you thought about building a boat out of 1/4" marine grade plywood instead of those 1/8" door skins. Adding 2 1/2 galons of epoxy and 15 yards of glass seems like a lot of extra trouble just to get a stronger boat. If i remember strength of materials stuff, wood strength goes up as the square of the thickness. So 1/4" is 4 times stronger than 1/8". If you use good materials. it's likely more than that.

 

[JEM]

seedtick speaks words of wisdom. Pound for pound, nothing beats what mother nature produces.

Exception would maybe be carbon fiber but that's some expensive stuff.

Wide and flat panels are tough to make super strong. Best way to get good stiffness would be to add a chine to the design.

To get the full effect of a composite sandwich, the core thicker the core the better. But if you try to do this with wood as the core, thicker wood needs less glass to support it since the woods stiffness contributes to the strength of the composite sandwich.

 

[bearridge]

Fellas,

If ya'll make a homemade boat, under 30 pounds, that kin handle hittin' a big rock, fulla water at 4 mph....we kin talk. :mrgreen: :mrgreen: :mrgreen:

regards
bearridge

Flabbergasted (adj.), appalled over how much weight you have gained.

 

[hairymick]

G'day Ticky,

Good points mate.

I don't think strength is so much the issue as is impact resistance.

My Laker did what she was supposed to do in that I was still able to paddle her back to the take out in spite of the damage. This saved me a walk through heavy bush of about 12 miles from where I hit the rock.

At the moment, I am leaning towards a boat with bottom panels at 1/4" to about the waterline and 1/8" above that. This might prove a little problematic in a multi panel hull requiring torturing the panels into shape.

I think a Laker type hull with 1/4" bottom panels with 1/8" sides and deck would be fairly easy to build and make very tough for not a great amount of weight gain. Added strength of the thicker ply bottom plus heavier glass inside and out should combine to make the boat dis-proportuionately tougher than the same boat made with thin ply and very light glass Will probably add 10 pounds or more to the total weight of the boat but that is fine by me.

I am thinking of a possible boat that might suit pretty well re ease of build is Matt's T-V. Slightly more complex build with the heavier ply bottom could also be something like Matt's Issaquah 14 or a 14" version of Sasquatch.


Aaaah, so many boats and only one life time to build em in :lol: