Boat wood quality.

[Smitty]

A thread just below, "Kitsap Lake," describes a boat simply falling apart in the middle of the race. The owner has not assigned a definate cause so far, but it brings a question to mind.

I wonder if the problem with the CSR that disintegrated can be laid to the decline in wood quality and physical properties as denser old-growth trees are no longer available. Bob Rhoades, who built very good hydros in the '60s and 70's, was complaining, toward the end of his days as a boat-builder, that the okoume and gaboon he was getting was poor, "punk-ey" stuff compared to what he had started with.

Are there any old and experienced boat builders (Darryl Sorensen would be one) here who could comment on this? And are there sources of higher grade light plywoods anywhere?

[mdaspit]

Exploding Boat Syndrome

I wonder how much "Exploding Boat Syndrome" there is with boats that do not change climates so extremely.( Florida to Washington State)

How many cases of "EBS" are there in Florida with Florida built boats for example?

[A/B Speedliner]

Wood Quality Now vs Then

I agree, we have been building or restoring boats since 1965 when we purchased the plans and patterns for the A/B Speeliner runabout. The solid Mahogany was probably had 30 per cent greater density. Today's wood is has a lot less moisture content. The Mag. plywood was a dark color, was sold as 1/4", 3/8" thickness and you could counter sink it better. Most boats built today are not screwed together as they were years ago but we still use screws for the ribs and attaching the stringers.

The little amount of Oak wood we use still seems to be consistent with what we used 40 years ago.

Todays consturction uses better adhesives but if care is not taken in mixing the adhesive to the proper proportions the strength will not be there. With fewer metal fasteners used and improper mix or use of adhesives boats could come apart easier now.
David
Aeroliner Race Boats, LLC

[sam]

I bet David is right. So many adhesives and possibilities, staples and machine staplers.

Manually screwed, manually hammered and Elmers or Weldwood take longer and almost no one uses these processes any more for a boat built for someone else.

[Smitty]

One of the changes observed by Bob Rhoades (I wish he were posting here, and Larry Goff as well; those guys were real craftsmen), was that the later wood didn't take varnish nearly as well as the late Sixties wood. One of his tricks (I think I got this from Bob) for getting a smooth finish was to spray a VERY light mist of hot water over the bare plywood to get the surface fibers to lift; as the water dried, you lightly sanded off the surface fuzz and then proceeded with applying your finish.

The report is that the CSR that blew up had dry rot. That is readily believable; dry rot will eat this soft wood like mad. A lot of hydros, especially, have places under the decks that don't get much air circulation and don't dry out well. This is particularly so where the cockpit sides do not have lightening holes, and may even be more or less water-tight, yet there are always drain plugs in the transom, and I think they often seep water INTO the boat. Add to this the fact that the underside of the deck on some boats doesn't get much, or any, protection in the way of a finish coat, and you have a great opportunity for the dry rot bugs to get going.

But I'm still curious about the woods today, and who has access to the best materials.

[Bill Huson]

Ebs . . .

The Exploding Boat Syndrome is caused by MacDonalds, Burger King, Taco Belle, KFC, BoJangles, and s host of other fast food joints.

Let me explain . . .

Our race boats have a minimum weight, and a simple review of physics reveals that more mass takes more horsepower to move aforementioned mass. So a racer hits the fast foods joints and soon discovers their mass has increased (Fat A-- Syndrome) and their rig is overweight. Proper solution, quit eating junk. Usual solution - build a lighter boat! Yeppers, shave down those stringers, knock a few millimeters off the skin thickness, and be judicious with the glue slobbering. Cool, now the FAS racer is on weight. He/she celebrates with a trip to Wendy's and triple deck baconator, large fries, and a jumbo frosty. Oops, FAS strikes again, build another boat, even lighter.

At some point the stress factors hit the limit and we will witness EBS.

[John C167]

Bill;

You shot a "BULLS-EYE" !

[johnsonm50]

I agree, we have been building or restoring boats since 1965 when we purchased the plans and patterns for the A/B Speeliner runabout. The solid Mahogany was probably had 30 per cent greater density. Today's wood is has a lot less moisture content. The Mag. plywood was a dark color, was sold as 1/4", 3/8" thickness and you could counter sink it better. Most boats built today are not screwed together as they were years ago but we still use screws for the ribs and attaching the stringers.

The little amount of Oak wood we use still seems to be consistent with what we used 40 years ago.

Todays consturction uses better adhesives but if care is not taken in mixing the adhesive to the proper proportions the strength will not be there. With fewer metal fasteners used and improper mix or use of adhesives boats could come apart easier now.
David
Aeroliner Race Boats, LLC

sort of a parallel story to construction lumber, 'engineered' lumber aside. Ive been happy with the ply from Harbor but that means buy the top grade & $. A nearby lumberyard has alot of old stock exotic wood from who knows how old but no sitka.

[drbyrne55]

EBS,
I think the cause is multifactorial.
1. There was some black wood ... dry rot? leading to weak points or epoxy breakdown 2. Construction technique possibly did not anchor the cockpit sides to the bottom as well as needed. 3. The boat did not just explode being causally driven. It was at top speed around 65mph and going into a turn under-control but extremely fast. Things came apart when the the turn fin had the load placed on it. This was a load this boat had rarely seen I suspect.

[Jeff Akers]

Ebs

The Exploding Boat Syndrome is caused by MacDonalds, Burger King, Taco Belle, KFC, BoJangles, and s host of other fast food joints.

Let me explain . . .

Our race boats have a minimum weight, and a simple review of physics reveals that more mass takes more horsepower to move aforementioned mass. So a racer hits the fast foods joints and soon discovers their mass has increased (Fat A-- Syndrome) and their rig is overweight. Proper solution, quit eating junk. Usual solution - build a lighter boat! Yeppers, shave down those stringers, knock a few millimeters off the skin thickness, and be judicious with the glue slobbering. Cool, now the FAS racer is on weight. He/she celebrates with a trip to Wendy's and triple deck baconator, large fries, and a jumbo frosty. Oops, FAS strikes again, build another boat, even lighter.

At some point the stress factors hit the limit and we will witness EBS.

Bill, I think what you are describing is called a "Lurking Variable" (A variable that is not included in an analysis but which could explain a relationship between the other variables being analyzed).
But I must say that I have seen mod boats without weight minimums display the same EBS capabilities that you describe. From what I have seen in my short time as a boat racer is, Dry-Rot has been a factor at times, coupled with the age and construction method used in building and also what Mr Byrne has described as "a load the boat had rarely seen". With that many variables I think it is highly unlikely that the wood is to blame or the aforementioned cheesbergerchickenfryedpancackpotatoeatingamerican diet.

I wasn't there and haven't seen the boat so I suppose it could also just be a case of Sh!# Happens...just my 02

Glad no one was injured.

[Tim Weber]

A lot of builders use Obeche for framing. It is really light. I don't like it though.
I have seen Obeche shatter. I doesn't have the fiberous characteristics of a spruce.

As far as the CSR that exploded, I have seen that boat run a bunch of times. It may have had some rot but it is hard to believe that it the only cause for failure. My guess is the fin bracket pulled the chine away and hyrdaulic forces at 65 mph did the rest.

I have a buddy who wiped out a CSR last year that was one of my old boats. It was 2 years old to be exact and it was always garaged, dried after every race etc. He fell in a hole entering a turn and hooked it. He took out the entire right chine, combing, split the bottom in half and broke out the transom. The plywood just shattered. It was hydraulic forces that broke it up.

Let's face it, we are building disposable boats. The construction is way more fragile than in the past.

Tim

[Trihedral_1]

Ocume plywood today is nowhere near the quality it was in the past, and we have to face the reality that the world is in short supply of big trees and the global demand for this stuff is slim to none. You wouldn't need an engineering degree to hold a new piece of plywood next to a piece I got in 1990 to see the difference. Older Ocume 5mm had 5 even plies of solid, clear, top quality Ocume. Today it's 3 inner plies of lower grades (even whitewoods) and two Ocume outer plies. Sometimes the outer plies are just a thin veneer, which is bad. Today's 3mm has about the strength of a Home Depot doorskin, and us boatbuilders need to stay away from that stuff too.
Soooooo, there are only a few solutions: Use thicker plywood & more frames or build with composite materials. That's the harsh reality.

In the Sitka Spruce department, it can be purchase on a scale of "grains per inch", and anything that is sold in "grains per inch" is clearly out of our budgets if we're looking for the strength & quality our grandparents built boats out of. Another harsh reality.

Here's what I did on the last boat: Used Jelutong wood in place of Spruce for the battens/nailers, and reinforced the plywood & things from the inside of the boat with a very light composite fabric in the first layer of epoxy. Without giving all the secrets, it's the same or lighter than a conventional Spruce/Ocume combo.

As for the runabout boat coming apart at Kitsap, I was there and can conclude it was a combination of everything and anything you could possibly ever, ever, ever think of that doesn't involve hitting anything.

Jimi O. (305-R)

[Smitty]

Interesting, Jimi, and sad.

Far too much top-grade spruce has been sold to the Japanese to build their traditional post-and-beam houses. When anyone speaks to them about this waste of the best wood, their answer is, "It is our tradition to build our houses out of clear, knot-free wood!" It's the same arguement the Asians use when they kill endangered species of wildlife, "our holy tradition!!" I like those people, have lived in Japan (with a house-builder). But we should have told them to stuff their tradition a long time ago. There are higher and better uses for the best woods than house construction.

Now that it's nearly too late, the authorities have tightened the rules so much, I'm told, that even if you have plenty of old growth spruce on your own property in southeastern Alaska, you can't legally cut any of it to build yourself a cabin. It is done anyway, on the quiet. Maybe the APBA should arrange with some bribe-able property owner to cut down one big old-growth spruce tree and put it on a barge. One big tree, dried and sawed might supply raceboat builders for a long time!

Presumably, Aircraft Spruce and Specialty still gets the good stuff, since you wouldn't want anything less in your homebuilt plane. Probably they have FAA approved aircraft birch plywood as well, but that's on the heavy side for us. OTOH, some guys (Don Foti was one) used to build their boats out of Utile, which is relatively dense and heavy . . . or used to be (Jimi?).

A long time ago, Ed Karelsen, asked about whether raceboat grade Philippine mohogany plywood could be had, offered the general advice, "You can get anything if you're willing to pay enough." Ed wasn't just talking; he had talked U.S. Plywood into making him some 30' sheets of plywood for the Bardahl.

[seanp3]

As far as the CSR that exploded, I have seen that boat run a bunch of times. It may have had some rot but it is hard to believe that it the only cause for failure. My guess is the fin bracket pulled the chine away and hyrdaulic forces at 65 mph did the rest.

Tim

Photo of the EBS. At this point the cockpit, motor and driver are underwater

[DeanFHobart]

Two British Standards

To All,

There are two British Standards for Marine Plywood.

BS 1088 and BS 6566. BS 1088 is the best one which calls for all the plies to be the same thickness. BS 6566, the outer plies can be thinner and the specification says how much thinner it can be.

Make sure you are using actual BS 1088. There is no requirement for a manufacture to use any particular standard...... maybe even some manufactures might stamp on BS 1088 and it is not actually BS 1088.???

Some of this plywood is being made in China.

Bruynzeel Okume or "Gaboon" also called Joubert Bruynzeel plywood is the best and will be for sure BS 1088.

Available at Jamestown Distributors.

Both specs are available on line. BS 6566 says the outer plies can be thinner.

Don't save money and buy the cheaper stuff.

Good Luck.