New Boats--Let's see em

[f8andbethere]

If flexing is such a good thing, why don't you leave some crossframes or stringers out of your next boat and see how it works? Or find some 1.5 mm ply for decks? Or mount your steering wheel on a pedastal rather than a dashboard that ties the cockpit sites together?

While ride "feel" may be nice for a driver, the purpose of a hydroplane is to go around the race course faster than the other guys. Funny you didn't mention anything about the actual performance of a stiffer hull, only a subjective quality virtually irrelevant to the major mission. As one who has many times put new decks on a 3-5 year old boat to stiffen it up again and see a performance gain in cornering, I know stiffer is better! Perhaps you can get to the point where it would be too stiff, but I can't imagine that in my experience. Guys spend hours working on their bottom contours just right, only to want their hull to flex and distort their work? I don't think so!

The thread was on who uses what species of wood and in response to some guy who claimed that Sitka spruce was god's gift to hydro builders. It was to point out that most testing for wood samples was done on a size basis but that lighter species may have better properties when compared on a weight basis and that weight is more of a concern to us than size. I gave some engineering basis for this. It seems that most hydro builders are using lighter woods than Sitka already, yet some guy without a record of building contemporary, winning hulls still says that Sitka is best. If you want to believe someone's opinion, good for you. I'd rather believe actual facts, figures, math and results.

Agree with everything you have written --though I could do with a little less sarcasm. However, the bottom line for bottoms is aluminum honeycomb. It is a skosh heavier than 1/4 inch bottom plywood of choice but is 10 times stiffer and it will allow you to do away with some stringers and deck frames which in the end will give you a lighter boat.

RB

[G Stillwill]

Some pics of the B Mod Hemp kit Im building for Ron Selawach and next is a Hemp BSH kit for myself.

[raceboat61-S]

OUCH ! I appreciate you're fine post on the properties of various woods and the engineering considerations necessary in hydro construction but your response to my comment about enjoying some flexibility was a bit over-reactive. I built my first BU runabout in 1960....am currently building a 25 Mod/SSH hydro of obeche and okume. I have met with some success in the shop and on the race course. I still enjoy racing both runabouts and hydros in about 7 different classes. At 61 years old, I appreciate a bit softer ride. I enjoy the natural flexibility of my wood/epoxy boats. Mike Marshall, Raceboat61-S

[hydroplay]

If flexing is such a good thing, why don't you leave some crossframes or stringers out of your next boat and see how it works? Or find some 1.5 mm ply for decks? Or mount your steering wheel on a pedastal rather than a dashboard that ties the cockpit sites together?

While ride "feel" may be nice for a driver, the purpose of a hydroplane is to go around the race course faster than the other guys. Funny you didn't mention anything about the actual performance of a stiffer hull, only a subjective quality virtually irrelevant to the major mission. As one who has many times put new decks on a 3-5 year old boat to stiffen it up again and see a performance gain in cornering, I know stiffer is better! Perhaps you can get to the point where it would be too stiff, but I can't imagine that in my experience. Guys spend hours working on their bottom contours just right, only to want their hull to flex and distort their work? I don't think so!

The thread was on who uses what species of wood and in response to some guy who claimed that Sitka spruce was god's gift to hydro builders. It was to point out that most testing for wood samples was done on a size basis but that lighter species may have better properties when compared on a weight basis and that weight is more of a concern to us than size. I gave some engineering basis for this. It seems that most hydro builders are using lighter woods than Sitka already, yet some guy without a record of building contemporary, winning hulls still says that Sitka is best. If you want to believe someone's opinion, good for you. I'd rather believe actual facts, figures, math and results.

[raceboat61-S]

Flexing

Flexing is usually a GOOD thing. Racers that have raced both the brittle pure carbon fiber boats and wooden boats will tell you that flexing gives a better ride. If weight is critical for your boat/motor/driver combination you may have to sacrifice the "ride" a wood/epoxy boat will give you.
Mike Marshall Raceboat61-S

[MN1]

Wow. That last post on wood really got my attention! I find it very interesting that people use such a wide variety of wood for stringers and frames. The last couple of seasons I have put a video camera on the dashboard of my D stock hydro. Over the last week or so I have gone back and watced the tapes taken, and I am blown away by how violent the impact is when going into a corner at 80 mph...I always suspected that the right sponson acted like a shock absorber on a car....moving a little to absorb impacts. To my suprise, the tapes show the sponson moving (bending) at least 3 inches! This makes me wonder if the type of wood used, and the thickness makes a performance difference.

I know how to reduce the flexing of the boats. And it has nothing to do with stringers. In fact, I can make your boat as stiff as if it had decks on with no decks on!!!! It takes more time but is worth it. Email me if you are interested.
Mark Nelson

[daveracerdsh]

Party

Lol...the strongest thing I had a party was coffee....I went to shop right after and worked on new boat and didnt wanna have any booze in my system. I am making up for it right now though....drowning my sorrows in booze!

[mrlou40]

[QUOTE=daveracerdsh;70936]Wow. That last post on wood really got my attention!

Could that have anything to do with the bloody Mary's at J-Dubs Sea hawk party today??????

[daveracerdsh]

Info overload

Wow. That last post on wood really got my attention! I find it very interesting that people use such a wide variety of wood for stringers and frames. The last couple of seasons I have put a video camera on the dashboard of my D stock hydro. Over the last week or so I have gone back and watced the tapes taken, and I am blown away by how violent the impact is when going into a corner at 80 mph...I always suspected that the right sponson acted like a shock absorber on a car....moving a little to absorb impacts. To my suprise, the tapes show the sponson moving (bending) at least 3 inches! This makes me wonder if the type of wood used, and the thickness makes a performance difference.

[hydroplay]

I've used a number of different woods for the framing of hydros. My very first boat was made with Sitka spruce because the "experts" claimed it had a superior strength/weight ratio. Of course I assumed they knew more about wood than I did so I went over to McCormick Lumber in Madison and bought a board. Their stock was all over 12 inches wide and 44 feet long. The boat turned out fine but I wasn't horribly happy with the Sitka. Its a northern wood so has hard and soft areas from the winter/summer growths. It also was hard to rout/round edges. So I became open to trying others, including Douglas fir, obeche. Atlantic white cedar, northern white cedar, lauan-particularily white luan with selected boards, basswood, redwood and a few other less-well-known types.

Currently there is obeche, Northern white cedar and basswood in the shop. Obeche is generally a great wood although there can be a difference in board weight, hardness and grain structure. Knots are virtually non-exixtant. The downside is that it is very dusty to plane and cut and can cause allergic reactions.Years ago I became allergic to it and didn't use it for some time but tried it again and found I could tolerate it again. It is stiff for its weight and glues/shapes well. It also tends to shatter on impacts rather than split like spruce and fir so that damage from crashes is somewhat localized.

I used to use quite a bit of Atlantic-not Eastern- white cedar (juniper). Its a Carolina swamp tree but you had to work around knots at times. I later found a good source for midwest white cedar from old telephone poles. This wood is great to use because the poles were straight and well preserved after years of use. But cut away the outside and there is wonderful, clear, straight and dry wood inside. It also has a far more pleasant smell than obeche. I can do my part for ecology and recycling so I don't have to feel bad about using gas on my truck to haul the race boats around and race them.

My experience shows that these relatively light and stiff woods are superior to the heavier spruce, without question in race boat use. While spruce may be rated high in strength to weight, the simple test people love to quote for this uses a standard size test piece, weighs it, determines the stiffness and simply divides it out. This test may seem relevant but it eliminates density and geometry, both of which are significant in real- life situations. Far more useful informative is gained from running the same basic stiffness check for various woods but using samples of the same given weight and width, the height varying to give equal weight test specimens. Of course they don't do this because it would take a lot more work to make equal weight samples that have a commom width and length. Even then, moisture content will affect weight so heights must be altered if the moisture content changes. The stiffness of any particular beam, stringer, spar- whatever you want to call it, is proportional to some constant for the particular wood x the width of the piece x the height cubed. This cubing of the height property can be used to give magnificant increases in stiffeness without any increase in weight if you simply use a narrower but higher beam. Given this geometrical input, a beam of a given weight and width of obeche will be stiffer than a beam of the same weight and width of Sitka spruce. The obeche may break with less energy but none of the wood framing in hydros is loaded heavily enough to break in ordinary service. Stiffness and strength are not the same qualities and I find stiffness far more valuable than absolute strength.

Consider two beams that are representative of race boats. One is 3/4 x 1" and the other is 5/8 x 1 1/4". The 5/8"wide one has 4% more cross-sectional area(re weight/length) but for that very slight increase in weight, it has 62% more stiffness.

A common size for stringers is 3/4 x 3/4". A simple change to 5/8 x 7/8" gives a 4% decrease in weight but with a 32% increase in stiffness. Go to a 1/2 x 1" stringer and get an 11% decrease in weight and a 61% increase in stiffness. For the same weight as the 3/4 x 3/4' stringer, you could go to a 9/16 x 1" stringer and get a 80% increase in stiffness.

Of course narrower stringers make it more difficult to fasten plywood, giving less area for glue and fasteners so there are some practical limits.

[bill boyes]

Interesting stuff. I have really had far better luck quality wise with cedar then I have with spruce. What glueing systems are people using? the last few boats I have built I have used Weldwood 2 part glue....decks are fastened with Tap plastics epoxy. The Weldwood seems to work better then epoxy in colder and or damper conditions. Daveracer

I use System 3. I have a pump with a heater for when it is cold. Like this A.M. 22 degrees in Yuba City. System 3 also has some new stuff out. They are located in Seattle. Check their Web Site.

[nbranews]

Nice Work

Look nice Keith. Be sure to take care of it. I think your daughter will be wanting to drive it in a few years.

[kampenracing]

Almost Done

Or B&H kit DMH is almost done!!!! Can't wait to drive it!!!!

[daveracerdsh]

Boats

Interesting stuff. I have really had far better luck quality wise with cedar then I have with spruce. What glueing systems are people using? the last few boats I have built I have used Weldwood 2 part glue....decks are fastened with Tap plastics epoxy. The Weldwood seems to work better then epoxy in colder and or damper conditions. Daveracer

[Mike Beegle]

Public lumber

t I There is also a place in Detroit or around there that is an importer bucould never get them to return my calls or price a skid.

Regards,[/quote]
That place is about 25 miles from the house... That place sucks... I would drive or have shipped to not have to deal with that place.... Dont buy any sitka from them they had a truck of it sit out side all summer in the weather and just before fall they sawed it up in 1x pieces...

Not friendly People at all..