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View Full Version : Strakes?? (DUMB CAN'T SPELL)



MOP
08-21-2002, 09:23 PM
Has anyone ever tried continuing the two inner strakes on a 16 to the transom? My thinking is it would help level out and lift the whole boat. I have been studying Atr's 28 Smuggler and looking at the running pic's on the Smuggler site. Another thing is back a few years I helped install Volvo speed rails they did improve speed and did lift the boat. All input always appreciated.

HP 600SC
08-21-2002, 09:38 PM
I beleive you meen strakes.....unless you got a big Porterhouse with my name on it!

Bad-Tat
08-21-2002, 09:43 PM
MOP,
Ask Forest about the strakes. The older 16's had strakes all the way back and his rides pretty high up. Especially around 65 mph!!!

Rodger
08-21-2002, 09:48 PM
It's difficult to predict the result. It probably would create more lift but at high speeds you'd think it would get more squirrely. But if you've ever looked at the Chris Craft 22' Stingers made in the mid 80's; they have full length double strakes and are absolutly fantastic handling boats at high speed in rough water. Much much better in the rough stuff than my 22' Donzi.

Rodger
08-21-2002, 09:55 PM
On my "66" 16'Donzi the inner strakes stop almost 6' before the transom.

Greg K
08-21-2002, 10:13 PM
Jamie Root and I have discussed this as well..I think he is the one that is going to do the testing. I think some pieces of aluminum or something will be epoxied on to test with. I'm sure he'll chime in on this one.

He told me that it's possible the old design just carried over because of lack of trim on the drives and also the power they had back then for the 16's. Another is that the small power plants could not get it up with full length strakes.

FWIW

MOP
08-21-2002, 10:29 PM
Me thinks the strakes lift would aid a lesser engined boat to plane :)

Formula Jr
08-21-2002, 11:29 PM
On the Stingers, just look at the Beam as compared to LOA. And I doubt the Stingers are 24 Deadrise. Now we come to what will be read as Heresy: 16s and 18s are outdated designs. Even Wynne in his later comments said the true deep vee (as opposed to a Delta Conic hull) was outdated. A really fast earily Donzi is not depending on its original design to go fast, its depending on all manner of added methods that circumvent the problems a skinny, heavy, 24 degree deadrise has at plus 60 speeds. You can put wings on the drive skeg, Add huge trim tabs, cut in pads, Raise the X, use surface props, fair out the hook, add rocker and all that. What you end up with at speed is a machine that simply isn't dependent anymore of being a Donzi cause you're not even using the hull as a wetted surface. Hunt was the one that designed the lower strakes to terminate before the transom. This was the whole point to his patent on the "Flooding Keel" meant to reduce lift and define the running angle of the bow. Aronow insisted on running the lower strakes all the way to the transom which was later regarded as a mistake and later Donzis had a radiused flooding keel. If you do run the strakes all the way back , you end up with a very flat running boat that would be compensated by drive trim, which makes the boat squirrly, which would then be compensated by massive trim tabs. So once your on this path, you don't even have to think in terms of a Donzi hull, you're just looking at the flight characteristics of the drive, trim and occassionally the last 4 inches of the keel. At this point we are also not talking about an offshore boat cause theres only a few sea states you can run this way. In quartering or parallel seas you can't use all this stuff anyway as the boat will still be to unstable to correct unless you throttle back to where the boat is back in the water and using the stablity of the mid-ship and forward topside strakes.

oldLenny
08-22-2002, 12:12 AM
I'm gonna have the same problem as well judging by this pic. (strakes)

http://www.donzi.net/photos/ACF4B2.jpg

Does this help us find out the year?. We know pre 70 but not when as there is no ID...

Formula Jr
08-22-2002, 12:26 AM
Why is everyone telling me to get a point? :D

Looks '66 to '68.

http://www.donzi.net/dlist/skisporter/ii.htm

Greg K
08-22-2002, 12:28 AM
Owen..so you're saying leave well enough alone?

On another subject...which was about left hand drives...or the invention of the stern drive..this page is interesting in regards to the Stern Drive Invention (http://www.rbbi.com/folders/pat/isd.htm)

And found this which has had some controversy of late I think Hull design (http://www.compsportswi.com/regal/fastrac.html) Something about Duo Delta Conic Hull (http://www.rbbi.com/folders/pat/regal/regal.htm)

Formula Jr
08-22-2002, 01:31 AM
Not so much, "leave well enough alone." The things you can add now are fantastic. The main point I'm making, if I can distill it, is - Like the 90MPH 16 posted recently here, once you are on this path of speed, as opposed to seaworthyness, the plan of action is pretty clear cut. The hull is meaningless and there's no point in altering it. Its all just HP, drag and lift characteristics of the drive, and what happens after the transom is what really counts. The boat will still work well at 40/50 MPH with out messing with the hull, but above and beyond that , you will only be able to use the "additions" under a very small set of running conditions in a semi-safe manner. And I'm really making a safety issue out of this, cause all that stuff isn't really going to let you run any faster than you can under certain conditions, and no one should ever think that just because they made the boat go faster using these methods under one condition, that they can now go faster in all situations. And if you know what your doing, tabs and trim can make a boat more STABLE in all conditions but not Faster. The opposite is also true, you can make the boat more unstable and faster. The after market lifting strake additions MOP was talking about are well known as Corrective Devices for badly underpowered and badly designed boats, usually larger than 16's or 18's. For this, they work well and have a place.

But there's no point in adding them to a newer radiused keel if the intent is flat water top speed. It would be easier to just cut a pad and ultimately there's no point to owning a Donzi if you just want flatwater top speed.

MOP
08-22-2002, 06:37 AM
Ok what I was thinking was that I might be able to get a better ride in the chop at maybe another five miles an hour, looks like maybe not. Top speed to me is not as important as running faster in a chop, I guess I will keep mushing through it.

Rootsy
08-22-2002, 07:59 AM
My thoughts on the inner strake extension isn't go go all of the way aft like the early 18's. As long as i run a cleaver i don't get as much bow lift and it is controllable into the upper 60's unless in a cross chop and it wants to flip flop back and forth.. hit it head on or quartering and you are fine. This all has more to do with prop torque or the lack there-of.

I have been pondering the ride characharistics between the 16 and 18 all summer. Noting the differences in design and ride. a few of the more obvious differences the 18 has vs the 16 are: lack of hook which does nothing at speed, inner strake termination 4 feet more aft (2 feet vs 6) and flatness of ride and increased speed with the same hp vs a 16. the extra foot and a half of length is right in the running surface in front of the motor to the rear seat area. moving the CG forward helping to hold the boat level.

My theory is NOT to extend the inner's all of the way to the stern. I think this would cause WAY too much lift on the hull and it'd ride tooo high. My purpose for experimentation will be to find a bit better ride attitude and some stability at higher speeds under varying conditions. Thoughts are to gradually extend the inners, maybe a foot at a time in a temporary manner until the best combinations of speed and stability and ride charactaristics are obtained. This may be 1 foot it may be 3 feet i do not know quite yet. But the 16 being shorter there is less weight fore in the boat so the boat rides really bow High, figure i will experiment with some lead shot in the nose. there is less strake for it to ride on to level it out so it rides as a wedge through the water on a smooth rounded surface, these two combos are some of what i am trying to decrease. i think the snowplow effect scrubs off some speed... as well as burying the sterndrive causing more drag... if you can level it out and lift the stern and give the boat something flat to ride on a bit you might get the prop a bit higher and get some more speed out of it plus reduce the effect of torque on the hull from the prop.

to further strengthen some of my points... when i have a full tank of fuel... my boat rides flatter and i pick up about 1/2 mph.

I really don;t think that the 16 will ever be as rock solid as the 18 but it can be better than it is. The 18 tends to ride very flat with not much bowlift but it does get on top of the water and go and it is rock solid in feeling, yet it only weighs a few hundred lbs more than a 16.

whether any of this will work like theorized or not is yet to be seen but when i do get to it i am sure everyone will be privy to my data and results... right now... 14 1/2 x 23 cleaver, 320 or so propshaft HP, 1.5:1 alpha Gen II, 2600 lbs with fuel and me.. 66 1/2 mph and a slight handful but nothing tooo terrible.

and owen, your history lessons on who what and why intrique me... keep it coming... nothing like background to build off of!!!!

FlatRacer, aka BarrelBack
08-22-2002, 09:12 AM
All this theorizing and tinkering is great stuff. There is one thing that we should remember though. All vehicles are designed to perform within a specific speed range. A performance "envelope", if you will. No vehicle can do everything well.
Case in point: I had decided that I wasn't getting enough use out of my raceboat, so since it only takes a couple hours to change the engine, I built a mild 396 to toss in it for lake running and waterskiing.
So, I'm out on the lake one morning, pounding around, getting beat to hell. I've got my left foot burried in the plate to keep it level. The hull's sticking to the water, hunting and wandering, just wouldn't break free. Every cruiser wake was a jolt up my spine. At WOT, the hull still wanted more horsepower. In these boats there is that certain sweet spot where the handling comes together and it just dances, quivering through the turns and bumble beeing up the straights, constantly making tiny course corrections as the prop furiously claws at the water for more thrust. (I think I need a cigarette eek! ) Unfortunately, the sweet spot starts at about 80 mph, and this motor was only getting me to around 75, so the ride was just a miserable tease.
Later that day, a guy cruised by in a 18' Donzi V-drive, so I asked him for a ride. That boat handled so sweetly at human-type cruising speeds, the deep V bottom gushing softly through waves that would've hurt in the flat. Such a nice ride that I was actually jealous! The memory of that ride on that day is why I'm looking for a vintage 18' now.
I yanked that 396 out of the raceboat and sold it that year.
I learned my lesson that day. You can't successfully make a pleasure boat into a raceboat, or conversely, a raceboat into a pleasure boat. They're just not designed to operate within those parameters.
I guess my point is this: By all means, go ahead and upgrade you motor, drives, props etc. to extract every last ounce of performance you can get out of your boat. Just don't waste too much time, energy and money trying to turn it into something it's not. I think you should enjoy your Donzis for what they are: the coolest looking, meanest sounding, most tastefully styled sportboats on the water.

IMHO,
Eric :)

ALLAN BROWN
08-22-2002, 09:34 AM
A couple of things....

Many of my peers say that strakes were attached to vee bottoms to keep the Cubans from sliding off while they sanded the plug.

The inner strakes were shortened to let the bow rise, and to prevent aeration of the propellor in hard turns.

I have filled all the strakes in the 16' Donzi mold, and built a smooth bottom. Didn't make a damn bit of difference....

ToonaFish
08-22-2002, 01:13 PM
Well, Brownie, that explains it... as the rafts from Cuba became smaller to avoid detection, the refugees were of necessity smaller in stature, thus the strakes became smaller! So tell me, the design of the clamshell vents, were they influenced by actual Cuban clams from the Bay of Pigs? :D

Bunches,

Celene 'thinking that one of Brownie's chapters should be on how Donzi influenced all world events'

GEOO
08-22-2002, 01:24 PM
The strakes give lift to the hull. By adding larger or more strakes to the rear of the boat you will lift the rear more and tend to lower the bow. This is a good thing at slower speeds, the rear of the boat weighs more. The faster you go, the less lift you need built in to the hull; the rear of the boat is wider with less of a deep vee which creates alot more lift then the bow at higher speeds. You need a good balance of lift to keep the boat at the sweet spot. The sweet spot is when you have less wetted surface but don't have the bow real light so the boat get's flighty or porposes.
I have found the best way to ride in a 1 to 2 foot chop is to raise the trim to air the boat out a little then to put the trim tabs down level or just below 1/8" down from level, to keep the bow in shape. You'll be able to feel the bow lift when you hit a wave then the tabs build pressure and leave the boat back down. It's a neat feeling skipping across the top of a small chop.
Also the more power you have, the faster you can run in choppy water. You don't need to air the boat out as much to obtain the speed.

oldLenny
08-22-2002, 07:47 PM
With all this input, theories, actuals and such it is obvious that this hull is going to be interesting... It is YOUR X-18 (CLASSIC)hull with a pad and 'printed'.

http://www.donzi.net/photos/xhull18.jpg

http://www.donzi.net/photos/pad.jpg

http://www.donzi.net/photos/pad1.jpg

Definately, the "Bench X-18" is going to be "fun".

P.S. The pad is LEVEL and TRUE with the entire length of the keel. Bottom was blue-printed, and the slight rocker on the ORIGINAL was removed. The pad is added TO the hull bottom to fill in the slight rocker as it was NOT carved out of the existing radius in the keel. It measures 9 1/2" wide and starts about 52" forward of the transom in its "humble beginnings". It starts with the same existing forward radius built in and ends up flat (horizontal) at the stern. More pics will follow soon. (the interesting ones) :rolleyes:

Rootsy
08-22-2002, 08:04 PM
Lenny,

you have / made a mold for an X-18 hull????? eek! MAN, where have I BEEN :confused:

HyperDonzi
08-22-2002, 09:47 PM
M.O.P. it had to come sometime, until now your post were flawless, but simple spelling mistakes....

hahahahaha. you still know a lot about everything with one spelling error.

oldLenny
08-23-2002, 03:34 PM
Jamie,..."yep"

Kent Perroux
08-23-2002, 03:38 PM
Extending Strakes on the Classic?

Hmm did that.

1) Not recommended to go all the way back to the transom on the rounded keel. That was my first shot. Great take-off; but:
a) can't get the bow to lift
b) can get tossed out during a hard turn. (how do I know this? Ask my son.)

2) went back home and cut 6" of the strakes. Still that way today.

Takes some getting used to and I might have to modify when I get the Bravo drive change completed. Were there advantages? Yes, I picked up a couple mph and better high speed running in moderate chop. Lands much harder if you like to jump wakes and will increase the probability of a stuff.

Personnally I like the extended strakes the way I have them now. The boat planes faster, rides higher and has better control at the speeds I was running (55-65). When running in the ocean, you have to be a lot more careful, but if you get your timing right, you can run faster because you don't drop as much between the waves. If you strew up though....better have you lifeline on.

Kent

Forrest
08-23-2002, 04:00 PM
Lenny, what are you guys doin' up there? So that's an 18 hull mold with a pad. Hmmmmm . . . When are you guys going to knock one out? Do you have a deck mold or is the plan to use an existing C18 or X-18 deck?

Inquiring minds want to know!

oldLenny
08-23-2002, 05:28 PM
Forrest, you "guys" is guy, me... :rolleyes: Yes, I have all the parts for your standard X boat. (4 pieces) I am not making ANY that way and am not cloning real ones. They are "Bench Boats" http://www.donzi.net/photos/osaffell030.jpg , all of them. This is old stuff. I have been doing this for about a year and a half and "blabbing" about it from time to time for about as long. :rolleyes:

When am I going to "knock" the first one out?... is not the question. I have 4 hulls done and the decks,...well,...they're close. Pic's soon. These are not expensive boats to do (about $2400 US each, c/w all the boat glass parts (hull, deck, liner/tub, forward area) but w/o labour or any compensation for the years off of my life,...These are "HIGH END lay-ups, "Bi-axle and core matt etc..." vac bagging is in the future, hence the "lip" on the hull for sealant and a bladder.

...and I want to try a number of things on them, get 'em right and then pass a couple on to "somebody" to play with.

Scots' boat is going to get done first as I am MORE interested in it...

smoothie
08-24-2002, 11:37 AM
Lenny,Im impressed,a bench seat X-18,what more could you ask for!and you made the whole boat with your own hands,Man the talent,skills and knowledge thats on this website is never ending,Why with all that is here we should all pitch in alittle $$$ and make a Donzi.net boat,kinda like what Hot Rod mag does with cars :D

oldLenny
08-24-2002, 12:08 PM
Smoothie, you give me too much credit. The shape I owe to the likes of Don, Walt and Jim. I just changed the cockpit a bit(Chisholme gets the credit for the original concept) and I added the pad idea...



The X-18 was styled by a Detroit bunch, with putty and stuff. Strictly a deck redo. The late Tim Chisholm, Chairman of Donzi at the time, also hired a new PR firm. One of the slogans..."When they built this baby, they threw away the mold!".

BROWNIE This isn't "tuff" stuff when someone else gets you "going".

...I wish I had the talent those guys did...

Formula Jr
08-24-2002, 02:20 PM
What am I doing? Collecting all these clapped out boats, when I should be saving up for a brand new LENZI 18!!!! :D

350 Mag
Fresh Water Cooling
Bravo III
18 inch K-planes
50 gallon belly tank
Popup cleats
Stainless rub rail
Stainless Marine Exhaust
Morse Controls
Momo wheel
Bilt-Rite Custom Interior......

:)