Bottom "blueprint"

[wagspe208]

OK, I hate that term becaue I am an engine guy and it means S...
So, when you guys are dong all this work, do you do any bottom work? Sharpen edges, widen strakes (or whatever they are called), check for hook, etc?
How about after doing stringers. I'd find it hard to believe nothing moves during that process. Maybe not.
Thanks
Steve

[mrfixxall]

OK, I hate that term becaue I am an engine guy and it means S...
So, when you guys are dong all this work, do you do any bottom work? Sharpen edges, widen strakes (or whatever they are called), check for hook, etc?
How about after doing stringers. I'd find it hard to believe nothing moves during that process. Maybe not.
Thanks
Steve


i took some of mine out but left just enough,i left everything else alone..

[gcarter]

I've done a couple, one right side up; http://www.donzi.net/forums/showthread.php?t=43778

And one upside down;
http://www.donzi.net/forums/showthread.php?t=50476&page=20

The Minx was very successful, and pretty easy to do.

The TR was worse in its own way and took significantly more work.

Good luck!

[farmer tx]

I had the bottom of the Hornet III done, but don't have it rigged yet. Here are a couple of shots.

[MOP]

Sharpening the trailing edge of the transom is an old trick that many outboard racers do, it is also squaring off the trailing edge of the keel is very popular with sail boaters. Sharpening the area by the trim tabs will keep them cleaner at speeds, the rounded edge allows the water to come up.

This is a cut and paste from one of the racing sites I go to!

Hulls used in racing are typically blueprinted. That is, they’re turned upside down and the running surface is modified for more speed and quicker acceleration. Typically, this involves straightening the flat surfaces from the transom to about 6 feet forward, and sharpening all the pad, transom-to-bottom and strake edges. A flat, straight hull and pad will accelerate quicker and run faster, and sharp (literally almost cut-your-finger sharp) edges will shed water more easily than even slightly rounded edges. The combination of straightening and sharpening can result in substantial speed gains and may result in reductions in elapsed time, because the boat now “cleans up” more quickly and gets onto its pad more efficiently. We’ve seen 5 to 7 mph speed gains on production hulls, even those that only top out in the 60- to 70-mph range. Only a couple of days ago I recommended this to another member!

[mattyboy]

FarmerTx,

nice shots looks totally different from my hornet bottom
boat looks great

looks like they lengthened the inner strakes just like they did on the 18 when they stretched the 16 design. my inner strakes end around 4 feet from the transom so they did the same when the hornet grew in length

[farmer tx]

FarmerTx,

nice shots looks totally different from my hornet bottom
boat looks great

looks like they lengthened the inner strakes just like they did on the 18 when they stretched the 16 design. my inner strakes end around 4 feet from the transom so they did the same when the hornet grew in length


Thanks matty, Since he had the hull turned over anyway I had him go ahead and massage the bottom.

[Walt. H.]

OK, I hate that term becaue I am an engine guy and it means S...
So, when you guys are dong all this work, do you do any bottom work? Sharpen edges, widen strakes (or whatever they are called), check for hook, etc?
How about after doing stringers. I'd find it hard to believe nothing moves during that process. Maybe not.
Thanks
Steve
Yes you better have your bottom straight and where you want it before you glass in your new stringers, other wise it will hold the shape where it is if it has sagged due to not being properly supported while your old stringers were out.
Check with a long aluminum straight edge or even a 6ft florescent light bulb tube to use as a straight edge, then jack and block as necessary to achieve proper alignment, then you'll be good to go installing your new stringers knowing it'll be sag and or concave free aka hook and or rocker.

[wagspe208]

These pieces do not seem to have lifting strakes very low (towards the keel). Has anyone added a set in between the existing ones and the keel?
Right now, the shaft is 9 degrees. That is a lot of angle. I assume it is so steep to generate lift. If strakes were added, they would generate lift, and the shaft angle could be brought down a degree or 1.5 deg. This would add speed without having to add power. The only other question is would the strakes more toward the keel compound the crappy turning issue?

I bet everyone thinks I'm crazy.


PS.. would this kill the value of the boat any to make these mods? No one would really see them... most would never notice the changes.

[gcarter]

Help us out here!
What boat is this?

[wagspe208]

Oh, DUH!
I thought it was in an earlier post.
68 18' barelback v-drive. 350 chevy casale drive.
Deck coming off for what else. Engine has to go on a 100# + diet (cast intake, circulating pump, raw water pump, etc)
Thanks
Wags

[gcarter]

A couple of years ago Rootsy posted an explanation of why boats
w/the shorter inner strakes perform better than full length inner strakes. Look it up, it's very enlightening.
I wouldn't enlarge or modify them other than shortening the inner strakes.
As far as changing the angle of the shaft, here's a couple of pictures of
Sonny Levy's "28" that never did perform very well, Apparently it simply couldn't even begin to use the 1,000-1,200 HP it had available.
One of the things tried was to lessen the shaft angle that emerged from the bottom of the transom and the rudder was mounted further outboard and off the center line.
Anyway, here you can see the before and after pictures;

http://www.donzi.net/forums/attachment.php?attachmentid=46153&d=1242912449

http://www.donzi.net/forums/attachment.php?attachmentid=46154&d=1242912449

[wagspe208]

GCarter....
Hmmm...
I am asking... not doubting.. we are out of my realm of experience. I am a drag hydro guy so I probably will ask foolish questions.
This boat has 2 lifting strakes (or 3 if you count the ones at the vertical sides of the hull) per side. (I'm sure you know the bottom better than I do) It was suggested to me (by a HP boat guy but not a Donzi guy) that adding strakes between the keel and the existing inner strakes will help with lift. He said to start them at the front and terminate them about 3' before the transom (so you guys agree on not having full length strakes). He then said to lower the shaft angle 1 to 1.5 degrees. So, my strakes are lifting instead of my propshaft angle. And my flatter shaft angle is doing more pushing forward than upward.
It seems to make sense.... but as I have learned long ago... just because something works on paper does not mean it really works.
Wags

[wagspe208]

OH, BTW... losing weight in the back of the boat will also help with transom lift.
Wags

[gcarter]

GCarter....
Hmmm...
I am asking... not doubting.. we are out of my realm of experience. I am a drag hydro guy so I probably will ask foolish questions.
This boat has 2 lifting strakes (or 3 if you count the ones at the vertical sides of the hull) per side. (I'm sure you know the bottom better than I do) It was suggested to me (by a HP boat guy but not a Donzi guy) that adding strakes between the keel and the existing inner strakes will help with lift. He said to start them at the front and terminate them about 3' before the transom (so you guys agree on not having full length strakes). He then said to lower the shaft angle 1 to 1.5 degrees. So, my strakes are lifting instead of my propshaft angle. And my flatter shaft angle is doing more pushing forward than upward.
It seems to make sense.... but as I have learned long ago... just because something works on paper does not mean it really works.
Wags

That's a legitimate argument, I think.
On quite a few of the older deep V boats,
you would see additional strakes in the bow area....just 20-40% of hull length.
They probably do a very good job of giving additional bow lift.
Full length strakes give too much stern lift and handling generally suffers.
But lowering the shaft angle will vector thrust more in the plane of motion.....
and it could be almost like an Arneson using a surface prop.
I personally like that idea and would be a worthy undertaking.

[wagspe208]

That's a legitimate argument, I think.
Full length strakes give too much stern lift and handling generally suffers.
But lowering the shaft angle will vector thrust more in the plane of motion.....
I personally like that idea and would be a worthy undertaking.

So the issue with the full length strakes is transom lift... I assume it tends to rock the boat back and forth... like the Allison outboards I see at the drag races?

If I stop 3' back from the transom... I guess worst case scenario is I have to start cutting the strakes forward if I have to much lift?

Big ?... What would you use to "make" the strakes. If I just use glass it will take a while of building. If I make a wood strake and glass over it... well, you know the possiblility there.

Thanks
Wags

[gcarter]

I think the only place you could add strakes would be centered between the existing strakes.
Size, I wouldn't vary from the existing strakes. At least I've never seen multiple sized stakes on a hull. You may find there's not sufficient room for additional strakes.
Construction, I'll try to remember to scan some additional pages showing wood strakes. Anything you use will be a lot of work because once you reach the hull "rocker" at about station 6 or 7, the geometry will be constantly changing as the deadrise angle is constantly increasing moving forward.
I can think of a number of ways to build the strakes, but I would try to cut some short sections out of foam or soft wood and see how they appear......
You will have to determine all the unknowns as this is uncharted territory on these hulls.

[wagspe208]

I think the only place you could add strakes would be centered between the existing strakes.
I AGREE HERE.
Size, I wouldn't vary from the existing strakes. At least I've never seen multiple sized stakes on a hull. You may find there's not sufficient room for additional strakes. I AGREE HERE
Construction, I'll try to remember to scan some additional pages showing wood strakes. Anything you use will be a lot of work because once you reach the hull "rocker" at about station 6 or 7, the geometry will be constantly changing as the deadrise angle is constantly increasing moving forward.
I can think of a number of ways to build the strakes, but I would try to cut some short sections out of foam or soft wood and see how they appear......
You will have to determine all the unknowns as this is uncharted territory on these hulls.
THAT WAS WHAT I WAS WONDERING ALSO
Thanks for the information.
Wags

[wagspe208]

Here are a couple of pics of my last project.. a before and after.
What you think?
Wags
I think she turned out pretty good.

[gcarter]

That's pretty interesting.
Do you have any pictures of the drive end of it?

[wagspe208]

That's pretty interesting.
Do you have any pictures of the drive end of it?
Sure... here you go.
Wags

A couple before disassembly and paint. The last shot shows engine, clutch, v-drive. The first sort of shows back. Rudder is not mounted for towing.

[wagspe208]

Nope... if you see the back of the engine (facing front of the boat) there is a silver thing attached to engine (clutch) and just in front of that about 16" is the top of the v-drive. (behind the seat)
I know hydros.. not v-bottoms. You know v-bottoms. We are on the same page in different books. HAHA
Wags

[Ratliff240]

As far as lift and speed go i think your best bet would be a pad but i dont have any personal experience. Though i would like to. There is a picture somewhere on the registry of a 22 with one... i will try to search for it.

Also i found this on fountains website which is an interesting... its a sort of v shaped pad.

http://www.fountainpowerboats.com/sport/technology/hull.html

[gcarter]

I agree, that if you do anything, a pad wouold be the way to go.
But even that subject has lots of options.....
Some stand proud pf the bottom....
And others cut the round keel off!
That form really scares me as you're essentially cutting the hull in two halves to do that.
There's a lot to this subject (pads), and I don't know anyone qualified to do it except Chris Allard.

[wagspe208]

The pad is way out of my realm of knowledge. It is also much more work than I'd be interested in doing for a pleasure boat. Strakes, while not simple would not be bad to do. A pad would SUCK to do I think.
I may try the strakes. Worst case is I grind them back off. No big deal.
I am not usually a follow the crowd guy. Sometimes I am a hero, sometimes an idiot. LOL
I will sharpen edges (except the keel). Make the strut fit flush and nice (right now is is not what I consider nice... not even close). Change the shaft angle and see what happens. I actually make a new strut out of steel. I would be confident the power level will never be an issue then.
I am open for more ideas too.
Thanks
Wags

[gcarter]

Donzi Vee drives have never been particularly fast......for all the usual reasons.
For instance, the ultimate Donzi Vee drive would be WALO w/a blown big block Ford and about 900 HP does about 85. It's a beautiful boat and money was never an obsticle to going faster.
I think it would be insteresting to reduce the shaft angle similar to the drawings above w/the shaft exiting just in front of the transom.
I think speeds similar to outdrives would be attainable.

[Ratliff240]

I don't know anything about v drives so i will stay out of that but i think it might actually be easier to make a pad than extending strakes. Take a look at this 22

Looks fast to me :)

Sorry for posting these pictures because they are not mine but they exist somewhere on the site. My computer makes me download every picture i look at so I just found it in my temporary download file... here is the keel

file:///C:/Users/Ratliff240/Downloads/donzi%20pad%20keel%201.jpg

[wagspe208]

I don't know anything about v drives so i will stay out of that but i think it might actually be easier to make a pad than extending strakes. Take a look at this 22

Looks fast to me :)

Sorry for posting these pictures because they are not mine but they exist somewhere on the site. My computer makes me download every picture i look at so I just found it in my temporary download file... here is the keel

file:///C:/Users/Ratliff240/Downloads/donzi%20pad%20keel%201.jpg

I guess the "making of the pad" would not be horrible. The shape and size, design etc is way beyond me.
Oh, and I like drinking in my boat. If I want to go fast I jump in the hydro. I am just for a little more efficiency in what it is.
I would be intrested in seeing more pictures of a pad.
Thanks
Wags