Notched Transom...Pad mods....?????

[SilverBack]

Ok...George, Lenny and Michael..... and anyone else that is a hull expert.....


I hope this goes better than the last one and it is even crazier...but....


Can you notch your transom after the boat is built and rigged???? I am looking at bow lift and clean water and thinking ....


I took a bunch of weight out of the back of my boat. Cast iron manifolds...cast iron heads....a bunch of un-needed stuff. I bet it was at least 300 lbs. I am having trouble with getting the bow up. I was thinking in terms of a lever it would make it much easier if the pivot point was moved forward a foot or so. I was also wondering if there was any way to modify the pad to be more like a velocity pad. Wider in the rear.

Rick at IMCO suggested cutting the last 4 feet of the lifting strakes off. But I think at 90 they are out of the water anyway. How much stern lift would you get from the splash hitting the last 4 feet of strake?

You guys know where I am with things...What is doable???

[SilverBack]

Mark boos has driven the boat and has some more props that he is going to try. I am sure that he will get it better. I am going to let him take care of it but I do like to know what you can do and what is not possible.

What is possible and what is not possible. What do you think the changes would tend to do? That kind of thing. There was a guy over on speed wake and he did some of this stuff ..he had trouble but it worked out good in the end.

[SilverBack]

You just will not let me have any fun talking about hacking up my hull......killjoy!!!!:wink:

[Last Real Texan]

Some good info here...I think it turned into a train wreck in the end but not really sure

http://www.speedwake.com/upload/showthread.php?s=&threadid=44194&highlight=no+bow+lift


Tex

[BUIZILLA]

I am having trouble with getting the bow up. I was thinking in terms of a lever it would make it much easier if the pivot point was moved forward a foot or so. and if you don't change the CG along with it??.... :wink: if you really, really, really want to pursue this fantasy, I highly suggest you change hulls... there HAS to be a reason why the vast majority of hull builders don't do this... a 260 Velocity comparison comes to mind...

Have you even considered how, with the route you've taken, it would handle and respond, at say, cruising speeds? where you spend 99.999999999% of the time anyways... and where your WIFE and family would enjoy your company and the boating theme?

[gcarter]

I agree w/Poodle.......learn to drive your boat.
If it were me, before I started butchering the bottom of the hull, I think I'd extend the pad below the bottom of the hull. I've limited experience, but I've never seen a pad like yours.
If it were me, I'd be a lot happier with it extending 1/2"-3/4" below the bottom with sharp vertical sides.
Thiis modification would be much easier to make and not modify the hull integrity.
The amount of weight you've taken out is really diddly and a small percentage of the total.
You'd do better off gutting the enterior.
All of this is just my opinion.
What you do is your own business.
But in the end, I think you'll be happier to take a step at a time.

[Ed Donnelly]

Anything is possible, but, this step is way down the road, as you have more horsepower, bigger tabs, prop testing to try out first........Ed

P.S. A really good pic of the bottom, search biggest engine in a 16 c 08-02-2007 post # 8

[zelatore]

I also wonder exactly how much weight you lost - maybe not as much as you would first think. Yeah, you dropped a ton loosing the cast iron stock exhaust, but then you added some back with the blower and it's parts.

What's the shipping weight on that big 'ol box from Procharger? 100 lbs?

[osur866]

And the dual ram steering and all their parts, I lost 83 lbs with my exhaust and added most of it back with just the dual ram steering. Steve

[gcarter]

[quote=gcarter;485620]I agree w/Poodle.......learn to drive your boat.
If it were me, before I started butchering the bottom of the hull, I think I'd extend the pad below the bottom of the hull. I've limited experience, but I've never seen a pad like yours.
If it were me, I'd be a lot happier with it extending 1/2"-3/4" below the bottom with sharp vertical sides.
Thiis modification would be much easier to make and not modify the hull integrity.quote]

If you think about it, this mod would also raise your "X" by the same amount.

[BigGrizzly]

Well Keith, I also know where Mark and Rick came from and their boat preferences are. First of with Mark it can always be better. The props he is going to try will not be the same that I will use. I am also sure he did not use the 30 I sent you and given it a chance. That 6 blade is a waste. You don't want to hack that boat up. Forget the notch thing on that hull. You have got a PAD. All the issues will be centered around it. Your boat is different then any most people have worked on. I will tell you this, The boat needs to be tailored around you.:yes::eek: Not Mark, Not Rick and not ME, but YOU!!!! It is like You someone recommending that that 6 blade.:frown: What works down at Mark's might work up here. Little things like slouching in the seat change things at 80 mph. A 230 pound driver that is 6'2" verses a 230 pound driver that is 5'6". Even a marine engineer can't tell you what will happen. Like props, it is called testing.

[mjw930]

and if you don't change the CG along with it??.... :wink: if you really, really, really want to pursue this fantasy, I highly suggest you change hulls... there HAS to be a reason why the vast majority of hull builders don't do this... a 260 Velocity comparison comes to mind...
Buiz,

What issues regarding the 260 are you talking about? (BTW, I was in Steve's shop when he blocked the 280 (26') mold to create the 260 (24') plug) and I agree, it is not one of his best efforts).

SB,

I think you have it backwards, your standoff box is the defacto solution to adding additional leverage to carry the bow. The idea is to move the prop farther from the fulcrum point thus increasing leverage. Notches are ther primarilly to allow for a higher X, not to effect leverage. The notch is designed to move the exit point of the water from the pad further from the prop. Since the water moves up and back you can raise the X dimension and still keep the prop in the water. Moving the drive back onto the transom and notching the pad won't have the effect you are looking for. Remember, props don't actually lift the bow, they exert upward (stern lifting) or downward (bow lifting) force on the transom. Consider the bottom a see saw with the CG being the middle. The further back you move the prop the less force it takes to pivot the bottom on the fulcrum.

Look at the picture and compare this bottom to yours. One thing you should notice is the fully extended strakes and reverse chine. These provide lift and, because they are outboard of the center line they assist in controlling the boat (keeping it level and on the pad). Even with all that this boat must be driven meaning you are constantly inputting minor corrections to balance the boat on the pad, something that round keel or V keel boaters are not familiar with. At anything over 80 mph the corrections need to be part of your muscle memory or you will not have a pleasant ride but it takes 30% less power to attain those speeds :).

Case in point, this boat with a 26' center line, 5500 lbs wet and 540 hp runs a consistent 83.5 mph on GPS...... What does a similar sized Donzi run with 540 hp, regardless of pad or ventilation?

[BigGrizzly]

That one I can answer. First lets change the parameters and make both superstructures the same. Lets take the 27 ZX. there were 2 up here one Tex now owns, the other had a 540 bulldog in it. when I fixed the darn tabs and Garry fixed the carb that came screwed up from Merc. It ran that good. He is still out there and owes me money. A 22 classic will always run faster then a 22ZX with the same power. The superstructure is better for the speed on the classic. Please don't anyone claim the 22 ZX is a faster Hull. I was told by the late Steve Simon that it was not. Plus I have never been beaten by one with the same HP even with a shorty on it.

[The Hedgehog]

Buiz,
What issues regarding the 260 are you talking about? (BTW, I was in Steve's shop when he blocked the 280 (26') mold to create the 260 (24') plug) and I agree, it is not one of his best efforts).
SB,
I think you have it backwards, your standoff box is the defacto solution to adding additional leverage to carry the bow. The idea is to move the prop farther from the fulcrum point thus increasing leverage. Notches are ther primarilly to allow for a higher X, not to effect leverage. The notch is designed to move the exit point of the water from the pad further from the prop. Since the water moves up and back you can raise the X dimension and still keep the prop in the water. Moving the drive back onto the transom and notching the pad won't have the effect you are looking for. Remember, props don't actually lift the bow, they exert upward (stern lifting) or downward (bow lifting) force on the transom. Consider the bottom a see saw with the CG being the middle. The further back you move the prop the less force it takes to pivot the bottom on the fulcrum.
Look at the picture and compare this bottom to yours. One thing you should notice is the fully extended strakes and reverse chine. These provide lift and, because they are outboard of the center line they assist in controlling the boat (keeping it level and on the pad). Even with all that this boat must be driven meaning you are constantly inputting minor corrections to balance the boat on the pad, something that round keel or V keel boaters are not familiar with. At anything over 80 mph the corrections need to be part of your muscle memory or you will not have a pleasant ride but it takes 30% less power to attain those speeds :).
Case in point, this boat with a 26' center line, 5500 lbs wet and 540 hp runs a consistent 83.5 mph on GPS...... What does a similar sized Donzi run with 540 hp, regardless of pad or ventilation?

They don't make a similar size Donzi that only weighs only 5,500 lbs.

[The Hedgehog]

That one I can answer. First lets change the parameters and make both superstructures the same. Lets take the 27 ZX. there were 2 up here one Tex now owns, the other had a 540 bulldog in it. when I fixed the darn tabs and Garry fixed the carb that came screwed up from Merc. It ran that good. He is still out there and owes me money. A 22 classic will always run faster then a 22ZX with the same power. The superstructure is better for the speed on the classic. Please don't anyone claim the 22 ZX is a faster Hull. I was told by the late Steve Simon that it was not. Plus I have never been beaten by one with the same HP even with a shorty on it.

What kind of speed did you guys get out of the 27ZX with the 540 Bulldog?

[BigGrizzly]

We got just shy of 85 after propping-finally, if I drove If the owner drove about 78. That was the real reason I was going to buy Tex's boat, befor it disapeared and he got it. Tex's boat was a dog befor it disappeared from RPM

[The Hedgehog]

We got just shy of 85 after propping-finally, if I drove If the owner drove about 78. That was the real reason I was going to buy Tex's boat, befor it disapeared and he got it. Tex's boat was a dog befor it disappeared from RPM

That's wild. I never know of your history with that boat.

[BUIZILLA]

Buiz, What issues regarding the 260 are you talking about? (BTW, I was in Steve's shop when he blocked the 280 (26') mold to create the 260 (24') plug) and I agree, it is not one of his best efforts).

Case in point, this boat with a 26' center line, 5500 lbs wet and 540 hp runs a consistent 83.5 mph on GPS...... What does a similar sized Donzi run with 540 hp, regardless of pad or ventilation? Mark... no issues at all... this is the comparison I was thinking, you just verbalized it :yes: there are some fassstttttttttt 280's and 260's out there with 100hp or more less power than it takes a 22C or 27ZX to be equal speeds... and the pads aren't flat either, they have a slight reversed radii arc... I am a HUGE fan of 22 Velocity outboards, especially the earlier kevlar hulls.. if I hadn't just paid 26k this week in real estate taxes i'd a bought that 22 Velocity OB for sale in the Carolina's...

[mjw930]

We got just shy of 85 after propping-finally, if I drove If the owner drove about 78. That was the real reason I was going to buy Tex's boat, befor it disapeared and he got it. Tex's boat was a dog befor it disappeared from RPM

What crank HP was that 540 bulldog running?

Here's (http://www.donzi.net/forums/showpost.php?p=437398&postcount=20)the post with the dyno from my old Velocity, HP for HP I'd put it up against ANY other v-bottom boat of similar length and for many years we did just that in APBA F1 class and won our fair share of races, championships and kilos. I don't recall any Donzi's in F1 class but I could be wrong........

[mjw930]

Mark... no issues at all... this is the comparison I was thinking, you just verbalized it :yes: there are some fassstttttttttt 280's and 260's out there with 100hp or more less power than it takes a 22C or 27ZX to be equal speeds... and the pads aren't flat either, they have a slight reversed radii arc... I am a HUGE fan of 22 Velocity outboards, especially the earlier kevlar hulls.. if I hadn't just paid 26k this week in real estate taxes i'd a bought that 22 Velocity OB for sale in the Carolina's...

Damn, there was a 22 OB on the market!!!! I absolutely love that boat.

Yep, if you look at the pad surface and profile along with the chine radius there are some interesting tweaks. Compare them to an Allison and you'll see a lot of similarities, so many that Darris and Steve were not on speaking terms for a while but Steve will always credit Darris Allison as his "inspiration" for the design .....

[SilverBack]

Mark and Jim...that is what I was talking about..I run lakes not big waves.....I run small lakes that are pretty smooth most of the time...I was saying the same thing as you guys...I know that the Velocity is a faster hull....my boat does not weigh any more that that boat. I was wondering if there were any improvements that I could make to get it to run more like the Velocity.


Jim,
I have made up my mind that if it did come down to changing hulls that I am going to a cat hull. BTW...my boat runs like it is on rails at 70 I will be sending most of the time at 70 or below..like 99.999999% so I can take my time if I want to....I don't live around any boat builder or modification places and just did not know the answer to ...what is possible and what will ruin your hull ...what will make your hull too week.....this is not a race to the finish line ......this is a hobby for me and I have been having fun working on it lately....I am learning about things that I never knew about before ....that is fun for me...boating is fun ...but this building project has been fun too....My main objective is not to get in the water as soon as possible and I can drive a bass boat a 100mph but it is not much fun..it is more like work to me....I am just trying to see what can and can't be done with the hull.....


Thanks guys for the help!!

[BigGrizzly]

The bull dog was suppose to have only 540. However a little work on the carb (it is really bad out of the crate)and some cam degree in, and most will match their cubes. This is not what is so good with that engine its the torque. That bore stroke works sp well. I have seen 700 and change with the same torque on 89 octane. If I had one I could park the RC special and bolt it in. If I did the only belt you night see on the engine would be the Alternator belt, but that will probably be driven by the flywheel. I saw one driven by the blower belt. At first I though it was an idler pulley..

[BigGrizzly]

I don't like cats they are touchy. I driven some fast ones but unless there really big Turning is no fun. As for the lake and calm, they call Lanier the ocean

[SilverBack]

hey...if you don't like cats I would recommend that you not get one!!! :wink:


The ones that I have been around go 10 to 15 MPH faster than a Donzi with the same power and they drive like they are on rails going straight....That is all that I want to do...... My Donzi is going to be fine though..if I can get a good prop for it and oh...yeahh what was that other thing on my checklist.....oh..yeah...learn how to drive!!!

[mjw930]

Mark and Jim...that is what I was talking about..I run lakes not big waves.....I run small lakes that are pretty smooth most of the time...I was saying the same thing as you guys...I know that the Velocity is a faster hull....my boat does not weigh any more that that boat. I was wondering if there were any improvements that I could make to get it to run more like the Velocity.


Jim,
I have made up my mind that if it did come down to changing hulls that I am going to a cat hull. BTW...my boat runs like it is on rails at 70 I will be sending most of the time at 70 or below..like 99.999999% so I can take my time if I want to....I don't live around any boat builder or modification places and just did not know the answer to ...what is possible and what will ruin your hull ...what will make your hull too week.....this is not a race to the finish line ......this is a hobby for me and I have been having fun working on it lately....I am learning about things that I never knew about before ....that is fun for me...boating is fun ...but this building project has been fun too....My main objective is not to get in the water as soon as possible and I can drive a bass boat a 100mph but it is not much fun..it is more like work to me....I am just trying to see what can and can't be done with the hull.....


Thanks guys for the help!!

I don't think bottom modifications are going to get you anything aside from headaches. With the stand off box and the right prop you've pretty much done all you can with that hull. The fact that it's "on rails" at 70 mph pretty much indicates that's the design speed of the hull. Any modifications to the hull could lead to disastrous effects unless you had a certified naval architect design the modifications for you.

BTW, I don't think tabs are going to make all that much difference at these speeds. Running an overly long tab could do some strange things at speed unless you can fully retract them from the water stream. I was just talking to one of the guys that used to work in the Velocity factory and he was telling me about a 22 they had in there to be dialed in by Steve. The owner had put a big motor and 380 K-Planes on it. The boat would run well into the 90's but whenever you got above 95 it would fall off the pad, almost like a high speed porpoise. If anyone can drive a 22 Velocity at speed it's Steve Stepp and even he was having problems. As luck would have it one of the tab pumps died so they removed the tab plates. When they took it back out the handling issues were gone. It turns out as the boat got all the way up on the pad and started packing a little air under the bow it would push the rear of the tab into the water stream which pushed the bow down. The boat would rise and fall to the point where it became seriously unstable. They cut 6" off the tabs and everything was fine.

[SilverBack]

I guess my next step is going to be putting trim and tabs switches on the throttle and trying to find the right prop..I bet the right prop will make all the difference...It has not had nearly the right prop on it yet ....not even in the ball park..I have been wondering about this hull stuff every since you posted a pic of that velocity on my 25 pad problem thread.......I have had a 6 blade that was labbed for extra stern lift for a cat and two 3 blade that were made for donzi classics and boats with the drive planted way deep!!!


I am sure with a high rake and higher cup in a 5 blade I will be ok!!

[SilverBack]

Plus..that guy over on speed wake really did pick up some performance modifying his hull....

[mjw930]

Plus..that guy over on speed wake really did pick up some performance modifying his hull....

His mod was simple, he reduced the lifting surface in the rear of the boat to effect the bow riding higher. If I recall you don't have full length inner strakes so his modification wouldn't help you. If you do have full length inner strakes then it might be a modification worth considering.

I looked for a picture of your hull but couldn't find one. Is one posted here?

[BlownCrewCab]

Keith, check this pic. Not saying you should cut your boat, but it can be done very succesfully. this is a Non stepped fountain, they cut the rear bottom off and moved it up 2" to create the step, Raced for years with it, even won the World champs in key west.

http://sports.webshots.com/photo/1034493063027650919AzLnak

[SilverBack]

His mod was simple, he reduced the lifting surface in the rear of the boat to effect the bow riding higher. If I recall you don't have full length inner strakes so his modification wouldn't help you. If you do have full length inner strakes then it might be a modification worth considering.

I looked for a picture of your hull but couldn't find one. Is one posted here?


Mine DO go all the way to the back!! And they are pretty close to the center of the boat!

[SilverBack]

BCC..is this what it looked like on the fountain??

[BlownCrewCab]

BCC..is this what it looked like on the fountain??


No, Not quite that fancy, they just made a simple step. Your pic has a step, a notch, and what looks like an after-thought (the center raised running surface that was probably just blocked up in the mold for some reason) adding the longitudinal steps is just making more surface area which is making more drag.

[SilverBack]

Michael,

How big of a job will I be looking at?? I have access to a body shop....Is that something that I could fly you and your wife down for the weekend and get done or would it take longer than that???

[BlownCrewCab]

Michael,

How big of a job will I be looking at?? I have access to a body shop....Is that something that I could fly you and your wife down for the weekend and get done or would it take longer than that???


Ha, No, Thats a Massive undertaking, Motor out, flip the boat over, No,No,No, I don't think you want to do what that would take. I/We love your enthusiasum (sp) But you probably have enough go fast tech & Goodies in your boat right now to achive your goals once you have it dialed in. Lets see what you can get with what you have, Then if for some reason you want to go faster we'll see whats holding you back, Boat, Motor, Prop, Balls, and we'll adjust accordingly. I'm sure theres some setup/combo just using what you already have without modifiing the hull that will please you. No, your not taking it apart, your just finally getting it together.

[SilverBack]

I wasn't talking about all of that stuff...just the lifting strakes!!! But ok.....

[BlownCrewCab]

I wasn't talking about all of that stuff...just the lifting strakes!!! But ok.....


Whew, Good, you scared me for a minute. (let me go let the dogs out BRB)

[SilverBack]

Ha, No, Thats a Massive undertaking, Motor out, flip the boat over, No,No,No, I don't think you want to do what that would take. I/We love your enthusiasum (sp) But you probably have enough go fast tech & Goodies in your boat right now to achive your goals once you have it dialed in. Lets see what you can get with what you have, Then if for some reason you want to go faster we'll see whats holding you back, Boat, Motor, Prop, Balls, and we'll adjust accordingly. I'm sure theres some setup/combo just using what you already have without modifiing the hull that will please you. No, your not taking it apart, your just finally getting it together.


I hope that it is not that one!!!



Well maybe we need to just find a lake and a weekend and you can give me driving lessons!!! I know that is my number one problem!!!!

[BlownCrewCab]

Okay, I'm back.... At the speed your planning to go I don't think modifing the strakes is going to do much. the faster you go the more pressure you have on the running surface. at those speeds removing the strakes isn't going to let it squat any more than if they where still there. the goal is to have enough leverage from the prop to carry the nose, and NOT to let the rear squat to get a better angle of attack. you want to get your angle of attack while going over the water not through it. someone mentioned earlier about a sea-saw, thats exactly right and the goal is to be running as high in the water as possible (less drag) and still have enough good prop bite to get positive trim to carry the nose while propelling the boat forward. there should be a prop out there to let you do it where your X is now, But it is possible you may have to go down an inch to get it, if thats what it takes to carry the nose it would be worth it cause then you know you have enough bite to get all your speed.

[SilverBack]

Good Deal...now we just need to do those driving lessons!!!:shocking:

I know that it is hard to think about when you are freezing in front of a fireplace up in TN but just try to remember your youth back in southern FL.....there are still people out boating this time of year!!!

[BlownCrewCab]

Good Deal...now we just need to do those driving lessons!!!:shocking:

I know that it is hard to think about when you are freezing in front of a fireplace up in TN but just try to remember your youth back in southern FL.....there are still people out boating this time of year!!!


ah yeah, The Lucky ones:yes:.. I sure miss tropics, everything about it, sunshine, fishing, chics, shorts, seafood, all that stuff, now instead of fishing i'm splitting firewood:frown:

[BUIZILLA]

I know that it is hard to think about when you are freezing in front of a fireplace up in TN but just try to remember your youth back in southern FL.....there are still people out boating this time of year!!! yup, did that today, gorgeous weather... I'm starting to like this 33 Powerplay a LOT, but this triple engine around the dock thingy is wierd... threw a set of 27 hydro's on it today and it's a completely different boat,,, picked up like 7-8 mph cruising.... cruising at 73 is effortless... geezus

[SilverBack]

yup, did that today, gorgeous weather... I'm starting to like this 33 Powerplay a LOT, but this triple engine around the dock thingy is wierd... threw a set of 27 hydro's on it today and it's a completely different boat,,, picked up like 7-8 mph cruising.... cruising at 73 is effortless... geezus


Is that boat in your signature? I bought my boat from a guy down in Ft. Myers and he was a manager at a Bass Pro Shop and he told me that their number one selling gun by far was a marine shot gun because if you had a triple outboard boat that it was not if but when you were going to get jacked up by some Pirates!!!! Have you ever heard of that kind of thing happening??

[Last Real Texan]

I am seeing all over the web your desire to raise the X even higher and do some bottom work. Just bring it to me I can fix it for ya...I have an awsome set of tools and a big ass shopto do all the work, I have a really awesom sawzall too. I CHARGE BY THE HOUR....My estimate is it will take 400 hours @$125.00 per....$ 50,000.00 total. Half up front and the balance over three draws....Trust me I can fix it.:rock:


Tex

[BUIZILLA]

and I'll find you a better hull, do the swap, turn key for $35k...

[SilverBack]

I am seeing all over the web your desire to raise the X even higher and do some bottom work. Just bring it to me I can fix it for ya...I have an awsome set of tools and a big ass shopto do all the work, I have a really awesom sawzall too. I CHARGE BY THE HOUR....My estimate is it will take 400 hours @$125.00 per....$ 50,000.00 total. Half up front and the balance over three draws....Trust me I can fix it.:rock:


Tex


I agree with ya on the hours, but my rate is 95.00 per hour.. :pizza:


and I'll find you a better hull, do the swap, turn key for $35k...


Cool. Tex can sub it to me, I'll sub it out to you and pocket the change...


I love you guys!!:bighug:

[BigGrizzly]

I was going to respond to this but I am not. What I will say is If you have enough money you can always find somebody to do something stupid with it.

[Scott Pearson]

Randy....I'm as stupid as they come...send it my way:nilly::wrench::wrench::wrench::wrench:

[SilverBack]

Randy....I'm as stupid as they come...send it my way:nilly::wrench::wrench::wrench::wrench:

Hey..wait a minute...weren't you the guy that wanted to put some special pulley on my Raggazza?????