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Delta pad

44K views 62 replies 24 participants last post by  75 fantasy 
#1 ·
What is it and what does it do ?

I keep seeing this pop up every now and then and im just curiouse
 
#2 ·
A delta pad makes a flat surface towards the back center keel line of the boat for an outboard to have a surface to ride on. Works great on a fast bass boat or something like that. Some of the early jets were built that way before they realized that the rounded bottoms worked much better in a jet boat for loading the pump. They can be made to run pretty good. It's just a lot easier to make a fast boat run and load the pump right with a rounded bottom. If it's a boat that runs under 70 MPH, it probably don't make that much difference.
 
#3 ·
From what I was told, they had used the Delta pads on everything from outboards to stern drives and on jets as an attempt to improve the out of the hole performance and lower the planing speed on modestly powered powerboats. They seem to have really gained in popularity when the states started imposing the 35MPH lake speed limits and the fuel crunch...

They really did not "add" to the performance of the boat as far as the everyday 60 MPH cookie cutter, but when heavily modified had detrimental effects as far as high speed stability (read; chine walk)..

I totally agree with Duane on the "no worky on the jet hull"...:)devil

I have seen a couple of Bahner jets with the Delta pad and they do seem to stay on plane at a lower speed, but really never noticed anything else that would make me desire a hull wiith a pad.

GT :)hand
 
#8 ·
Thanks Glenn:)devil









I was always wondering how do you know or what do you go by.. I really want to start setting this boat up this next week.. Lots of test runs and what nots.

Gonna try some runs with a droop with ride plate then some without and i really want to try a snoot to.

maybe i should start with a rock grate ? and change out that loader.
 
#12 ·
IMHO "right and wrong".

Delta pads create 'false rocker', and that makes the hull ride with a 'nose up' attitude. This makes the strakes 'attack' the water at a greater attack angle. (LIFT) Some builders/racers used them on hulls that did not require them, or hulls that could not use them correctly. "Loading the pump" is easily done with a TEAR DROP in front of the intake. (for drag racing) Much of the problem lies in the use of a delta pad on hulls that have shallow V sections (deadrise) This 'false rocker' causes the water from the center to HIT the outer chines and cause 'tail lift' at higher speeds. I know because I set up a 440" injected Chevy BB, Berkeley jet, in a Hondo Pantera 17' 10" hull. It ran 109 MPH and was suffering the 'tail lift' at those speeds, back in 1985. I'd like to see a 1 degree pad on a Rodgers boat, I think it would run very well. Big wide pads do suffer unloading in rough waters, but narrow (enough width for the weight) pads do not.
 
#13 ·
i'm interested in hearing more on the delta pad, my boat has one, 1981 Baker custom boats, gps around 67 and mild bbc power. how fast can it go before i see a loss as far as vs. a round keel. cool floor in tho.
 
#27 ·
Lots of alloy boats with delta pads but typically ones that use axial pumps as the intakes are designed for a flat bottom boat. They work fine for jets if the boat is designed correctly. They most certainly give more lift than a radius keel altho as has been mentioned they definitely arent as easy to keep a pump loaded at high speeds.

The Taylor pic is good, here's another. Usually the delta extends almost all the way forward to where the stem starts curving up. As you can see this actually means the keel is "tapered" towards the back in relation to the height of the hull at the chine. Sprint boats have delta bottoms
 

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#29 ·
That loader is way deep. Needs to be trimmed back.
This is the biggest problem with a delta bottom that I see. I realize they can be made to run 93 mph, but a lot of times it takes so much loader below the delta pad on a fast boat to make it load the pump that it can be dangerous on shut down. They can be made to work. It's just easier with the regular radiused jet bottom. I was not tryinig to knock anyone's boat because it had a delta pad; rather trying to explain the difference.
 
#30 ·
Steve , put you boat on flat clean level surface (Garage floor etc) Then run a good straight 3 to 4' edge on the keel ahead of the loader intake area , holding the straight edge in place agianst the where it intersects the front of the intake area check the horizontal leading edges of the loader ramp blades versus the top edge of the straight edge (also extend it back and check the center biting edge of the shoe, even if your shoe is "fixed", always curious ) you can use a sawzall or ? to trim the loader blades then grind to reshape or if neccesary they can be welded to add material as well . try to get a "eyeball" as to where the backs (trailing edges) of those ramps approach the face of the impeller also we find lots of them wrong (weld or jig issues). btw this is different for Deltas :) Tom

btw it looks like you may have the original 1/4 x20 bolts on the loader? recommend you overdrill and thru bolt use a little silicone as thread locker and sealant on the loader pad too

PS your loader looks like what we call a "river racer" type , check it real thoroughly for weld integrityalso recommend you drill and tap your suction for intake data readings too
 
#52 ·
btw it looks like you may have the original 1/4 x20 bolts on the loader? recommend you overdrill and thru bolt use a little silicone as thread locker and sealant on the loader pad too

PS your loader looks like what we call a "river racer" type , check it real thoroughly for weld integrityalso recommend you drill and tap your suction for intake data readings too

Tom i cant get one ***in bolt out so i have to drill it anyways....

What would be the right size 5/16 ? 0r 3/8

Thanks steve:)devil
 
#34 ·
I have a Cole 20' SS with a delta pad bottom. When I installed a river racer style intake grate, I gained about 5 mph. My tip of blade hangs down 5/8 inches. That seemed kind of deep. My boat really likes the extra water. Should I trim this back? Looking along the angle iron edge it aims the water at the base of the shaft. Is that were it should be? One thing I did notice is that the loader is built for a intake for a v-bottom . Mine is flat between fins. The fingers of the loader sit slightly below the biting edge of the intake. Is that a problem? Boat rides nice.
 
#35 ·
I am of the mindset of "if it works, leave it alone", however to properly answer your question, some data logging would be in order, without intake pressure readings it is virtually impossible to say for sure whether or not you are at the optimum point...5/8" sounds deep to me, but 5MPH is huge IMHO...

GT :)hand
 
#37 ·
Delta

The trick to making a delta pad to work is that you have to go down and get the water unlike a radiused keel bottom. The delta rides on top of the water and the radiused keel breaks thrugh the boundry layer of water and loads the pump. That is why you run the shoe slightly above the keel and with the delta you can run the shoe below the keel.
 
#40 ·
My 77 Brendella has a delta pad. I will be installing a shoe and a rideplate. Should I start out with the shoe even with the delta pad and then shim down from there and how much is to much below the padwhen adding shims to the shoe? Also I was told by a few people not to do a set back on this boat, but they couldn't tell me why mabey you could shed some lite on this subject.

Thanks,
Ironman

The trick to making a delta pad to work is that you have to go down and get the water unlike a radiused keel bottom. The delta rides on top of the water and the radiused keel breaks thrugh the boundry layer of water and loads the pump. That is why you run the shoe slightly above the keel and with the delta you can run the shoe below the keel.
 
#49 ·
With the delta pad bottom would you want to to keep to boat flat on the water at speed, or would you try to keep the nose up like a v-bottom? What do you other delta pad owners do. If you have a place diverter where does your nozzle sit when cruising. Down, up, or straight? What about rooster tail?
 
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