View Full Version : Bob's vs. Allison's plates
ncst8er
12-28-2002, 12:28 PM
Has anyone had experience comparing the Bob's Machine style of anti-cavitation plate with the Allison style? I know there was a thread about this some time back, each having their proponents; but never any indication of whether one was better or not. From reading the material on the Allison, it claims to be better above 80 mph due to not causing splash back on to the prop. Since my boat would be hard pressed to run 80 even with work, I'm more interested in holeshot. Is the Allison style worse, comparable or better on the bottom-end?
Thanks
vector mike
12-28-2002, 12:49 PM
I made a copy of an Allison plate that works great. However, neither plate is touching the water when you are up on plane unless your motor is mounted really low. Here's a pic of the one I made. It's stronger than the stock Allison plate because of the diamonds on it. A friend of mine has the stock one and it looks like a butterfly in flight because the sides are bent up so high. :rolleyes: Also, you don't want it any longer than the stock cavitation plate because it puts a lot of stress on the stock LU when you jump over wakes. :)
stevek
12-28-2002, 04:06 PM
I have a plastic plate on my 2.5. Where can you buy one of these plates? Or do you have to make it?
Ray Neudecker
12-28-2002, 04:18 PM
The Bob's has better hole shot. On some set ups it will hurt the top end slightly. The Allison has less effect on the top end and not as good out of the hole.
vector mike
12-28-2002, 06:34 PM
How can either one of these plates have an effect on top end when they don't touch the water? :confused:
Steve Zuckerman
12-28-2002, 07:06 PM
Ray is correct as usual on the plane off effects and top end effects of these styles of plates.
More surface area, located further aft on ANY whale tale, will give
more tail lift and better hole shot.
However, the Allison plate is designed not to interfere with the
thrust cone of high speed water coming off your propeller. That's
why Darris has cut it down near the end of the cav plate. Water
is a fluid, but it's an incompressible fluid that is put in a bind when
"shrouded" as it is with a long wide, ride plate.
This may be OK if you are a drag racer who's willing to give up a
couple of MPH for a better ET. But even most of us are not, and
I don't use them. A better approach is a fixed ride plate, attached to your jack plate or hull.
The things that help on top end, don't always help on bottom end, and vice versa.
Regards,
Steve ;)
Redbullet
12-28-2002, 07:32 PM
Bob's plate seems to catch a lot of prop discharge water which could slow you down on top.
JohnR225
12-28-2002, 07:50 PM
To get the BEST of both worlds (holeshot & top speed) You don’t want the water off the prop to hit the foil and you don’t want the foil to extend past the rear of your cavitation plate. I hear the ET Allison foils are great for holeshot and don’t hurt your top speed. The only problem with the ET foils is the powder coating coming off.
I just bought a foil made by Mike Ray and it seems to be the cats meow ... He can put anything you want on the foil or polish the whole thing.
To contact Mike he is at Mike Ray (
[email protected])
http://publish.hometown.aol.com/johnr225/myhomepage/mike%20ray's%20foil.jpg?mtbrand=AOL_US
Redbullet
12-28-2002, 10:35 PM
Thank's for the pic John.
JohnR225
12-28-2002, 11:14 PM
You bet Mike.. Just giving credit where credit is due.
I wish I knew how to shrink that pic a tad ... LOL
ncst8er
12-28-2002, 11:15 PM
The claim is that in a high-speed, surfacing application (such as you describe), the water thrown from the prop hits the Bob's style plate and bounces back into the prop, causing extra turbulence/drag on the prop. That's why the Allison plate is swept forward so that it doesn't increase the surface area above the prop. At least that's what is claimed in the Allison patent application that was referenced in another thread on this subject. Unfortunately it can't be attached because it's a pdf file. Since the patent claimed the benefit to be most noticable above 80 mph, I wasn't that concerned about it in my application, so I was more interested in experience with the holeshot performance.
vector mike
12-29-2002, 09:53 AM
Never thought that water coming off the prop and hitting the plate would cause enough turbulence to effect top end. Guess I learned something new. :D
Techno
12-29-2002, 12:31 PM
I don't know how much affect this is but water is rising after it clears the transom. The boat is still depressing the water even if it isn't in the water at all. This water sprays upward once it can and if it hits anything it is drag. Don't know how much but it is drag. Even if the prop shaft is even with the hull the prop is actually in deeper water than this from the boats angle and this spray. The further the OB is set back the higher the water can rebound around it.
ncst8er
12-29-2002, 12:47 PM
The patent background and the other item mentioned (particularly regardng the bigger foils popular on lower performance boats) is that the force of the water thrown from the propeller pushes up against the plate, forcing the bow down. I printed and scanned the appropriate page and attached as a btmap so that interested parties can download. I assume that since patents are matters of public record that there is no problem with reproducing it here.
vector mike
12-29-2002, 04:31 PM
Do you have the rest of that article? It only shows the first two pages then ends in the middle of a sentence. :eek:
BarryStrawn
12-29-2002, 11:02 PM
Mike,
The PDF of the foil patent is at http://barry_strawn.home.mindspring.com/AllisonPatents/6095875.pdf or you can see a directory of all the Darris Allison patents at http://barry_strawn.home.mindspring.com/AllisonPatents . I stuck them there a while ago for someone on AllisonOwners.com.
I'd suggest right clicking a file from the index and doing a "Save Target As" to the file to your desktop or somewhere convenient. Then open that file - works better off your hard disk than viewing direct from the web.
Barry
FCnLa
12-30-2002, 02:06 AM
I have an Ally wing and am very pleased with it. Other that the paint peeling off, the only complaint I have is I had to modify it to fit my OMC ( Allison's only problem, fitting it to a real motor ;) ).
I have heard they flex some. This could possibly be prevented by using different thicknesses and alloys.
The Johnson wing is some what like the Ally wing (does not extend past the cavitation plate, if it does, not much) is made of stainless steel and looks to be bullet proof. The only down side to it is its weight.
I bought my Ally wing from Baker Marine, ScaryFast.com (http://www.scaryfast.com)
I never liked the Bob's, specifically because it extends past the cavitation plate.
:)
aaron bjerke
12-30-2002, 01:38 PM
I have the Johnson wing on my checkmate Starflight. It has made a huge difference in holeshot and did not affect my top end. Actually i think i picked up a mph or two on the top. It helps with my long boat keeping planed at low speeds so i can pull wakeboards and such. Id say holeshot was cut in half or a little less. I am running a 23p tempest on a 200 merc.
aaron bjerke
12-30-2002, 01:40 PM
Heres a pic of it installed
wj225
12-30-2002, 02:44 PM
Some have mentioned a problem with the paint on the Allison Foil. If you want you can purchase an unfinished version from the folks at Allison. I did this so that the foil would closely match the finish of my Sportmaster.
Bill
hey everyone,
from what i understand these plates are to help planeing.
i was wondering what kind of difference it would make on a smaller boat with smaller power like mine. the boat i have is a 13 foot delta with a 75 OMC stinger on it. would a plate give me any benifits? if so what would my benifits be and what would i be comprimizing?
Pete
ncst8er
12-30-2002, 05:53 PM
Since we have similar boats and power, you've got me curious about the Johnson wing. You got any websites or know of suppliers where I could get info. on it?
JohnR225
12-30-2002, 07:06 PM
Bakers Marina sells the Allison ET foil and the Johnson.
There is no way a foil could help your top speed. It can only hurt your top speed if the water coming of your prop is hitting it.
I also have the johnson wing i got mine from Baker Marine.There website is scaryfast.com.
Jerry Ridenour
12-31-2002, 12:05 AM
if the ally foils dont catch water and hurt top end,why do they wind up being bent way up on the left side?they must be catching some water...
JohnR225
12-31-2002, 12:13 AM
Ally foils (ET plates) don't work so well on heavy boats. They do flex and will bend if you do a bat turn ... On heavy boats they bend over time ..
Shoot Mike Ray an E-mail, his foils are thick and no powder coating to flake off. He has one heck of a foil he is building there for a great price!
aaron bjerke
12-31-2002, 09:07 AM
All i know is that for my Heavy Checkmate, the wing made a huge difference when running a higher pitch prop ( 23 tempest ). I also have a 19p that I use for skiing, but i have to be driving because you can over-rev it. I do run a cmc jackplate and keep it as high as possible when running top end. The wing is really heavy and well built. The only thing i did was to add some weld to the stiffening member across the back of the wing. I havent tried the ally, because this was my first try and i am happy with it. ncs8tr - if you would like, I can get measurements off my wing and you could make one out of a sheet of stainless for less than the 100 bucks bakers wants for them?
ncst8er
12-31-2002, 04:19 PM
I don't know if I'll make one or not, but I'd like to know the measurements even if it's just for comparison purposes. If it works that well with your Starflite/200, it should be a good fit with my Enchanter/200.
Thanks
O/B Dude
12-31-2002, 10:16 PM
Pete,
The plate helps holeshot but also helps boats that have a porpoising problem at low speeds. If you dont have either of the issues, save your money.
Redbullet
01-01-2003, 12:12 PM
I tried the allison foil on my bullet and due to the back tail design It cavitated the prop a little. I cut mine totally different in the back to let more water through and it stopped the cavation. I still have a few mods to due to improve it. Lots of foils out there and most of them have some small flaws that hurt them. I have built a totally different foil that mounts from the front of the gearcase and will be filing for a patent this month. It works really well and does not affect water to the prop at all. Lifts the boat and carries it foreward instead of just popping it up.
Plan to have them for sale by Feb.
shadowman
01-04-2003, 02:50 PM
I know a guy that runs a 2002 ally with a 280 merc and he swears by a fixed plate on his jack plate. It's a custom built plate and I know Its hard to beat. I've seen this boat launch and It's pretty quick. Quartermasters beware!
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