Building a tunnel tab

[Mr. Demeanor]

Going g to build a tunnel tab to help keep the bow down on hole shot. My tunnel is 34" wide and I found a 36" x 9" Bennett trim tab that would work perfect but its solid stainless and weighs 15 pounds.
I could use some advice one what thickness aluminum to use. I will bend 90's on the ends to stiffen it up and add some braces out of angle. I plan to attach it with a piano hinge and use threaded rod and Heim joints to make the angle adjustable.

The transom has a notch at each sponson so it wont be a true tunnel extender. It will only extend the top of tunnel and work at slower speeds where I need it. More of a big trim tab over the tunnel than a true tunnel tab.

This is an old pic but you can get an idea.

[afr]

why not use carbon fiber and press mold it

[MCRacing]

You have no idea of the forces on a tunnel tab even when its up, on my 21 Skater the Merc K tab has broken multiple times from not being stout enough. I have had the ram push rod break and go completely through the plane, the forces back there are incredible. My point don't use cheep crap, TT are very dangerous. Good luck see you in Key Largo

[MCRacing]

Aluminum/stainless will probably look like a piece of spaghetti after your first run if it's anything like the skater

[Mr. Demeanor]

This isnt a boat I run in rough water and I can imagine the pounding it would take. What Im thinking is more like a skid planer I see on the bottom of some jackplates I guess.

[afr]

mc yes the heavier the boat the rougher the water the more stuff breaks i seen clamps break lower units snap in half all kinds a fun stuff
but for what he is doing pressed carbon would hold up even if he did get a little rough on it

[Instigator]

I think it's the Argo 23 that I saw a rubber one on.
I think thats genius. It appears to be a very rigid rubber, almost like a car tire side wall. W/the proper thickness/rigidity, you could get it to do it's job plus also have it blow open @ speed and reduce lift to prevent any surprises @ speed
I remember the story of a offshore team back in the day, putting them on their 24' Skater then tripping/stuffing it and killing one of them.

On strength, I made skid plates for the bottom of the jack plates on my old 24' Sonic. After the 1st weekend on Lake Erie those plates looked like you pounded the bottom of them w/a leather hammer and they were deformed all the way around the perimeter of the plates.
Amazing.

[dagodiver]

like i said already if you can bend it ie; 5052H32 or the like it is not going too stand up to the punishment of 90mph fun.
Yes i now you can do some heat treat to some other sheet metals and such but that is a ton of work.
I offered to machine it out of billet stock of your choice ie; 6061T6 or 7075 I can gut it all out to make it just as light.
Have you noticed how heavy duty K planes and tunnel tabs are.? just a thought.

Dago.

[Mr. Demeanor]

I think it's the Argo 23 that I saw a rubber one on.
I think thats genius. It appears to be a very rigid rubber, almost like a car tire side wall. W/the proper thickness/rigidity, you could get it to do it's job plus also have it blow open @ speed and reduce lift to prevent any surprises @ speed
I remember the story of a offshore team back in the day, putting them on their 24' Skater then tripping/stuffing it and killing one of them.

On strength, I made skid plates for the bottom of the jack plates on my old 24' Sonic. After the 1st weekend on Lake Erie those plates looked like you pounded the bottom of them w/a leather hammer and they were deformed all the way around the perimeter of the plates.
Amazing.

I also saw the rubber "flapper" style tab on the Argo. That boat has a VERY deep tunnel though. Mine is pretty shallow at 5" so just the mounting could take up 20% and Im not sure I want to test that.
Another idea is to just use two small trim tabs, one on each side of the motor at the top of the tunnel. I even thought about using the Smart Tab actuators which are spring loaded.
http://www.nauticusinc.com/smart_tab..._trim_tabs.htm
During holeshot they provide some lift, on plane they would be up out of the water, and in choppy water they have some "give" being spring loaded.

Mike, Im knocking around ideas here and looking at options. This is more of a fun project for me and not something I really need.

[lance]

I've made a couple of skid planners from plastic kitchen cutting boards. You can buy them off EBay in a variety of colors and sizes up to 36". The 3/4" thick size works well. The plastic is easy to cut and finish. I use anodized aluminim angle from a home store and stainless nylon lock fasteners.

[Mr. Demeanor]

I've made a couple of skid planners from plastic kitchen cutting boards. You can buy them off EBay in a variety of colors and sizes up to 36". The 3/4" thick size works well. The plastic is easy to cut and finish. I use anodized aluminim angle from a home store and stainless nylon lock fasteners.

Nice. My jackplate only has about an inch of setback so theres no room to mount one like that. That type of material having some flex might be a good option but then again, its probably heavier than just using the Bennett trim tab. Mine is goint to need a very deep notch in the middle for the engine.

With the engine tucked in I have 3-3/4" between the tip of the lower unit and the transom. Looking at this, I could put about an 8" wide trim tab on each side centered directly under each side of the jackplate. Then just run a threaded adjuster up to each side of the jackplate.



Motor turned fully to starboard:

[Mr. Demeanor]

This would do the trick. Ill have to see how heavy they are.
http://www.ebay.com/itm/Brand-New-Be...20625e&vxp=mtr

[Mr. Demeanor]

One other idea and I gotta get some work done...
This gies back to the rubber flapper on the Argo.
What about a single Volvo QL trim tab mounted right over the tunnel? It simply deploys a blade straight down and would be adjustable. It would not blck off any of the tunnel unless I wanted it to.
http://great-water.com/store/product...c-184_185.html

[Mr. Demeanor]

I have two of these 8x10 sport tabs coming. Because of the way they are bent, they are made of lighter gauge stainless steel and only weigh 3.5 pounds each. $140 for the pair.
I got them direct from Bennett Marine. They have a "scratch and dent" pile and he pulled two nice one for me. Ill probably have them polished up anyway.

stay tuned...

[Mr. Demeanor]

Tabs are here (need to polished) and I have an idea now how it will work.
The tabs can mount centered under the ends of the jack plate. Motor has over an inch of clearance to tab turned all the way.


I need an adjuster to go from the tab up to a hole in the bottom of the jackplate kind of like I sketched in red.
Maybe something like this?

http://www.amazon.com/Amico-Thread-S...QFQ8YWXCKJYVBS