Poorsche

I've got a Formula 357 SR1 with the standard K-Planes (280's I think). THey are 19 or so inches long.

I'm considering upgrading to the 30 inch K-Planes. A friend has the larger ones on his 35 foot Chris Craft.

Anybody gone thie route? Any negative effects? Any benefits?

Back4More

I tried them on our 1993 42 Fountain...It was harder to adjust trim, they were too sensitive and as a result went back to the smaller ones.

martiniboat

I have to agree and disagree with Fred

The 280's are 19" (+ or - 1/4")

I really like longer tabs too since you don't have to deploy them as far to get the desired results, meaning less drag and more speed They can really do wonders for fuel economy too! (stay on plane @ a lower cruising speed)

Poorsche, perhaps someone on the board has a pair of bottom plates that you could swap out just to find out if longer is better for your particular hull?

Brian

martiniboat

One more thing, that's a 'trick' looking mural you have there Fred!


B

Poorsche

Based on what you say I like the idea fo the longer tabs. If anyone has a pair to swap or sell I'm in need.

tcelano

The longer tabs will help you in rough water, and will appear to respond quicker due to immersing the tip at a lower angle of attack. Due to its lower aspect ratio, the longer tab is actually a less efficient lifting surface, but one that can exert more leverage toward trimming the boat.

I'm in the process of developing a set of really cool carbon fiber/epoxy tabs. I hope to have them tested by spring. They will the ultimate in trim tabs, with a 100% 316 stainless steel ram. No Aluminum here whatsoever. They will be offered in black carbon, as well as with the red/black, blue/black, green/black, orange/black or yellow/black carbon/Kevlar weaves. The Kevlar will be purely cosmetic.

I am working with the finite element models now, and spec'ing them out to handle a full 20 degrees of deflection at 100 mph, with a factor of safety for bending moments still above 3.0. That condition results in slightly over 12,000 lb of lift per tab, and as much hydraluic pressure in the ram as the pumps can hold before relieving. This kind of condition would only be present during a stern-first re-entry at high speed. I'm using some of my published research on trim tab lifting and its affect on stability in the design to accurately model the pressure field experienced on the underside of the tab. The carbon has the potential for a lighter structure than Aluminum, but I'm building these for the long-haul.

For those of you who think 19" is not long enough, but 30" is too long, these will be 24" from the hingepoint to the tip, so just over 25" as measured from the transom, with the same 14" root span as the Merc.

Please excuse the graphics, but the completed model should look something like below. The goal is to make something that will look good next to, say a #6 drive...

Anyway, keep your eyes peeled. I hope to have them out the door for a reasonable price, including rams and pumps. I'm hoping to be able to sell them for cheaper than you could get a set of 380's.

Poorsche

Your renderings look great. Hopefully you'll have an option to retrofit K-plane transom mounts so all you need to replace are tabs on existing installation. As you probably know to replace the whole system is painful. There's a market out here to just replace the tabs.

offthefront

iTrader: (1)

$$$$

tcelano

Here are some more renderings in various colors. I would definitely like to be able to retrofit onto the K-plane bracket, but it is very difficult to make a carbon shell structure which will transmit the loads correctly to the three hinge tabs of the K-plane. I also know from first -hand experience that removing the hinge pins from older K-plane setups can be difficult if not impossible without destroying stuff. I am going to work to try to make the transom bolt pattern match up at least.

It is also my goal to make these setups financially attractive for retrofits as well as new construction. They will use the same pumps and plumbing, and will be capable of accepting the Merc ram, so I should be able to sell a bare bones tab fairly reasonably.

tcelano

Here are the other three colors