squirly at high speeds...

[scorpien boats]

I just got back from running my boat and I kinda loose controll when it get past 3/4 throttal.... I was thinking a runner or like two turn fins could solve this problem, I know prather makes something called spin fins but im looking for something bigger does anyone know where i can get something like this or something else to solve the problem.

I think I have just fell in love with gas boats... i forgot to bring a camera :(

thanks for the help

[BurnZ]

Which boat? You may need some ride pads to force the nose down a little. Turn fins help the boat to dig in a little instead of the rear sliding or skidding in turns. Too big a furn fins and you could roll the boat.

Aeromarine has some: http://aeromarinerc.com/

Offshore: http://www.offshoreelectrics.com/MainPage.htm

[Mike T]

Most large monos, especially gas monos, need a turn fin or two. The one shown on the Donzi in that Aeromarine link is about the right size, although it should be mounted at 90 degrees to the plane of the bottom, not vertical to the hull as shown there. They are easy to make if you can find the metal - say an aluminum angle and a piece cut from aluminum flat stock, an aluminum ruler, or an old street sign. Or buy two from aeromarine.

Here's an example:

http://forums.radiocontrolzone.com/attachment.php?attachmentid=47551&stc=1

[Doubledog]

Mike & others. My Gator starts chine walking at high speed like Scorps boat. You can lower the right tab & it will balance out & go like a dream. Just seems like when you lower it even an hair, it robs speed. We've played with this doing the smallest adjustments, props are razor sharp & thinned. Do you think the turn fins would assist in this?

[scorpien boats]

i don't have trim tabs yet im going to order them from somewhere soon...

the boat im talking about is my 50" deep vee

[Mike T]

Fins prevent hopping in the turns but do little for chine walking. Some hulls are going to chine walk no matter what you do. John Finch suggests mounting the entire strut (or drive) and shaft assembly about 3/8" to the right of the hull's centerline and making sure it is aligned parallel with the keel line (in other words, points straight back). This will compensate for propwalk so you don't need left rudder to go straight and also has a damping effect on chine walk. Lowering the tabs brings the nose down so it scrubs off a lot of speed. If you lower the wrong tab, it can make chine walk worse. Also check the bottom for hook (concave areas). They can cause chine walk and a number of other problems.

[CFRACR]

Fins prevent hopping in the turns but do little for chine walking. Some hulls are going to chine walk no matter what you do.

Lowering the tabs brings the nose down so it scrubs off a lot of speed. If you lower the wrong tab, it can make chine walk worse.


I don't know Mike but you confused me here! :confused:

I think tabs have a good bit to do with chine walking. I had a boat that chined like a son of a gun. I made three different sets of tabs with different lengths & widths. Well lets just say the third set worked & I have no chine walking now! :)

[ejp]

could that be because you lost the speed for the chine walk by creating so much drag?

[Mike T]

What I'm saying is that turn fins don't do anything for chine walk on the straights. They can prevent hopping and spins in the turns. Tabs can stop chine walk it or make it worse depending on what's causing it in the first place. Tabs really can't compensate for a wavy bottom surface.

Anytime you add fins and tabs, you should first use a straight edge to set then straight (parallel to the bottom's line of travel) and after testing, use only minor deflections of the tabs to make control inputs. If it takes more than a tiny bit, you will have other troubles. For instance, too much down trim on just one tab will tend to rock the boat over to the opposite side, starting the cycle of chine walking.

About hook and rocker: I was helping a friend set up a little .21 mono race boat once and we found it to be a real handful to drive. It would chine walk down the straights and oversteer in the turns. Tabs helped some, but a closer look showed some odd irregularities in the bottom. Areas of hook here, rocker there. A Saturday of bondo work took care of the bottom and the boat handled a lot better.

[Doubledog]

Checked the hull & she's good. Usually have ran the tabs on just for looks or nothing at all. I like it to run loose & nervous. :D As I'm playing by myself most of the time it makes it interesting. Then this summer I met up with the German guys & Klaus wanted to help me trim it in. We lowered them till it ran fast but seemed stuck on the surface. Speed scrubbed off a little to where it was noticeable but the hull was predictable.

Thanks for answering the question about the turn fins. If the bug hits to circle race, then we might consider some.

[97TRAKIN]

We lowered them till it ran fast but seemed stuck on the surface. Speed scrubbed off a little to where it was noticeable but the hull was predictable.

I lowered mine some also and together with the shortened stinger drive it's running much better. I lost a little speed but it's much more fun not having to go fishing for it EVERY time I run it. I also use a turn fin can't imagine running without one. I get a little chine walk in the turns but thats about it. No wanting to spin out even in race water conditions.

[Doubledog]

So you like the turn fin also. Its being considered. How long is needed for the gassers?

[97TRAKIN]

So you like the turn fin also. Its being considered. How long is needed for the gassers?

How else would you be able to corner at full throttle :D ?

Mine is about 2-1/2" long and about an inch wide. I made the dept adjustable.

[scorpien boats]

so what should I do?

[Doubledog]

How else would you be able to corner at full throttle :D ?


You do that? :D

[scorpien boats]

ok!, so 2-1/2 and one inch wide will be good?

[97TRAKIN]

You do that? :D

I take it you've never been in a heated sanctioned race? Almost all the cats corner at full throttle like their on rails and some of the monos
(mostly AC Lazers) do the same. The corners can make or break you in a tight race. What good is 50+ down the straights if you got to almost drop off plane to make the turns.

[97TRAKIN]

ok!, so 2-1/2 and one inch wide will be good?

Ok it's 4" long and 1-1/2" wide. but only about 2" is below the stern. I got extra holes in the mounting bracket so I can adjust the dept of the fin to suit the water conditions. Works for me.

http://memimage.cardomain.net/member_img_a/328312_117_full.jpg

[scorpien boats]

I run with a rc club, but not races...

thanks for the info

link dosn't work for me :(

[Mike T]

On my race monos the right fin is about 2-3/4" in the water (below the running surface) and about 1-1/2" wide. That should be plenty. The depth is to prevent it from "disenging" if the boat hops in the corner. The left one is about 1-3/4" in the water and 1" wide.

[97TRAKIN]

Try this one.
http://memimage.cardomain.net/member_img_a/328312_117_full.jpg

[Doubledog]

Was just pulling your leg with that last statement (hence the huge grin). :D

Haven't raced in almost 20 years. Even then it was mainly the outboard tunnels.

[97TRAKIN]

Was just pulling your leg with that last statement (hence the huge grin). :D

I know :D :D :D .

[scorpien boats]

nope link still did not work...

[97TRAKIN]

Why can't I post pix from my hard drive, not even [img] code works for me anymore? :confused: :confused:

[scorpien boats]

it brings me to the thing and says i need some kind of password or somthin..

[mjmsprt40]

Why can't I post pix from my hard drive, not even [img] code works for me anymore? :confused: :confused:

For the life of me, I can't figure it out either. One thing, posting pictures on another site that requires you to be a member of that site stops a lot of us from seeing them... at least until we become members of that site. Now, let's see if I can make this critter work:

[97TRAKIN]

One thing, posting pictures on another site that requires you to be a member of that site stops a lot of us from seeing them... at least until we become members of that site.

I've been posting from my hard drive and linking from cardomain to this site for a while now. I have no clue as to what is going on all of a sudden but I will figure it out.