Turbo Fin Installation Questions

Hello All,

I am in the process of installing the Turbo Fins on my Mirage Drive.
So far I have come into a few obstacles.

1st. the flat spot on the mast is too far down, and will not allow the set screw to fit within the flat area.
On the advice of Hobie, I managed to take a file to the area to elongate the flat spot area to resolve this issue.

--Heres my question.
Now that I have the Mast installed, The Turbo Fin itself will not slide all the way up to sprocket.
-There is a gap between the top of the turbo fin and the sprocket, and about 3/8" of Mast is exposed and showing.

Is this normal?
Can someone please post a Pic of a completed turbo fin installation for reference?

Thanks in Advance
Billy V

The turbo fins (Rubber sails) Dont fit all the way up like standard one's do. This is normal. Just make sure you dont over tighten the screw through the clew screw (eye bolt) too tight when you put the nylon insert nut on. The black plastic chain/sprocket guard that the fin attaches to with these screws needs to rotate freely on the main shaft. To test it just grab the trailing edge of the fin up near the top where the mast inserts and move it back and forth to check that the assembly moves freely. If it seems tight then loosen the nylon lock nut up a little, you only need a couple three threads past the top of the nut..etc..etc. I put some blue lock tite on the threads of the clew screw/eye bolt during assembly to make sure the brass adjuster nut does not loosen up while pedaling. I had to file my mast slot also so the set screw would seat into the notch. Make sure you dont over tighten that set screw either, just snug it up firmly. I have had zero problems since I put them on. There are a couple more threads in this forum that have addressed all these same issues with the turbo install. They might be a page or two back but they all have good information so check those out too.
Have fun out there
-kepnutz_

I wanted to post a pic to show the actual space between the sail and the sprocket I was describing.

Is this a normal sized gap between the two pieces?

-------------------------------------
I have to ask why???

By simply grinding 3/8" off the mast, it would allow the sails to Fully Insert into the sprockets creating aquatic efficiency.

-Wouldn't the gap create aquatic inefficiency?

Is there any reason you can think of that would lead you to believe my above statement would cause a problem with the Turbo Fin operation.

I wonder is mmiller can answer this.

Hi Billy and welcome to the forum.

No doubt, Matt could answer this better, but here's some rudimentary information:

First of all, your installation looks excellent. Don't worry about the hydrodynamics at the base (foot) of the fin, as most of the thrust occurs on the other end where more flexing takes place. Remember, some of the older drives are shaped a little differently and the fin has to work with all versions.

Second, you don't want to alter the length of the mast, because it is critical to adjustment process. The fin "winds" up the mast as it flexes. Once tensioned against the tip of the mast, the wind up ceases and flexing becomes more restricted. The clew adjustment controls this process; as you tighten the knurled nut, you begin to limit the wind-up and therefore the flexing. If you were to shorten the mast, you would defeat this whole process, and lose some of your high speed performance.

Looking at your picture, I'm guessing the clew is about 1/8 inch into the slot, and the luff (leading edge) can slide a little bit in and out. If so, that's about right where it ought to be, in my opinion.

Thank You For All Your Assistance and the Welcome.

I have gone back a few pages to read prior threads on turbo fin installs. I see your point about flex and stretch. I have confidence in Hobie engineering and can hardly wait to test them.

-I really wish there were All Stainless Components, sprockets, etc. for the turbo fin kit. Maybe Hobie will offer a true High Perf Kit, or an upgrade in the future.
-------------------------------------------

In other events......

I used the boat for the 1st. time yesterday in Mission Bay and really like the way it paddles and peddles. It was windy and the water was choppy where the jet skiers play. The boat handled it all VG.

I even got a chance to tow a sail boarder that was in distress a full 1/4 mile into the wind, back to the beach by the Hilton.

It seems an older fellow on a sail board got himself into trouble because of the high wind. He was exhausted and hanging from his board by 1 arm as I peddled toward him. He was not wearing a PFD.

I asked him if he was OK and he didn't even answer me the first time. I took off my pfd to give him, but he refused it. I put the yak next to him for a minute to make a quick game plan.

He asked if I could please tow him in. I didn't know if I could given the size of the board and sail that were laying in the water, plus the weight of the big man (I go 180 lbs, he was much bigger) he couldn't even crawl back onto the board, so I towed the whole mess just the way I found it.

I had a 50' length of 3/16ths nylon on the yak. I tied it to the board, and made several loops around my hand for cushion. I had it draped over my pfd so it wouldn't cut into my shoulder and off we went.

Slow and steady, but it pulled the whole deal. I had the standard drive fins on the mirage. I had to stop once to recover, but I got him to knee high water and he was ok from there.

It was an interesting day, and a very through test session.

We have made a 1/4" adjustment in mast length since the original introduction of the ST Turbos, so maybe you can cut it shorter. My drawings show 13.94 inches.

On the stainless components idea... we used stainless sprockets in the past. We went to injection molded sprockets for a variety of reasons. Better chain retention was one. The new sprockets do not allow the chain to slip as they did when they were stainless. The new ones do not require bearings against the shafts and last longer because of it. If they do wear, they are inexpensive to replace. The new sprockets do not wear the chain as much. The new parts are less weight.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Matt,

Thank You for your response.
Can you post a picture of the completed turbo fin installation for reference? The one with the newly adjusted mast length.

Before I cut the mast I would like to see how the sails fit into the sprocket covers, and how the chain aligns with the sails, and if cutting the mast will present any other issues.
-A picture would really help clear up any questions.


As you have read I had a couple of issues with the turbo fin kits I purchased. There was nothing in the directions that address either of the issues I was having. I was advised by a tech support person in Oceanside to elongate the flat spot on the mast with a file.
-I asked him about the mast length and he said not to cut it down, and told me to refer to this forum for pictures of a completed installation.

15 Days ago we purchased 3 Hobie Adventures from our local dealer, and I am now having to deal with 'Well Strengthening Kits' as well as 'Turbo Fin' fitting issues. So any help I can receive here is greatly appreciated.

These boats will be fished off La Jolla Shores, so I want to be sure everything is up to par before commencing in the ocean.

Respectfully
Billy V

Drive with current fins installed.

Unfortunatly, I don't have a drive here to take a picture of, but will work on that.

Yes, you can cut the mast length the 1/4". The current dimension looks to be 13.94 inches.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)