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Optimizing Turbofin Performance http://www.hobie.com/forums/viewtopic.php?f=11&t=10176 |
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Author: | Yakaholic [ Mon Jul 28, 2008 6:21 am ] |
Post subject: | |
I can only agree wholeheartedly with your findings. Many months ago I took the 2 Adventures with turbo fins to Rainbow River. We had to pedal upstream against a 1-2mph current and after 1/2 hour the turbo fins were wearing out our legs. Removed drives and saw that the clew adjusters were very tight. Loosened them up and we both noticed a remarkable difference. Easier to pedal but without any noticable loss in speed. No speed runs or time trials done by me; I was pretty well convinced by that river episode. Thanks for your testing, pics and confirmation about the clew adjusters. |
Author: | JimL [ Mon Jul 28, 2008 9:58 pm ] |
Post subject: | Even better... |
I bought some longer stainless screws (with nylock nuts) for the clew, to allow more rotation of the fin. I turned the middle of the screws down slightly (hourglass shape) and put a thin rubber ring on each side (of the adjuster screw eye) to keep it quiet. You can shape the screw down (just enough to get rid of the threads in the middle of the slot) on a grinder or even with a hand file.... it only takes a little to free up the motion. This allows even lower pitch of the fins; much more in keeping with our relatively slow boat speed. Just look at a good sailboat prop, and the little light bulb will go on over your head (nobody else can actually see that little bulb, you know). This little trick has been the BEST improvement I've found (after the Turbo Fins). Try it yourself, only costs a couple bucks. Regards, JimL |
Author: | rx7vt [ Tue Jul 29, 2008 5:43 am ] |
Post subject: | |
Any chance of a photo? I'm trying to organize myself to get a bunch of hard data on mirage drive performance under various conditions, and I'd love to try your mod. I think I understand what you're describing, but you only provided a couple hundred words, and we all know what a picture is worth |
Author: | rx7vt [ Wed Jul 30, 2008 4:53 am ] |
Post subject: | |
So - tried adjusting my ST trurbo fins as suggested. I agree that it seems to require less effort at low to moderate speeds (up to about 4.5 mph). However, it seems to me that it also requires a slightly higher cadence, especially as speeds get higher. I haven't yet tried anything scientific, since we had brisk winds and a rough chop on top of good sized waves and my bow kept getting submerged. Tough to get meaningful numbers. Has anyone else seen this effect? I think what we really need is an adjustment that tightens up the clew as speed increases - essentially a variable pitch prop. I'll add that to my list of design features for my titanium / carbon fiber mirage drive replica |
Author: | rx7vt [ Thu Jul 31, 2008 3:24 am ] |
Post subject: | |
Thanks for the pictures. Looks like another mod I'll have to try. I guess I wasn't clear about my cadence question. I did figure out early on that faster cadence means faster speed What I was trying to say is that with more slack in the clew adjustment, it requires a higher cadence to go the same speed than it does with less slack. This difference seems more noticeable to me at higher speeds. Just wondered if anyone else had the same observation. I also have the variable pitch concept, I think. The harder you push, the more the clew deflects, and the steeper the pitch - sort of like using a lower gear. This is exactly what you want when accelerating from a standstill, for instance. I'm wondering if the ideal setting for higher speed cruise might be a bit tighter, though. |
Author: | Fastfish [ Fri Aug 01, 2008 10:26 am ] |
Post subject: | ST or Turbo ST |
I'm still a little on the outs on the the Turbo fin thing it seems like some have many problem with them. I feeling like they(Turbo ST fins) may be putting a bit too much of a load on the drive system the ST's work good and can be adjusted. Are the Turbo fins really worth the appearent teething problems experienced by some I know some have said they will never go yakking without they're turbo fins so lets hear some more thoughts on this subject. |
Author: | KayakingBob [ Fri Aug 01, 2008 1:24 pm ] |
Post subject: | |
I'll never go yakking without my turbo fins! Kayaking Bob |
Author: | rx7vt [ Fri Aug 01, 2008 1:27 pm ] |
Post subject: | |
I tried to address this in another thread with a list of reasons NOT to get the ST Turbo fins. Reason number 2: 2) If you have really strong leg muscles and testosterone poisoning (or are likely to loan your 'yak to someone who does). The Turbo offers enough resistance to place a good deal more strain on the drive. I think Hobie has made changes that strengthen up the weak spots, but if you want to prove how strong you are I think the Turbo fins give you a better chance of breaking the drive. If your interest is 100 yard sprint races, I'd worry a bit. For normal use they seem to be fine. |
Author: | Yakaholic [ Sat Aug 02, 2008 10:00 am ] |
Post subject: | |
While on the subject of optimizing the drive I do have a suggestion. One of the biggest beefs I have with the Stainless Steel Sprockets is the mast wobble even if the cotter pin is new. The wobbling mast justs gets worse over time enlarging the hole in the SS sprockets even more. This HAS to be a real loss of effeciency. Yes, I prefer the SS over the plastic sprockets. My heavy turbo fin use, coupled with the ability to strike objects, re-straighten the mast and keep going are better than taking a chance of cracking a plastic sprocket. I am very happy Hobie decided to keep making the Stainless Sprockets to keep us power users happy. Now, how about just welding the turbo mast to the SS sprocket?! Don't bother cutting notches or drilling holes in the turbo masts and don't bother drilling hole in SS sprocket for a cotter pin - both saving on machine shop work. Weld the turbo mast to SS Sprocket - making it one unit. No cotter pin to break! No more mast wobble! Solid, Stable, Strong! Bent masts will just get straightened in a vise. You can even make a non-turbo version combo, but the real beneifit is for the turbos. So how about it Hobie? Can we PLEASE get a SS sprocket & turbo mast as 1 piece? Put me down for 4 units (enough for 2 drives) |
Author: | Roadrunner [ Sat Aug 02, 2008 10:32 pm ] |
Post subject: | Re: ST or Turbo ST |
Fastfish wrote: Are the Turbo fins really worth the appearent teething problems experienced by some I know some have said they will never go yakking without they're turbo fins so lets hear some more thoughts on this subject.
If performance is important to you, get the Turbos. If you don't want anything to happen to your drive, lube, inspect and maintain it regularly, just like you would any mechanical device. If the Drive is going to have a problem, 9 out of 10 times it will give an advance warning. Even then, 9 out of 10 failures the Drive is still operable and can safely get you home. Your chance of having a problem with Turbos, especially with the "08 drum upgrade is very small. IMO, the only current potential issue with Turbos is the possibility of a mast wallowing and eventually slipping out where it inserts into the sprocket. Not only does it give ample warning, but is easy to address with a dab of epoxy in the shaft. STs aren't a bad alternative, and standard fins might be a best choice where the environment is going to beat up the fins (oyster bars, etc.). But for speed, range and acceleration, Turbos are the way to go. I've been using them for over 2 years now (since they first came out) and absolutely love them! |
Author: | Roadrunner [ Sat Aug 02, 2008 10:58 pm ] |
Post subject: | |
Yakaholic wrote: Weld the turbo mast to SS Sprocket - making it one unit.
No cotter pin to break! No more mast wobble! Solid, Stable, Strong! Yak, great thought. I wonder what a welding shop would charge to tack them together vs. the price of a new set. I have done something similar with the newer Drive (with '08 drum and cable upgrade) as a preventive measure, using epoxy. So far they've been rock solid. |
Author: | kepnutz [ Sun Aug 03, 2008 5:48 pm ] |
Post subject: | |
In two years of Turbo Fin use I've only had one problem after slamming into an unseen submerged object, at full power in ,San Francisco Bay last spring. It would have broken the mast on any other size fin as well so its not really a Turbo fin specific incident. However $15.00 in parts and my labor fixed the sprocket and mast and there have since been no other problems to report . I also used a blue thread locker on the set screws that hold the masts in place and have no issues with hole hogging of the nylon mast sprocket to report as well. Our Turbo fins have simply been trouble free and our mirage drives as well have had no serious issues . Kepnutz |
Author: | stringy [ Tue Aug 12, 2008 4:40 pm ] |
Post subject: | |
Thanks Roadrunner for explaining the tuning of the turbo's. After following your advice I realised I had mine up way too tight and loosened them up. Made pedaling much more comfortable! Looks like Hobie's new sprocket/mast reinforcement is another step towards bulletproofing the drive. Thanks Hobie for the ongoing improvements! |
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