Flex or solid shaft

[Norwest]

Your angle of s/tube is too much and will drive bow down a lot. Remedy: Remove s/tube completely and gently bend brass fairly close to where the s/tube support is. What this does is to make the s/tube almost parallel to keel and down 3 or 4mm down at prop. Since you have flex, things will get simple as ****. Your m/mount will have to be slanted so the top of mount will be angled downward but the base remain where it is but not epoxied in. Now take the flex and insert fully into s/tube and coupler. Make sure the s/tube is angled a little at prop. Make sure there's space at prop of 3mm. Prop that size needs a big esc and a good size lipo of 35C rating and a motor to handle. I'll get out of here before I get SHOT! Now all my boats get the same setups and stuffing tube extends 13% with front edge of rudder is across from drive dog. I'm gone!!!!!!!!______________________________________ _________ Post #13 YES, now a little down angle with a drill bit, not much.

[ray schrauwen]

If you need any more of those Dumas dog bones or brass parts, I've got lots collecting dust.

[siberianhusky]

Solid shafts were thoroughly tested and vetted wayyyyy back when, was all we used back in the late 70 and into the 80's when I first started running rc boats. Then flexes were "discovered", solid shafts disappeared for the most part very shortly afterwards. They did hang on longer with the rigger crowd.
Doesn't vintage 1/10 hydro require a solid shaft? Or is it any shaft as long as it is straight with the prop behind the transom?
I used to run an Aeromarine Scorpion with a K&B 7.5cc solid shaft with two sets of U-joints sub surface drive, then changed it to surface drive with flex, whole new ballgame! For a season nobody in the club could catch that boat. Not because I was better than the others, the sub surface drive boats were just that much slower.
Anybody remember Octura Strudders, Hum-dinger motor mounts? How abou Kool Klamps?

[knotsofast]

Climbing the Flex shaft learning curve

First off, I did see a significant increase in performance/handling with the stinger coming straight out of the transom. The boat rode flatter and the stern did not keep hopping out of the water like it did previously with the angled down solid shaft. But first time I really punched the throttle the shaft came loose from the motor coupler. I knew I had to leave some slack for the shaft to wind up, but I thought a shaft diameter gap was excessive, so I did half that. Well, it seems you need all of a diameter and maybe a little more. Then I noticed after my second time out, the gap seemed to disappear after running. My question: do the flex cables have to be broken in and the gap readjusted after the first few runs? Will the cables hold their shortened lengths after a break in period? Or is adjustment and re-adjustment a part of flex cable maintenance? And how the heck can you even have a discussion of thrust washers when the cables expand and contract so much that adjusting to run tight against a washer would mean you had to know exactly how much your cable would contract under max thrust to just meet the washer?

Thanks for all your help so far. I've got 3 more boats I'm building, but want to keep from making the same mistakes on all of them. So I'm going to try to get this one dialed in and figured out before putting the finishing touches on the rest.

Just one more question: Now that I am using flex cables, I have the option to use struts. I have one on my geico17 project and the hydro I'm building, but I don't really see the need on my monohulls. Angle can be adjusted by bending and gluing, and height is pretty much max that will still give the prop enough bite and does not seem to need constant adjusting, or am I wrong as many times before?

[boilo56]

If you want to go solid, i would suggest something similar to the traxxas Blast boat driveline design, with a u-joint before the prop shaft.http://s4.photobucket.com/user/Gophe...4046f.jpg.html

[iop65]

i'm not going much further into this but when you talk about solid shafts and i see what pictures show up and suggestions that are made: sure that you think flex is always the way to go ......

[tlandauer]

First off, I did see a significant increase in performance/handling with the stinger coming straight out of the transom. The boat rode flatter and the stern did not keep hopping out of the water like it did previously with the angled down solid shaft. But first time I really punched the throttle the shaft came loose from the motor coupler. I knew I had to leave some slack for the shaft to wind up, but I thought a shaft diameter gap was excessive, so I did half that. Well, it seems you need all of a diameter and maybe a little more. Then I noticed after my second time out, the gap seemed to disappear after running. My question: do the flex cables have to be broken in and the gap readjusted after the first few runs? Will the cables hold their shortened lengths after a break in period? Or is adjustment and re-adjustment a part of flex cable maintenance? And how the heck can you even have a discussion of thrust washers when the cables expand and contract so much that adjusting to run tight against a washer would mean you had to know exactly how much your cable would contract under max thrust to just meet the washer?

Thanks for all your help so far. I've got 3 more boats I'm building, but want to keep from making the same mistakes on all of them. So I'm going to try to get this one dialed in and figured out before putting the finishing touches on the rest.

Just one more question: Now that I am using flex cables, I have the option to use struts. I have one on my geico17 project and the hydro I'm building, but I don't really see the need on my monohulls. Angle can be adjusted by bending and gluing, and height is pretty much max that will still give the prop enough bite and does not seem to need constant adjusting, or am I wrong as many times before?

Unless you happen to have the worst quality flex cable, the winding up ( tightening up/shortening) of the cable will not be that obvious. You will not see a deformation after the run. The steel wire strand is made of high quality steel that will retain its shape.
What are you using??
A collet or a coupler??
What you are seeing/experiencing is that you have not managed to tighten your collet ALL THE WAY. If you are using a coupler, then the grub screw is NOT BITING the cable 100%. I favor collet, so let's talk about the collet scenario: It is probably the metal galling and friction that prevents that, and your good mechanical senses told you to stop the tightenng before anything breaks. After your second run, it was not loose enough for the cable to turn free inside your collet, but the PUSHING FORCE generated from your prop GRADUALLY PUSHED the cable all the way into your collet.
One trick I learned from Fuild is to use Anti Seize Compound. This can be bought from any auto parts store.

http://www.permatex.com/products-2/product-categories/lubricants/specialty-lubricants-anti-seize/permatex-anti-seize-lubricant-detail

Dab a bit on the prongs and the threaded area, you will be amazed to see how much further you can turn the collet .
As for the coupler, it is a dangerous contraption, the grub screw can flatten the cable or simply strip, it is better to get a QUALITY collet.

[knotsofast]

Thanks for the info tlandauer. I am sorry for my bad terminology. I am using Octura Electric Flex Hex's "for connecting electric motor shaft to flex cable." The package does not call it a collet or coupler, just Flex Hex. All my collets and cables and associated parts are Octura form OSE. You are absolutely correct. The cable did not permanently shrink, but my drive dog slid in and eliminated the gap, as evidenced by the scratch marks on the drive shaft. I need to tighten everything up better and maybe use some locktite. And yes, my collet was not as tight as it should have been, and the cable may have also slid in some there also.
I am actually testing 2 boats, the white 22 inch and a slightly narrower 23 inch monohull, both called DeltaForce, purchased from OSE. I have heard the dreaded "wheeeeeee" of the motor free wheeling on both boats while open water testing. At first I blamed it on loose fittings, then shrinking flex shaft, now back to mostly loose fittings. Not sure how much the flex shafts will shorten under max power. I have read in the forum that it happens and you need to allow a shaft diameter gap between drive dog and stuffing tube or strut to allow for it. If you don't have any freeplay a shortening shaft could theoretically pull the collet off the motor shaft if its way out at the end as on my 23 inch Delta.