Hello all

I have an idea that may just be original. If not could you please tell me your experience with this concept.

The design uses a standard drum servo and two pulleys on either side foward of it. The lines go out of the servo drum either side to the two pulleys then back past the drum and out to the yards.

The pulleys are attached to a swivelling wooden or metalbar that can pivot back and fourth probably 30-40 degrees . This pivoting bar is attached to another drum servo that is free wheeling , via a line that wraps around and attaches to the ends of the bar. The freewheeling drum is then attached to the servo drum and derives it's power and pull from it. Diameter would obviously need to be worked out with this.

When the servo is pulling in one brace it drives the other drum in such a way that it swivels the opposite side of the bar away thus increasing the distance of the slack side to the servo drum and vice versa. Does this make sense?

As mentioned I don't know if this is a new idea. I'm trying to find what could possibly be wrong with it (maybe it might just work, I don't know?)

would greatly appreciate feedback

David H

David, looks like it should work, it also looks like a difficult way to do the same thing you can do with a swing arm servo
John R.

thanks john,

I have 2 big drum servos and want to use them rather than getting two arm servos. I would like to crack this problem, I'm just surprised more people have not commented. There seems to be a fair amount of time and investigation going on into solving the slack problem with drums. If this helps and takes the art one step further , than great.

I just need to hear from people who have worked with drums to see if this really is viable

regarts

David H

Hi David,

I'm not sure if I am seeing this right, but do you think that the drive from the servo-powered drum to the free-wheeling one should be crossed over (each drum moving in opposite directions) ? That way you would provide more slack to the "non-tensioned" brace (by moving its pulley further forward) & less to the "tensioned brace" by moving its pulley back ?

The "gear ratio" between the 2 drums would have to be quite large to allow for the servo drum to make 4 or 5 turns & then have the free-wheeling drum only make 1/4 of a turn.

Brilliant idea - still trying to get my head around it ! Looks like it might be a very elegant solution to the problem of tacking jibs - slacking off the leeward sheet before hauling in the other side.

Just had a thought - I was looking at it from a jib crossover point of view - providing slack, instead of a brace point of view - taking up slack.

Could work for either ! - Nice.

Thanks & Kind Regards,

Peter D.

Thanks peter,

Agreed the ratio between the servo drum and the freewheeling drum on the other side would be quite large. Initially I though that the servo drum would be pencil diametre or a little larger to make the freewheeling drum move a quarter of a rev.

Anyway, I was just driving down the F3 to sydney when I had another idea this morning. You could probably dispense with the outer free wheeling drum and simply use two pulleys mounted on small sliders mounted onto a rail either side of servo.

Each of these sliders is attached to each other using a simple line that goes around a pulley mounted at the far end of the slider. This line attaches both sliders , so as one pulls in tension towards the servo it pulls the slack side away from the servo.

Being linear in movement should mean that you will get more travel away from the drum servo for the side that is slack. The unit is simply driven by the side that is in tension. The original arm idea being radial in movement would not give as much movement away from the servo as a linear one could. I'm using big drum servos so I don't think overloading is going to be a problem.

I don't know if this has been done before, if so someone please say so and give me feed back, does this system look like working? I don't think it will eliminate all the slack but it may greatly reduce it. worth a try?

regards,
David H

That last one looks like it ends up being an over engineered version of simple springs - like I'm using in Constellation.

Maintaining tension isn't difficult to set-up, especially in larger models using rubber, springs, weights, or cones (Jarvis winch), A little slack won't hurt anything so long as you consider it in your set-up - running things so that slack isn't a potential problem.

On the real boats, the hands on the cast-off braces let them run. One person will be there to watch for snags, and then take up slack and belay when each yard is set. To replicate that you need the off-side winch to be free-wheeling with a little friction to let the braces out - then you need it to become rigid when its it's turn to haul braces in.

What you want is something like this YouTube thing, but that reverses the "rigid" and "sprung" drums when bracing the other way.

Homer Bracing Winch (1 min 22 sec)

All that is multiplied where you're controlling multiple yards per mast. They each have their own geometry, and the larger the model, the more yards should be actively controlled - course and tops'l yards at the very least.

Hey guys! Been traveling - just home and saw this.
If starting from scratch, I believe a very good (robust and simple) design is to use a spring-loaded sliding servo.
Worked very well on a board mock-up. I was planning to re-engineer Syren, but to make room for the slide travel would require a major demolition of the existing mechanicals.
Here are reference posts:

http://www.rcgroups.com/forums/showp...&postcount=131

http://www.rcgroups.com/forums/showp...&postcount=139

http://www.rcgroups.com/forums/showp...&postcount=142

http://www.rcgroups.com/forums/showp...&postcount=144

In response to the idea of reversing the fixed and sprung drums on my proposed system I think you could do this with two servos and sprague overrunning clutches. Each drum would get its own servo and each drum would have a one way clutch. that way when the common alxe shaft was powered in one direction one drum would lock and the other would free wheel.

I haven't actually tried this, but it might be a solution to a more rigid system and I believe would allow the use of less spring tension.

Vince Homer

Another thought. I think one could also "stack" the drums putting several on each side on a common axle. They would be of different diameter determined by the yard length with connecting springs between each drum.. That way you could brace all the yards on a mast at once with two servos.

Vince Homer

Pondsailor and others now building SC&H brigs have asked about rigging material. I twisted all mine on a ropewalk, but then learned of an excellent commercial - and super-cheap - source: memphis Net and Twine.
Check out the following two posts I made earlier covering the source, sizing for different scales, etc.

http://www.rcgroups.com/forums/showp...&postcount=109

http://www.rcgroups.com/forums/showp...&postcount=110

Also, teh PDF showing the sizes of twine available and the scale sizing.

Just re-checked Memphis Net & Twine website. They now have even more sizes and types available. To get all the sizes you need for a SC&H 1/24 model would cost a lot simply because there is so much in one of their spools and so many sizes are needed if you want prototypical sizing.
If enough interest, I will buy a complete selection of needed sizes for 1/24th scale rigging, in white and tarred (very dk. brown like the prototype) and sell "cuts" (maybe 10yd/10meter increments) as needed for the models. I'll dye the white line with acrylic waterproof/fadeproof ink to a light tan if wanted. Method works very well.
Pricing TBD, but need to cover dyeing cost, time, leftovers, bad orders, postage, etc. - but I'll try to keep it reasonable.
If interest, let me know how much you might want. I'll try to list soon all the diameters I used on Syren and in what locations.
Note - this is twisted line, like the prototype, not braided line as in the kit. This twisted nylon bonded line has very low stretch and excellent appearance - no fuzz, etc. It's used by museum ship modelers.

Have been asked about the external "drive pods"
Some detail in this old post, and some pictures too.

http://www.rcgroups.com/forums/showp...&postcount=747

The latest, final design was simple - PVC pipe endcaps were epoxied over the two ends of the motor. One cap sealed the open end of the motor. The other cap was drilled for a model submarine shaft seal. The wires were passed through a hole in the endcap and also sealed with epoxy.
No water gets to the motor.
The motors I used were from a surplus store. They are made by Faulhaber. Dimensions approx. 25mmD x 50mmL. They are sealed motors and run with very low current (they are high efficiency).

Here is the Faulhaber motor product page:
http://www.faulhaber.com/servlet/com...66/i86089.html

The drive shaft seals are from a RC submarine parts supplier:
Mikes' Subworks.
http://www.mikessubworks.com/page1.html

Pics of 32 pounder carronade on Brig Niagara, an accurate replication of a brig from the War of 1812. It's a working carronade.
Also pics of a 1/12 scale model I built from the pics and measurements when onboard Niagara.
Short clip of the model carronade firing its black powder charge.

The clip:

carronade clip (0 min 7 sec)

Hal,
See your e-mail.
Cheers,
Dan

Is there a cart for inline launching that has been figured out? I have been looking but I am sure I missed it.

here's what I am needing. If I get a box trailer I can see a problem with the side cart. I know a few have talked about getting a extension ladder and putting two wheels on it so that you can pull it out of a box trailer and then roll it to the water and then extend ladder to launch boat into lake. I can do this with an aluminum ladder and about $40.00 in large plastic cart wheel. As in all things I dont want to reinvent something that has been posted.

My plan is to be able to set sail with my boat without needing a second guy. I have a 12' x 7' trailer in mind that is 7 1/2 feet tall. If this works as I hope I can see loading Surprise into trailer on my own. Secure it, and get to lake. Pull out cart with boat on it, attach wheels (1 to 2 min) and then head to water, launch it and stow ladder. Then reverse and go home. If I can do this I can have boat rigged most of the time and come and go any time of the week without finding a buddy to just pick up one end for a few seconds. I was looking at getting a wheel chair crane and swinging it from current cradle to cart, and this is very doable, just would take a little longer for the transfer.

So any ideas before I get to far ahead of myself?



I found this setup on another forum, it handles getting into and out of box trailer but still needs work on getting in and out of water.

Thanks

Gary