Andrew
Can you post a picture or two? Enough to show all the sheeting. I’m wondering if you are sheeting in too tight and that is causing the servo hum? The sheet should have a little slack when fully in. How far out on the boom is your sheet attached? How long is your servo arm?
Try this. Disconnect the sheets from the booms. With the booms full out measure between the sheet attachment on the boom to the fairlead(or sheeting post). Compare this to the amount of sheet travel. Report back here.
Don
Now I’ll go back and read the entire post to see if I’m up to snuff.
I can visualize your system. It is quite conventional. As long as everything stays in line through the servo travel, there should not be excessive friction in your setup. Just try the manual pull test to see if you can feel anything excessive.
If not that then I think we are back to an electrical issue.
If you can remove the winch easily, then you can bench test the servo using the RX and battery and wiring harness to see what weight it can dead lift. Then try again with another wiring harness and battery.
If you have the same type of servo in your other boat, can you swap the servos to see if the problem stays with the boat or moves with the servo?
OK
You said earlier that you have 180 degrees of rotation. You also have a 5" arm with a block. From one extreme to the other you have 10" of arm travel, double this because of the block equals 20" of sheet travel. A typical IOM setup only needs about 10 to 14 inches of travel(the boom to sheeting post measurement). This might explain the servo hum. With a 5" arm you could almost go without the block. Figure out the amount of travel you need and adjust your arm length accordingly. A 6" arm would be best but I doubt there’s room in the boat. My guess would be around a 3" arm with a block.
Don
I would say you have zeroed in on the problem with the 5" arm. The sails have too much leverage at that length would be my guess. With an 815 using its full travel you should be at 4" or even slightly less to get all the travel you need on an IOM.
It sounds like your wiring and power source are all very correct so I would place it all at the available torque. I’m not sure if the torque loss versus arm length is linear or not but an inch extra is a 25% reduction or so. And that would be the difference between working or not. I’ve put 815s in quite a few boats and not seen the servo unable to pull in the sails.
Hopefully here is a picture of an 815 in a Kite. Ignore the extra lines that appear but that was a great idea that didn’t work out. If the picture doesn’t attach I’ll send it to you off line.
Barry, and others I was wrong,
My arm length is 3.5" I guess I had not had my coffee this morning and just guessed. The servo does not have a problem puling in the sails at all, I just have to head up to take some pressure off of them. Barry your picture looks like my set up. I also thought about putting som elastic o the inside as a booster? I will post pics soon.
It looks quite good I would say. I have a question but it has no experience of technical backing. The pulley you use on the arm is relatively large compared to what I am used to using. I can’t imagine it has much effect if any on the effort required but that’s about all I’ve got left to ask. Is the pulley diameter affecting its ability to pull the sails in? It is providing some offset to the line as you pull in, effectively making the arm length slightly longer and when it is offset I wonder if that causes some kind of odd loading. Pretty weak point I will admit but the best I’ve got at this point.
The whole boat looks pretty good. You should come to Saltspring next June!!!
Barry,
You might have somthing with the pully and off set? I will check. Earlier I did say I got 180 in travel and that is only when I use the fine tune on the side. The pulley wheel is from the local hardware store used as a wheel for a sliding screen door. I also use one for the turning block at the back of the boat. Saltspring? I do not think i would be able to make it but what are the dates?
I can’t see anything obvious either. I would think that the larger block would be easier to turn, assuming nice free bearings. I think Barry is right about the size of the wheel changing the mechanical advantage but it would only be by 1/2 the diameter of the wheel which still keeps the arm length about 4" which should be fine. Maybe what we’re seeing here is a difference in opinion about “light” winds. I’ve been to Alberta.;);)
Sorry, you’ll have to bring the boat to Saltspring and we’ll try and sort you out then, unless of course you’re beating us, then you’re on your own.
Don
Don,
Light winds I mean coasting with A rig. So if your guys boats are on a run wing ong wing will you 815 pull your sails in while the boat is still on a run? and till what time? top end of A rig?
So maybe to answer my question I will ask more questions. Don Saltspring would be fun, but there are no long weekends in June so it makes it tough to get there.
Barry could answer that better than me as I don’t use an 815 yet but one of my friends has a boat that is rigged same as yours and I’m sure he has no trouble sheeting in.(He wins consistantly) It just doesn’t seem right that yours has trouble.
The humming servo bothers me most. Does it do it all the time? Close hauled? Any clues might help.
Don
The Canadian National Class Championship Regatta is the first weekend in June. Lots of good boats and good skippers will be there so it is a great time to see a variety of boats and rig setups. You learn more in one of these weekends than you do from months of club sailing.
It is almost like there is too much tension or friction somewhere. I assume theh pulleys rotate quite freely as the line goes over them under load. If they don’t rotate freely under load then there will be a lot of line friction because the line is one quite a bit of surface area on pulleys that size. If they don’t rotate freely then you are trying to drag the line across the pulley surface.
This servo easily pulls the sails in on a run in order to gybe. That is one of the big advantages (once you practice it). It is so fast that the momentum of the booms snaps them across ona gybe without having to bear off much to make it happen.
The constant chattering makes me thing there is an induced load in the sheeting system somewhere. I can’t give you a number to reference but if you pull on the sheet line up near the servo you should be able to pull the line, and booms in with little effort. The rubber band thing should be set so there is just enough tension on the line, with the sails fully out, to keep the sheet line on the pulley(s). The rubber band also has to be long enough to have enough stretch to handle the sheet travell distance without getting too loaded up. I’ll try to find a picture of one of teh boats showing the elastic layout. If yours is too short you will load the heck out of the servo.
Barry and Don, I will look into the pully binding, it is just a plastic wheel over a aluminum bushing so it might be binding, As for the chattering it is mostly during close hauled condition even with the arm in line with its exit point? I guess this will be one of my winter projects. There is going to be a local sailor (not RC yet) on Saltspring this weekend so treat him well and make sure you send him home with a boat or two. He is staying with Martin H.
Sometimes just a click or two of trim will put the servo in a place where it isn’t hunting.
To follow up on the elastic bit, I have attached a photo. This is a boat that we are just starting to rig out and it has an arm winch in it as well. The yellow line is the sheet and the orange/red stuff is the elastic. Yours may be like that but I couldn’t tell from the pictures.
If you ever get a chance to come this way for any reason, let us know and we’ll make sure you get a sailing in. You don’t need to bring a boat just your thumbs.
I will bring my thumbs when I can, I promise. I checked the back wheel on the boat and it was stiff so I drilled it out should work better, I hope. Will try on the weekend if we do not get snow. Yes snow laugh all you want at least it is a dry cold! hahahahahah
I think I would try to make a trip to Fabricland, or whatever a good material source is in Calgary and go to the Notions department to get some elastic cord. They usually have some different sizes so get the smallest they have and give that a try.
I would think that the tension in the retractor might be too much and that there is a good chance the string on it might bind on itself while it wraps on and off the pulley. I use one of those on my belt to hold the hex driver that fits all teh adjustments on my boat and I’m pretty sure that is a lot stronger than you want for the sheet tension function.
I just looked up to make sure there were Fabricland’s in Calgary and I see 4 listed. The stuff is usually available with a black or white outside cover. The smallest stuff is likely 1/8 or less in diameter.
Barry, I will try fabricland and see what I can find. The retreaver I use is not that strong? But as stated before i am in Alberta and we might not think things are as strong as we think. I find it has a constant pull, where elastic would have no pull at the start then get more as it pulls ?
Actually I think you would find that your retractor is loading up the more it is pulled. It is winding a spring up so it pretty much has to increase tension.
With the sails all the way out you only want to have enough tension to keep the primary sheet on the pulleys.
These are just little boats so they don’t need super strength in many places.
If you can’t find the elastic (I think you will) let me know and I’ll get some here and send it to you.
Barry,
Sailed boat today after fixing wheel to move easier, this help a little. When I got home I thought about what you said about the retractor vs. bungy, so I disconnected the retractor all together, held the boat with the nose down and tried to pull in sails? The sails did move in but not very easily? What am I missing here? I even disconnected main sheet, then jib sheet and there was not much difference. It seams that when the servo arm is 90degrees to the sheet that is the most resistance but once it is has gone past there it move quicker?
Andrew
