I’m currently building a Graupner Saphir and have a few sail rigging questions I was thinking of adding an adjustable outhaul to the main and a jib lifting line on the jib boom, has anyone experimented with lowering the booms closer to the deck or making the boom height adjustable? My sailing experience is not from the RC world but from sailing dinghies which have more adjustments to shape the sails.
I was thinking about making the main boom/ gooseneck assemble adjustable on the mast to raise and lower the boom off the deck this was a good option when sailing dinghies but I don’t see it on RC sailboat builds, is this a worth while modification?
Is there a formula or a certain distance that a ridged boomvang should be installed below the main boom gooseneck on the mast?
Is jib boom lifting a useful modification?
The jib boom pivot point currently attaches to the deck with string, will a ridged pivot point work, does it need to be flexible?
There are some folks who run deck sweeper and inverted solid vangs on some boats. I know my victoria has an inverted vang, but its not as slammed to the deck as it could be…
there is no set formula for were the vang attaches, all depends on how much leverage you need. the closer teh vang attachment is to the main gooseneck you end not not pulling down as much on the main…less of an angle.
a job boom topping lift is a nice addition as it allows you to put some twist in the jib.
A topping lift on the jib boom is almost a necessity on model boats!
The height of the booms is going to be different in the model boat world, because you have no ballast to move, to help keep the boat upright. When the boat heels, either the jib boom, main boom, or both, may touch the water, trimming the sails in and making the boat head up. If you are trying to head downwind, you are SOL! Raise the booms a bit, and you may get overpowered earlier. A difficult trade off!
Also, most classes have height limits on the mast, and you only get a little room to play with rig height. My suggestion is to copy the fast guys, and do little modifications at a time, towards what you think is better. If you start off radically different, you will not know what to change if your boat is slower!
If you want to delve into the technical aspects of the sail rig, check out Lester Gilbert’s site at http://onemetre.net There is enough info there to make your head spin.
Thanks for your input guy’s It’s amazing when you start reading about sailing and rigging how technical it can be, I got the ridged boomvang built tonight I think it will do the job. I was reading a site for big boats about vangs and they recommended they be mounted at 45 deg. no less than 30 deg. and the mount on the boom should be about 1/3 the length of the boom from the gooseneck, there is no way I can get that angle even with the boom at the stock height. I have checked out Lester Gilbert’s site some really good info. a lot of it is way over my head I’ll wait for the Crib Notes. Here is a link to my building log if you want to check out what I’ve done so far.
New question - Should the main boom and jib boom line up with each other at the same height off the deck? I thought I read somewhere that for the sails to work together and perform properly both booms need to be at the same level.
Not really they were a pain in the a$$, very time consuming, thanks for your help I’m starting to get the sails up I’ll ad some more pics in a few days.
I’ve been doing some reading on rigging and sail trim could you guys check me to see if I have this right.
Jib boom counter weight – helps the boom to achieve a balanced swing and counters the aft of the pivot weight of the boom and sail.
Topping lift – in light air this takes the tension off of the leech by raising the boom aft of the pivot to help shape the sail which creates sail twist.
Jib halyard – shapes the luff of the jib and would need to be adjusted according to weather and if the jib stay tension changes.
Now the questions
What exactly does adjusting the jib stay do, it aspires to me it would change the angle of the jib boom from horizontal and would be adjusted in opposition to the topping lift, or is this something which is adjusted and left alone or do you adjust this according to wind conditions?
Could you use a ridged boom vang to push up on the main sail boom to take the tension off of the leech helping to shape the sail in light air or does the vang only pull down on the boom to flatten the sail?
If the answer to # 2 is yes could you use a ridged pivot post to attach the jib boom to the deck and a ridged boom vang to the jib boom to push the jib boom up to shape the jib in place of a topping lift, would you ever want to flatten out a jib like you would the main in heavy air?
The jib forstay on a RC sail boat will add tension to the leech as well as tension on the luff. this keeps the luff from knuckling under when you are in a blow. if you add toping lift tension to loosen the leech this adds forestay tension.
I have solid vangs on all my boats. this way you can dial in main twist plus it also gives you the advantage of not encountering any “sheet vang” Ie when you sheet the main in all the way with a non-solid vang you will pull twist out of the sail…
What you are talking about on the jib is a radial jib fitting. I have I have toyed with a simple version on my Victoria. the problem with my radial jib fittings is that you need to have a lot of forestay tension to keep the forstay from knuckling. but there are others with don’t need the extra tension but cost $$$ do a search for radial jib fitting
Thanks Marc, do you have any pic’s of the set-up on your Victoria? what do you mean by keeping the forstay from knuckling? I added some more pic’s to my Building log.
I do not have any pics here at work…here is a link to what I was doing…http://www.rcsailing.net/forum1/showthread.php?5310-radial-jib-fitting. I’ll take a pic at home and post later…mildly impressed the boat points great and does really well in light air, but in heavy air not as good… I haven’t figured out why…
probably the loose nut between the ears…
have to remember the your sail is a wing and the forstay with your jib luff surrounds is the leading edge of that wing. if that leading edge of the wing is not firm enough it will knuckle or try to fold over on it self. stalling the sail
Nice buildlog, I still got wood for the turnbuckles…
Perhaps it the shapely curvy silhouette so tall and slender giving the appearance of being in tone and firm yet knowing that the aluminum is so soft and supple…
used a ballbearing fishing swivel, solid aluminum, some carbon, and some ball joints…
Fwiw I’m going to redo it and make a “light air rig” super light, and with Orcon as the sail material…Slam it all to the deck. the boat has gotten a bit piggy with the jib fitting and the ball bearing goose neck i’m several ounces over class min
Thanks for the pic’s I started on one last night I’ll post some pic’s when it’s finished I don’t know how well any of these mod’s will work till I get the boat in the water. I’m leaving a lot of the scale accessories included in the kit off so that should help make up the weight difference for all the stuff I’m adding , I think it still might float ! I noticed your Victoria has only one stay up front does the jibstay act as a forestay or is a forestay not needed on that rig ? My Saphir has both a forestay and a jibstay.
all of my boats, from my footy to my ec 12 have the forstay in the luff pocket on the jib I do have a jib halyard for adjusting the luff tension independent of the forestay…
I can’t currently find where I found the information, but an experiment was carried out to answer your question in principal. They used an IOM in a wind tunnel with the jib set as low as possible and then withe the jib set as high as possible. From memory - the outcome was that the sails were 15% more efficient with the jib set low. When I track down the site again I will post the link.
The jibstay acts as the forestay. The sail material isn’t sufficant to support the luff of the sail so either you will need to ‘hank’ on the jib to the forestay or incorporate the stay into the luff, which is the best option. If you have both you will never be able to get enough tension into the luff of the sail to prevent it sagging off too much when the wind picks up a bit.