Leech teltales on IMF?

[flightlead404]

I have a new main on a Selden IMF rig. It came with 3 telltales on the port side, that's it. lol Not even matching telltales on the starboard side.

But 2-3 telltales on the leech would be most helpful. Last time I tried stick-on ones on the prior sail they lasted about 3 (un)furling events.

Any recommendations for putting some leech telltales on an IMF setup?

[caradow]

Probably useless.
However where the telltales that came on the sail along the luff or leech?

Just shape the sail while watching your knotmeter (not GPS) and learn what is a fast shape.

If you want a mainsail you can tweek get one that has real shape in the leech.
Unfortunately that doesn't exist in the IMF world.

Mainsails can also be adjusted with variable luff tensions which you can't do with roller furling.
Good starting settings for a main is around 55% max. cord depth then as wind gets stronger by increasing your luff tension you move that forward and the sail becomes more forgiving and in turn helps you get thru the waves. With a draft aft sail (>55%) your light air speed will improve.

The only real setting you have on a IMF boat is in the foot which is not as important. It is helpful if it is tighter upwind and downwind you can ease the outhaul.

IMF sails are pretty much bedsheets.

But on the brightside you have a boat with effortless handling.
Anyway much more enjoyment in sailing other than watching telltales on a main.

[wingssail]

Originally Posted by flightlead404

I have a new main on a Selden IMF rig. It came with 3 telltales on the port side, that's it. lol Not even matching telltales on the starboard side.

But 2-3 telltales on the leech would be most helpful. Last time I tried stick-on ones on the prior sail they lasted about 3 (un)furling events.

Any recommendations for putting some leech telltales on an IMF setup?

Use yarns, sewed onto the leech, not that it will do a heck of a lot of good, but you want them to fly if you're going to get anything out of that roachless main. If you sheet in too hard they will wrap around the back of the leech and that will indicate that your main is stalling, ease it out

[flightlead404]

Originally Posted by caradow

Probably useless.
However where the telltales that came on the sail along the luff or leech?

Just shape the sail while watching your knotmeter (not GPS) and learn what is a fast shape.

If you want a mainsail you can tweek get one that has real shape in the leech.
Unfortunately that doesn't exist in the IMF world.

Mainsails can also be adjusted with variable luff tensions which you can't do with roller furling.
Good starting settings for a main is around 55% max. cord depth then as wind gets stronger by increasing your luff tension you move that forward and the sail becomes more forgiving and in turn helps you get thru the waves. With a draft aft sail (>55%) your light air speed will improve.

The only real setting you have on a IMF boat is in the foot which is not as important. It is helpful if it is tighter upwind and downwind you can ease the outhaul.

IMF sails are pretty much bedsheets.

But on the brightside you have a boat with effortless handling.
Anyway much more enjoyment in sailing other than watching telltales on a main.

That's just not true. There is *some* luff tensioning ability, albeit no Cunningham or downhaul.

There is tension on the foot as you mention, via outhaul.

Importantly there's also leech tension, twist, which is controllable via main sheet and vang.

There's adjustment, although not as much as a traditional main I would agree.

Leech telltales can give some insight into the flow of air across the sail.

The telltales that came on it are three on the port side in a horizontal line about half way up from the luff to about halfway across the sail at that point.

[flightlead404]

Originally Posted by wingssail

Use yarns, sewed onto the leech, not that it will do a heck of a lot of good, but you want them to fly if you're going to get anything out of that roachless main. If you sheet in too hard they will wrap around the back of the leech and that will indicate that your main is stalling, ease it out

Thanks for validating they will be of some use.

The question was really, what are the recommendations for material and attachment mechanism, and will they last beyond a handful of (un)furling?

I was actually thinking of taking some nylon ribbon, maybe 1/4" or 5/8" and stitching to the leech at the 1/4, 1/2, and 3/4 points.

If they are going to come off in a weekend its not worth the effort however.

[caradow]

Originally Posted by flightlead404

That's just not true. There is *some* luff tensioning ability, albeit no Cunningham or downhaul.

There is tension on the foot as you mention, via outhaul.

Importantly there's also leech tension, twist, which is controllable via main sheet and vang.

There's adjustment, although not as much as a traditional main I would agree.

Leech telltales can give some insight into the flow of air across the sail.

The telltales that came on it are three on the port side in a horizontal line about half way up from the luff to about halfway across the sail at that point.

Sorry if I offended you.
I probably should not have said anything.

The problem is using a mainsail without a proper roach tremendously limits the sail to be trimmed where it makes a "significant" difference in speed other than what you achieve with mainsheet tension alone. Even outhaul adjustment in those sails makes little difference because in actually that difference is down low around the foot which is the most insignificant part of a mainsail.

My criticism comes from the fact that I come from 35+ years of competitive racing both at the National and World level but now also have a boat with IMF and I can honestly say I hate it.
However sew on your leech telltales and go for it.
Good luck and again my apologies for the drift.

[flightlead404]

Originally Posted by caradow

Sorry if I offended you.
I probably should not have said anything.

The problem is using a mainsail without a proper roach tremendously limits the sail to be trimmed where it makes a "significant" difference in speed other than what you achieve with mainsheet tension alone. Even outhaul adjustment in those sails makes little difference because in actually that difference is down low around the foot which is the most insignificant part of a mainsail.

My criticism comes from the fact that I come from 35+ years of competitive racing both at the National and World level but now also have a boat with IMF and I can honestly say I hate it.
However sew on your leech telltales and go for it.
Good luck and again my apologies for the drift.

No offense taken. However you spoke in absolutes, which many do on here, and the absolutes aren't true.

No, IMF isn't ideal, yes IMF is much less tunable and much less of an ideal shape (among other issues), and yes I'd have preferred a traditional main. Unfortunately beggars can't be choosers so I'm dealing with it.

Unfortunately on a fractional rig my main is my "engine" and I need to get the max performance from it, IMF or not.

[JPA Cate]

Hi, flightlead404,

We for years (with dacron sails) used red yarn and a sail needle to make tell tales. You thread the needle with the yarn, and pull the yarn through, then knot it on both sides of the sail. If you have laminate sails, then I would make my own telltales. Use a big bit of sticky back sail mending cloth, about the size of a US 50 cent piece, and make your nylon ribbon about 1/4" wide. You will have to rely on the stickiness of the sticky back cloth, because you would not want to pierce a laminate and allow moisture in. Clean the area carefully with acetone (dacron) or alcohol (laminates) to make sure there's no salt or dirt on the place you stick it. Cleaning before sticking really works a lot better. I think they'll stay quite well -- we've had them go 4-5 yrs.

Ann