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Mast bend - Dream On previously Dump Truck
I have one of the original race sails that came with my RL24 used in the 89-90 nationals. This sail in top condition (fully batt. Kevlar) so I am using it when racing and am learning how to trim it. It has a lot of roach (goes with blade like jib) and generally goes well up to 18 or so knots controlled by traveller/main sheet but not much vang (Vang downsized by Prev. owner). There is a magic box for adjusting the forestay tension and mast prebend bend. Above 15-18 knots, I find it very hard to flatten the sail fully through the entire length of the leech (i.e. all leach streamers flying or just breaking). It takes constant tweaking with main tension and traveller position. The mast has been sleeved 1m above the shrouds at some time to repair a broken mast. I am thinking of fitting a backstay to give more control over the mast bend. I observed how easy it was to bend the mast when the boom tent was supported by the main halyard and this seams a possible easy fix. Should I up the vang power? Another option short of replacing with a new mast could be a 16'skiff mast. I have located one that may suit only it has a fibreglass-tapered tip. Dose the rl24 class allow this and is this a direction that may be worth exploring? It is budget wise compared to new mast/sails option and I would learn heaps.
Garry Carr21-Oct-2005    Edit    Delete 
Re: Mast bend - Dream On previously Dump Truck
Garry

Dump truck was originally fitted out with a 'Coxon rig' and it would appear from the info you have supplied that it is still the same rig. Was your damaged mast made by Pelgreen?

I suggest you contact North sails Sydney and ask them for a copy of the rig dimensions and their tuning and sail trim sheet for the Coxon rig. Way back in the early eighties Mike Coxon was keen on having no back stay with a small amount of overlap in the jib.

I think the sleeving repair would have changed the bend chararistics of your mast and I would be for buying a new mast section and swapping the fittings over. I think I have a 20 to 1 purchase on my forestay but I remember that I had to strengthen and stiffen up various parts of the hull to take the extra loadings.

I think there is a set of the current class rules in the other RL 24 web site.


Regards

Alastair
Alastair Russell22-Oct-2005    Edit    Delete 
Re: Mast bend - Dream On previously Dump Truck
I have a Mk4 with a similar rig to yours.

I only use the yacht for cruising hence I opted to put the racing set of sails away and use an old sail set up with battens and reefing points.

When I first sailed INMA with the full battened mainsail I was more than impressed with her ability to sail with the roachy mainsail and flexible rig. I have seen 10 -12knots boat speed effortlessly in 20 knot winds on reaches and downwind with 3 aboard.

Having sailed other yachts with fractional rigs and backstays I was not prepared for the way the Peelgrain rig has the tip fall off dumping wind up high in the gusts.

Other yachts I sailed used the vang to heavily control sail twist hence the sail shape stayed where we set it. INMA's rig bent effectively flattening and depowering the rig through the gusts.

As for dumptruck's tuning, the only advise I can give is leave the vang very light and work on shifting the traveller to get variable twist as the mast bends.

The sleave in the mast may stiffen the section that was repaired. If it is an issue I suggest getting a sailmaker to come for a sail and trim/maintain the sail. The tuning of sail to rig is best done by a sail maker, even if you have to pay to get him on the yacht. The sail maker can look at the battens and batten tensin at the same time, its all part of the package, battens have come a long way in 15 years.

As for using 16 foot masts they are legal and very suitable for RL24s that are racing. Generally the 16 footer mast and sails are bought together because the combination is the feature that provides the improvement. Putting your old RL24 sail on a 16 footer mast would be an unknown quantity, it might or might not work.

While planing I have had the engine drop that increases the drag and load on the sails. When it drops the steering goes sluggish and the boat gets tender (predicably). Make sure you minimise drag in heavy conditions. For the record I have the outboard tilted in the open well, it worked fine.

Don't forget to adjust the outhaul and cunningham as the wind pressure increases. I also find oversheeting the jib and reducing the slot makes the boat tender in high winds. INMA is definitely different to other yachts I have sailed with fractional rigs. For what its worth it took me several attempts and a bit of luck before I figured out what worked with the flexible rig.
Greg 22-Oct-2005    Edit    Delete 
Re: Mast bend - Dream On previously Dump Truck
My recollection is that the rig used in 1990 on Dump Truck was in fact a development of the standard skiff rig, with a slightly larger mainsail and smaller jib. It performed very well in the flat water of Lake Cootharaba that year.

My father has a similar configuration and uses a fibreglass tip. One thing I would check, though, is the position of the forestay attachment. It is higher on the skiffs in relation to the shrouds and I am not sure whether it should befor RLs. I suspect not. A call to a sailmaker stressing that you are looking to depower up top in gusts should answer that.
James Shannon23-Oct-2005    Edit    Delete 
Re: Mast bend - Dream On previously Dump Truck
James is correct about the position of the forestay bridle on the RL24 Mk4 rig.

INMA's rig has the shrouds extending above the forestay bridle. With the adjustable shroud tension on INMA as the shrouds are hauled backand down the increased tension bends the mast due to the extra compression on the swept back spreaders and the moment created between the shroud and the forestay. This mast bend flattens the center section of the mainsail. The moment by the forestay and shrouds causes the whole lower section of the mast to bend further than if the shrouds and spreaders were at the same hieght.

The tapered top section of the mast bends in higher winds allowing the top of the sail to fall off and flatten in gusts dropping wind and reducing forces up high. When I get it working correctly the rig adjusts itself through the gusts.

INMA (RL343) is in a photo on this site with Kandyman (RL508) on Lake Cootharaba, INMA is coming second.

There is an excellent explanation of flexible rigs at
http://www.bethwaite.com/10167,02,2-0-automatic-rig---part-1.html
http://www.bethwaite.com/10264,02,2-0-automatic-rig---part-2.html

INMA was rigged by the chandler at Lake Cootharaba in the late 80s, I suspect the RL sailers were well ahead of their time with many of their developments.

Greg
Greg 25-Oct-2005    Edit    Delete 
Re: Mast bend - Dream On previously Dump Truck


Greg

I looked at the photo you mentioned and I see what you mean about the smaller blade jib. I also see that it is blowing hard and that the boats have another jib track set further aft for a bigger jib for use in the lighter wind strengths! You will note that one boat has a reef in the main.

In 1983 Dump Truck won 7 straight races at the national titles in Queensland with her set up. Three of the top 4 boats had coxon rigs then as had the two top boats at last years titles.

I totally agree with you on using the vang in conjunction with the traveller to creat twist and allow the dumping of the top of the main. Is there any other way?

The problem with the tapered alloy masts way back then was that the veeing out of the section and the subsequent welding created temper and bend consistency problems. Aluminium work hardens so quickly after coming out of the heat treatment oven! I believe the breakthrough came with introduction of the uniquely Australian manufacturing process used in producing the spunspar mast. Their method overcame all the weld and production problems of the past.
Alastair Russell26-Oct-2005    Edit    Delete 
Re: Mast bend - Dream On previously Dump Truck
Geez your eyes are good for a middle aged bloke, Alistair:)

I think, though, that the second track, visible on Kandyman, is a curved track for the vang, rather than a second jib track.

I believe, also, that the set of sails being used on Dump Truck now and in 1990 are different in measurement to those used by Peter Yeomans in 1983. My recollection is that the owner in 1990, whose name escapes me, had opted for a larger main and a smaller jib, useful in inland waters and downwind, but can be costly in bigger seas.
James Shannon26-Oct-2005    Edit    Delete 
Re: Jib Overlap on Dump Truck
James

You are right,I used a larger magnifying glass on my right and good eye and it appears that I have taken a halyard turning block on the cabin top as a jib track. I see what you mean with regard to the boom vang track.

I remember Mike Coxon telling me that they had carried out high level research in a wind tunnel on the relationship between jib and main. He said on the rl24 you must have a small amount of jib overlap and that the foot of the jib must be close to the deck and the fairlead close to sail. Just look at the latest Americas Cup boats of today they just look like an enlarged RL 24,s of twenty years ago (The fast ones anyway)!!! This is all highly classified stuff I do not want you to tell Bernie!~!!
Alastair Russell27-Oct-2005    Edit    Delete 
Re: Mast bend - Dream On previously Dump Truck
Alastair, your comments on the jib overlap and keeping the fairlead close to the sail is very interesting.

Over the last 2 years I have been playing with my cruising rig finding how to trim it for best performance close hauled. Last trip on Lake King we found ourselves crossing Lake King close hauled in 10-15 knot winds and my jib trim (pretty much as you described it) amazed me on the way INMA remained powerd up on very tight angles to the wind. If you saw my cruising main sail you would understand my amazement.

I was considering raising the tack of the jib to play with twist, after your comments I suspect I should be happy with what I had.

Not bad fun for a cruiser out for a days sail close hauled at better than 6 knots with the bimini up and the partner enjoying playing with the trim of the jib.

Greg
Greg 27-Oct-2005    Edit    Delete 

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