Increasing boom length and mainsail area

Discussion in 'Sailboats' started by Tony-Pion 30, Sep 2, 2009.

  1. Tony-Pion 30
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    Tony-Pion 30 Junior Member

    I am currently undertaking a complete refit of my Van de Stadt Pion 30 and am considering installing a longer boom and larger main sail so that I can install a new 'maxi' type (Lewmar terminology) traveller system aft of the cockpit. This will allow me to run the mainsheet to winches mounted on the cockpit coamings adjacent the helm for short handed sailling.

    I am interested in comments about the effect of increasing the area of the mainsail from 20sqm to 25sqm and increasing the foot of the mainsail from 3.10m to 4.0m. I am particularly interested in the impact this will have on the ballance of the boat under sail with the movement of the centre of effort from the rig further aft.

    The current rig is a reasonably high aspect ratio of P=10.5m and E=3.10m.

    The keel is a swept back fin and is currently off the boat. I am prepared to modify the keel if necessary to account for any shift in centre of effort from the rig.

    The boat is currently very well mannered on all points of sail.
     
  2. alan white
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    alan white Senior Member

    Much depends on the hull and the rig type, but no matter what, the boat will exhibit a stronger weather helm to a greaster or lesser degree.
    I'm curious why you'd make such a drastic change in order to relocate the mainsheet further aft. That's a lot of money and in the end you may have more weather helm than you bargained for.
    I'd rethink the whole idea and look at some alternatives.
    Do you have some pictures of the boat, especially the cockpit?
     
  3. Ramona
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    Ramona Senior Member

    Tony,
    I have just done something similar to My quarter tonner, Miller and Whitworth 26 designed by Ben Lexcen. Its a typical early 70's IOR boat with small main and large genoas. I used a Hobie 16 mast cut down as the boom and I have cut down a sail from a 30 footer to suit. I have just got to finish off hand sewing sail slugs to the full length batten pockets and its all set to go.

    The reason I altered the sail plan is lee helm. I had lee helm in light breezes and it becomes neutral with about 18 to 20 knots. I sail single handed nearly all the time and having lee helm coming out of a tack is a real pain. I tried raking the mast back but still no weather helm. My new boom is 3.3 metres versus 2.8 and the new sail is Flatter with 3 full length battens. This will hopefully give me weather helm which will help sailing up wind and coming out of tacks, also safer.
    If you have weather helm now in manageable amounts then adding more main may be a problem when you bear away off wind. The extra boom could also touch the water reaching and downwind. Your keel is cast iron too, how do you plan to alter that?
     
  4. alan white
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    alan white Senior Member

    Why not just add more length to the boom and be done with it?
     
  5. Paul B

    Paul B Previous Member

    Back in the 1980s and early 1990s it was very common to increase the E of old IOR boats without any other modifications. We would go up to +20% in some cases with good results.

    The boats sailed better on all points of sail. The amount the total Center of Lift moves is insignificant, so no need to move or modify the keel in most instances.

    Your boat seems to be of the early IOR type sailplan, so it should be OK for you to try. Your idea to add 30% might be a bit much, although the resulting aspect ratio of 2.6 would still be pretty good.

    My own non-IOR type boat has had the boom extended from 11.5 feet in increments to the current 13.5 feet with no issues.
     
  6. Tony-Pion 30
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    Tony-Pion 30 Junior Member

    Alan,

    The picture looks a little more like this. The Pion 30's were built to Lloyds A100 and mine has no history of osmosis. The boat is currently in my back yard drying out and undergoing a total refit to the point that it has been completely gutted inside and the keel has been removed. I will be installing new wheel steering and have already taken delivery of 13 new Lewmar portlights and hatches.

    This refit gives me the opportunity to recinfigure the standing and running rigging to suit my intended application of short handed day sailing, cruising with crew with the occasional 'around the cans' and Hamiton Island Race Week.

    Time and labour are in plentiful supply and the purchase price gives a reasonable leway for expendature. I am thououghly enjoying the refit journey and hope that when it is finished it will be perfect.

    I would like to relocate the traveller aft of the cockpit to relocate the stresses and allow to open up the keyhole companionway by installing a companionway hatch. This also allows for a better short handed setup. It will also give me the opportuniy to run all lines aft to the cockpit.

    I have attached Pion 30 drawings from the Pion 30 web site and a photo of mine. you will notice that the Australian built Pions have a different coachhouse.
     

    Attached Files:

  7. Tony-Pion 30
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    Tony-Pion 30 Junior Member

    Ramona,

    Love to hear how it performs when you get it finished.
     
  8. Tony-Pion 30
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    Tony-Pion 30 Junior Member

    Paul,

    Thanks for your comments. I will take you suggestion on board to limit the extension of the foot which is in keeping with what Alan has suggested about extending the boom only. If I needed to modify the keel I would infill to void above the aft rake with steel plate and fair it. The keel prpofile is similar to a bulb so the upper section is only approximately 75mm thick so moving the thicker part of the keel aft with this should not bo too much of a concern. It will also locate the greatest lift from the keel higher up.
     
  9. Tony-Pion 30
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    Tony-Pion 30 Junior Member

    Alan,

    The only objection I have to extending the boom without extending the foot of the sail with it is a consmetic one. However there is always room for compromise. Perhaps I could paint the end of the boom black to try to conceal it??
     
  10. alan white
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    alan white Senior Member

    Sounds like fun alright. I don't know enough about the boat to comment intelligently, but good luck with the changes. Keep trying here and you'll eventually get someone to talk to who has the same boat. I owned a Carter 33 but unfortunately sold it before getting a chance to recommision.
     
  11. Tony-Pion 30
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    Tony-Pion 30 Junior Member

    Alan,

    Thanks for your input. You will see my requests for information from time to time along with my contributions where I feel I have enough knowlege to contribute. It gives me a buzz being able to discuss issues that I am passionate about with someone on the other side of the world. Gotta love the internet.
     
  12. alan white
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    alan white Senior Member

    I figured it was an aesthetic thing. I don't think there's anything you can do to hide it. Let form follow function.
     
  13. Gilbert
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    Gilbert Senior Member

    Unless you can keep the boom from lifting, depending on its length it could get hung up on the backstay.
     
  14. Munter
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    Munter Amateur

    We extended the boom on our old Cole 43 because the original sailplan design was optimised for a certain rule type (RORC?) and the boat appeared under-canvassed compared to more modern designs. Like your application a longer boom gave better sheeting angles given the original location of the traveller. We didn't notice much change in the helm though this was on a mast-head rigged boat so our changes would represent a smaller change in the scheme of things compared to the changes you are proposing to your fractional rig.
     

  15. alan white
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    alan white Senior Member

    Though the foretriangle area appearss at least equal to his main's area. There are a few options if the helm does get a mite hard-mouthed. One is to rake the mast forward. Another is to add a bit of area to the keel's trailing edge. Finally, a short bowsprit (maybe 12"-18") is a very useful cruising feature. It won't need a bobstay if the underside is gusseted solidly to the stem, it gets the anchore roller out further, and shouldn't affect the existing headsails too much in terms of sheeting angles. I'd actually like the look if the gusset was straight and not clipper-shaped.
    This all potentially increases the working sailplan modestly.
     
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