Aft mainsheet boom attachment

[ngeo]

Dear Forum Members,

I am owning a Topaz Magno dinghy that I'd like to modify from center mainsheet to aft one. My inspiration came from a youtube video featuring the same boat (

).
I did small research on the topic and found that RS200 is having the same boom as Magno but with aft mainsheet attachment ( same as on the youtube video). I have attached the diagram from RS but I struggle to get where exactly the holes shall be drilled and mounted. Therefor I hope owners of RS200 to share some close up photos of this attachment or point me out where to get more deatiled info how to DIY it on my own boom.

 

[wet feet]

First a word of caution-if you may ever race you boat,will this modification be permitted?Next point,while you may use the RS200 for inspiration you don't have to copy it in every detail if all you are seeking is a system that better suits your needs.I would suggest that the simplest solution may be to get hold of one of these and slightly modify the shape of it,then use monel pop rivets and zinc chromate paste (or similar) to attach it to the boom.Duralac would be good if you can find it locally.



Boom Strap https://www.tridentuk.com/gb/product-boom-strap-al-a4216.html

 

[ngeo]

First a word of caution-if you may ever race you boat,will this modification be permitted?Next point,while you may use the RS200 for inspiration you don't have to copy it in every detail if all you are seeking is a system that better suits your needs.I would suggest that the simplest solution may be to get hold of one of these and slightly modify the shape of it,then use monel pop rivets and zinc chromate paste (or similar) to attach it to the boom.Duralac would be good if you can find it locally.



Boom Strap https://www.tridentuk.com/gb/product-boom-strap-al-a4216.html

Thanks for your suggestion Wet Feet, I thought of it too but end of the boom is already occupied by the selden's outboard boom end and then this boom strap has to sit in front(side) of it or re-rivet it on top of seldens.
This boat is not to be raced ( I don't even know if there is Magno class , seems not a popular boat ) and it used as educational tool only.
What I find appealing in the selden's system is that maybe they've tested in enough to be sure that it a good compromise oveall and since I also want to have the mainsheet running inside the boom, selden solution provides this high-enough position for the end block.
I've attached a close up on the selden's outboard boom end.

 

[wet feet]

Running the mainsheet inside the boom only really works if you can take it out somewhere near the gooseneck and then lead it aft.there is no fitting that I know of which will allow relatively low friction and still permit the mainsheet to exit the boom near the middle of the boat.The articulation or alignment just isn't possible in the space.It is much less challenging to use the fitting I suggested earlier and to use the fabric tunnel that the RS200 uses to lead to a mid boom attachment point for a block.There is an alternative that also comes from Trident.

Dinghy Sheet Boom Sling https://www.tridentuk.com/gb/dinghy-sheet-boom-sling.html

 

[ngeo]

Running the mainsheet inside the boom only really works if you can take it out somewhere near the gooseneck and then lead it aft.there is no fitting that I know of which will allow relatively low friction and still permit the mainsheet to exit the boom near the middle of the boat.The articulation or alignment just isn't possible in the space.It is much less challenging to use the fitting I suggested earlier and to use the fabric tunnel that the RS200 uses to lead to a mid boom attachment point for a block.There is an alternative that also comes from Trident.

Dinghy Sheet Boom Sling https://www.tridentuk.com/gb/dinghy-sheet-boom-sling.html

You are completely right: it is challenging, but somehow doable as shown on the video ( but sure, there may be problems with this setup that are not obvious from the video ). The selden boom mod.2628 already has opennings on the bottom for the outhaul and quick reef. I did not experienced so far any chafe on the outhaul line but I am not trimming it as often as mainsheet and rope dia on the main is twice as big...
Boom sling is go to solution for main lead aft and I can see it on RS200 but honestly I am not that thrilled by the aestetics of it and I am willing to experiment.

 

[ngeo]

Seems that Streaker Class has some allowance for in-boom mainsheet (https://www.streaker-class.org.uk/downloads/Rules and Forms/Streaker Class Rules Sept 2016.pdf):

8.19. A slot may be cut underneath the boom to allow the mainsheet to exit from inside. The slot is to
be a maximum of 250mm long

 

[ngeo]

Just found this -> Spinnakers Without Tears & Split Mainsheets: Solved https://www.roostersailing.com/blogs/boat-maintenance-tips/spinnakers-without-tears-split-mainsheets-solved

Seems like yet-another-diy solution, but since it is comming from Rooster, might be a legitmate one.

 

[gggGuest]

Its not the boom I would be worrying about so much as the hull side. The Magno is roto moulded boat and not over stiff. Are you going to get enough strength in it?

Do you really need to go into all the complication of an in boom mainsheet? I've used both, but now prefer to run the mainsheet under the boom so I can sheet directly from the boom. In any case its all easier and simpler that way. All you need to stop the mainsheet strangling you on gybes is a simple sailcloth sleeve round the boom with the mainsheet running through.

 

[ngeo]

Its not the boom I would be worrying about so much as the hull side. The Magno is roto moulded boat and not over stiff. Are you going to get enough strength in it?

Do you really need to go into all the complication of an in boom mainsheet? I've used both, but now prefer to run the mainsheet under the boom so I can sheet directly from the boom. In any case its all easier and simpler that way. All you need to stop the mainsheet strangling you on gybes is a simple sailcloth sleeve round the boom with the mainsheet running through.

Well, hull is LDPE which is indeed very flexible but since it is able to hold the pull from the shrouds it will be OK but only using specific attachments. I really do not need all the complications of in-boom mainsheet but I am just curious to give it a try.
I have enough clues already from the Rooster photo above how the U bolt shall be mounted but still it'll be better if there are RS200 owners willing to share how it is done there.