I could use some advice/suggestions/guidance. I made the slotted mast tube in the hull so that I could adjust the fore/aft position of the mast. How often do you actually make that adjustment with a 10R? How fine do the adjustments need to be? What is the simplest mechanism for making such an adjustment?

Edited November 3Nov 3 by mdeleo

Once you've found a good position for each rig then I don't often move it. One way to adjust is to make up a set of blocks that fit in your tube (one at the top and one at the bottom) and then drill mast size holes in them in slightly different places - i.e. front to back. I made six blocks. 3 each with the holes extreme end, 1/4 and just under half. Reversing them gives you 6 vertical positions for both top and bottom. Using different positions top to bottom allows you to adjust the basic rake. If I need to fine tune the balance on the day then I do this by altering sail twist and /or sheeting angles.

10Rs aren't very sensitive as the long waterline means they tend to sail in a straight line anyway (unlike DF65s which are very sensitive). Hull shape and heel angle affect the balance. I designed my latest 10R to minimise the movement of both the centre of bouyancy and the centre of lateral resistance with heel and it seems fairly successful. I have an IOM that is an exteme skiff shape (about twice the beam of a modern design). This boat is a nightmare to balance as it goes from extreme lee helm in light winds to extreme weather helm in strong winds. On this one I do have to move the mast step around on the day.

Thanks John. Is there enough force from backstay tension to keep the mast butt forward in the slot so that I only need blocks in front of the mast and not behind ?

Edited November 4Nov 4 by mdeleo

Forestay strut and mainsheet post anchored into hull. Parts are from SAILSetc:

https://www.sailsetc2.com/index.php/fairlead.html
https://www.sailsetc2.com/index.php/tube-moulding-150.html
https://www.sailsetc2.com/index.php/sheet-post.html

Edited Thursday at 17:245 days by mdeleo

You will need to fix the bottom of the mast both fore and aft. A sideways slot in the bottom of the mast and a rack arrangement in the box is one way. The deck level only needs to be located in front of the mast - you could use a mast ram for this. Are you reinforcing the deck beteen the mast box / fin box and the shrouds? This is the most heavily loaded area of the boat (well that's what I think). I use a triangular structure made of 4mm square section carbon. My fin box / mast box is in one piece so I can get away with one brace. Your deck is much stiffer than mine so maybe you don't need it, but you will need to fix the top of the fin glove very securely to the deck.

4 minutes ago, John949 said:

You will need to fix the bottom of the mast both fore and aft. A sideways slot in the bottom of the mast and a rack arrangement in the box is one way. The deck level only needs to be located in front of the mast - you could use a mast ram for this. Are you reinforcing the deck beteen the mast box / fin box and the shrouds? This is the most heavily loaded area of the boat (well that's what I think). I use a triangular structure made of 4mm square section carbon. My fin box / mast box is in one piece so I can get away with one brace. Your deck is much stiffer than mine so maybe you don't need it, but you will need to fix the top of the fin glove very securely to the deck.

Thanks again for responding. Yes, that wide bulkhead that ties the mast tube into the sides of the hull is also connected to the deck which has a carbon/aircraft ply/carbon sandwich the full width of the hull. Fin box integration with the hull and mast still being sorted out.

Edited Thursday at 18:435 days by mdeleo

Compression strut added between the #1 bulkhead and the mast. Will also serve as an anchor for the jib sheet line.

Adding another bulkhead and aluminum strut for the backstay.

The deck will tie all of this into the hull.

Edited Saturday at 18:023 days by mdeleo