Days 279 Boom reorganising, Anchor rode splicing, new GPS, evening sailig

Boom

Reef blocks and winches installation design

As you remember I made 4 reefs on my new main sail, and 4-th i would likely never use ;)

I tried to calculate what could be loads in reef lines on my boat and get really surprised numbers.

My sail:

Configuration	Luff remaining	Estimated area	Full-sail area
Full sail	11.14 m	25.60 m²	100%
Reef 1	9.45 m	19.2 m²	75%
Reef 2	7.80 m	13.6 m²	53%
Reef 3	6.13 m	8.8 m²	34%
Reef 4	4.46 m	4.9 m²	19%

At fourth reef set, about 4.9 m² of mainsail remains exposed to the wind.

At a worst-case wind speed of 60 knots, that sail area produces approximately 3.7 kN force.

If about 40% reaches the reef clew, the clew must take 1.5 kN. Because the two reef-line legs pull at a shallow angle of about 10°, each leg carries approximately (1.5 ÷ [2 × \sin(10°)] = 4.3) kN. Allowing a 50% increase for gusts, flogging and shock x1.5 = 6.4 kN. so, a reef block i need for about 8 kN working load.

The same logic calculation gives us about the same loads on all reefs.

Reef	Sail area	Maximum wind	Total sail force	Normal line tension	Peak line tension
Reef 1	19.2 m²	20 kn	1.62 kN	1.86 kN	2.80 kN
Reef 2	13.6 m²	30 kn	2.58 kN	2.97 kN	4.45 kN
Reef 3	8.8 m²	40 kn	2.97 kN	3.42 kN	5.13 kN
Reef 4	4.9 m²	60 kn	3.72 kN	4.29 kN	6.43 kN

6kN if about 350lb, no way to pull it by hands, so I need to have winches to be able to set right tension.

BUT, with reasonable use winch must not exceed MWL for lines and construction.

so, I selected #10 winches with "reasonable high" cranking force person may do is 70lb with x10 advantage 700lb. So, we good here.

Next challenge - curvature of the boom. I would need curvature following spacers to install the blocks and winches.

So far I am looking to use 3D printed ASA plastic with 100% infill to make them. 3D-printed ASA spacers is what I can match the boom’s curvature instead of trying to force a flat block onto a curved surface. With 100% infill and about 2,400 mm² of support area, even approximately 12 kN of total screw-clamping force creates only around 5 MPa of average pressure. ASA can comfortably support this.
From inside, washers would concentrate the load around four small spots risk of make dents local cracking. The full size backing plate ties all four M5 screws together and spreads the pulling and twisting forces across the complete mounting area.

Plastic also has some plasticity and able to form better connection between spacer and boom surface.

In short words.

I install blocks and winches to the mast using 3D printed spacers to follow boom curvature and distribute load. ASA plastic calculated like good enough material for this. Back side is I will need to make sure i will retight screws several times after installation.

Spacers for the block.

External

One side of the spacer is flat, other following boom surface. Also spacer is asimetrical to install one block 10mm higher than boom equator and other 10mm lower to let reef lines closer to boom end go freely without touching other reef block.

Internal

from inside the boob another spacer installed to align backing plate be in parallel with the block.

Backing plates are 3mm SS304 flat steel with tapered holes. center hole is to put screw to keep plate on the spacer.

Winch spacers.

External.

Internal

Backing plates are 5mm SS. small screws keep plate at place.

Boom disassembly process

In dreams all looks well ontill some stuburn screw appeared to stuck.

I think engineers who use slotted round-head screws in places where they can seize have a special place in hell.

Disassembling was relatively simple with help of impact screwdriver, BUT one from 20 screws made me more problems than all other together!

After several times screw bit jumped out of screw and scratchcard my hands I realized why you will not find slot screwdriver bits for impact screwdriver. They just jump out and injury your hands.

What i did - I put a nut with hole a size of screw head diameter. and tie it to boom with duct tape!

then easy undo this screw without any risk on screwdriver jump out of slot.

Bastard in hands.

Boom is stripped.

Reason why i stripped it is simple - I need to put backing plates inside the boom and screws sticking inside are not helping any.

Blocks installation.

Drill holes

Put external spacer and use it as template to drill holes

Backing plate

Use hot glue gun to glue backing plate to wood slat, then route tiny steel rope th

Then use this steel ripe to pull backing plate to close enough to align screw holes and put screws.

When holes aligned - drill a small hole (only in aluminum) on the center, countersink it and put small screw to keep backing block on place.

Apply tefgel on the screw and aluminum holes and install the block! is it look nice?

Then two winches

Backing plates, same approach.

Dryfit before put the winch, then winch at place

Boom coning back.

Starboard side Reef1 and Reef3 (reef1 block I left original)

Port side Reef2 and Reef4 blocks, outhaul line on the top.

Winch and cleat for reefs on the each side on the boom.

One more GPS

Installed 10Hz GPS mostly for autopilot for gps mode. higher frequency GPS let autopilot work with better accuracy.

Nothing fancy, just standard UBlox 10 module, but I made custom outdoor enclosure for it to mount on back rail.

Anchor rode

It is very interesting, there a lot of double braid anchor ropes, but how people splice them to chains to let it go thru the windlass. just doing eye splice is not working connecting point appears too big and too stiff to go thru gypsy. My solution is to upbraid core and cover (keep plaints intact) and re-braid plaints it in 8 plaints rope ( core is 8 plaints originally). Then do 8 plaints rope to chain splicing.

Probably it is temporary solution, but look not so bad.