Crafting Mast Step for Outrigger

Bob the mast is a colossal lever. Just for fun, imagine the sail CE be 10 feet above deck. Let the submerged part of the mast be two feet. Now you have a lever with a 5 to 1 ratio. The deck is the pivot point of the lever. The heel of the mast will develop a powerful force, likely ripping the bottom out unless there are load transfer bulkheads and plenty of reinforcement for the heel location. If the sail developed a modest force of 100 pounds in any direction, there will be 500 pounds of force exerted at the mast heel and 1000 pounds of force at the deck plate.

That is not all. The hull will twist with all that torsion load. Whether or not the Hobie hull is up to that abuse will be resolved when you try it. Not an adventure to be trifled with. A free standing mast or even a wired one, can be dangerous if its support system fails. Ask me how I know this.

Do what needs to be done for the sake of safety and hull survival . Take the deck off the hull. Install at least three or four carefully fitted and spaced bulkheads whose load is spread to the hull with plenty of tabbing. At the mast heel, make a short, well fitted, keelson that is capable of spreading the load for a foot or two. The mast heel will rest on that part. Put the deck back on. Go sailing, have fun, live long.

 

Messabout, thanks.

I have resigned my self that the deck needs to be removed to do it right.

I guess my stays-fix needs me to remove and redo the internal step anyway.

I had the lever idea in mind from past experience and why I decided to go at it last.

I also figured the greatest stress would be on a windy port tack, when the ama had no where to go but down, sorta. And was thinking of the original MO design.

Sadly, for me, that is a job that needs more time and time is about done in Minnesota, so I packed it in until April next. Spent yesterday packing/marking boxes and laying hulls down for travel.

I will have the winter to plan and set a work schedule. Dang it! But I do have another boat to sail and the grouse season is open, so I have immediate alternatives.

R and R the deck to do step, fun! I take it off, might just go with MO plans but crafted to handle round stubby and spread the stress as far as practical.

I get a brainstorm, will bring it to your attention here. You never know.

Seems to fit, son named the boat "Aboat Time!" How prescient.

Thanks for helping me avoid an avoidable disaster.

 

Later I will scan in pix of the Malibu Outrigger step plans. Substantial.

But, I had thoughts about carbon alternative, keeping in mind my intent was/is to recycle the hulls and not make project difficult to keep a safe RM factor. got to be a way using carbon tube and cloth, without ripping off whole deck and rebuilding hull inside out.

A Remove deck area only at step to beef up step with carbon and connect to carbon stringers running length of hull along keel line and at deck hull joint stem to stern connecting every meter or so.

B. Beef up deck and form exterior step and add stays, but I believe the interior as above would still be needed...large and variable righting moment to match.

Was using this link http://www.liveantares.com/pdf/RefMastLoad.pdf

but edited to fit "3-factor."

and Eric Sponberg's and Petros' observations http://www.boatdesign.net/forums/sailboats/rotating-free-standing-mast-design-35484.html .

 

Have you thought through the ultimate goal for the problem?

The mast produces a big bending moment. Let talk about the side to side moment first. This big force becomes a torque load that must carried to the cross beams. These are the structures that resist rolling.

If you could build a "torque tube" that would insert inside the hull and provide solid attachment at both the mast and cross beams, you could minimize carrying substantial torque loads through the hull itself. If you do want to use buildup on the inside the hull to carry the torque, you will need much less buildup with at least a portion of the fibers oriented at 45° to the length of the hull.

Just remember that all of your torque loads require the structure from the mast to the cross beams.

In addition, do not forget the fore-aft bending moment. You can put a lot of force on the mast when tightly sheeting for an upwind run. Edit: I see you plan on having a forestay to take care of this concnern

 

Thanks Mr. Flados, I am late to this as did not receive note you responded, sorry.

To be candid, had not gone that far yet. Just rationalizing change in plans. My mental picture sort of like a stick embedded in slightly smaller sized brick, re stresses, with brick being boat hull.

Below is pic of orig mast step in MO plan and was my original guide. Step is substantial wood and typical failures hitting beach too hard, back in the day, were fractured stubbies, not in hull or step.

The stem ref in the plans refers is to flat front of MO bow, as built to accept lighter shaped balsa or pine bow attached later...

Too, I had originally planned to alter cut deck open aft of dagger board slop as foot rest/small cockpit, so this may make that work but earlier rather than later. I can visualize that as part of the structure or system.

I am neither engineer nor math guy, now mostly opinion writer, so you have idea. Been building or rebuilding boats since the late 60s, but never messed with mast steps from scratch and powerful rigs like MO. My 110 and Ensign were a world apart.

I have not done calcs as I lack the skill and maybe have alternative that will fit stayed or unstayed stubby Malibu Outrigger's semi crab claw rig.

Something s[inning in head about using full-length carbon stringers at upper deck seam and carbon tube and cloth along keel line, as hull bottom is rounded, connected all ways, with idea that entire hull is involved...like the orig MO. But, trying to do so any backyard butcher can copy to salvage old hulls like these.

Am sucking it all up, nevertheless, and appreciate the help. Obviously, I know squat and working to fix.

To be clear, crossbeams = akas hull to hull, or deck interior deck beams or supports inside the hull? The stubby mast is to be stepped on or in the main hull.

 

Where the front cross beam originally connected to your hull is probably some amount of stout structure (or at least thicker glass) inside the hull. This is the obbious place to connect into.

 

Yes, I see. That juncture is aft of mast just in front of hull balance point and is now more substantial with added carbon/epoxy needed to accommodate horizontal akas. I can see a internal skeletal carbon plan to spread out the stresses.

 

Internal carbon from the mast step back to the beam location is can add a lot of strength. However, glass may actually be a better choice. The existing material is glass. If you go with carbon, it will be more "stiff" that the underlying layer and will not work with the underlying layer as well as just adding more glass.

Regdarless of material, a single thin flat layer does not carry torque. Build up all ID surfaces (including the corners between surfaces) with fibers oriented at 45° to hull center-line and you can carry a lot of torque with a minimum buildup.

I would apply buildup first and would extend the buildup to well past the two endpoints (mast step, cross beam).

Think of how thin tube is stiff in torsion as compared to a C section or a flat strip.

 

I agree. I looked at the beam areas from inside and Hobie seems to not have done much, maybe one layer extra of roving.

Am thinking on it a lot, in fact was just perusing available carbon tapes and comparing to glass for similar reasons and cost.

I found comment on this site by Eric Sponberg on another topic, who suggests the best layup is a balanced one in layers and materials. Makes good sense to me as does your idea too.

Only reason I was thinking carbon rods or tubes was light and stiffness relative to torque levels as righting moment rises and distributing it as much as possible.

Lots of stuff going though my head. I might take a trip over to U here and ask, if I can get to the prof who teaches in their composite school.

I really think removing entire deck is a mistake but the way Hobie joined them is so uneven I have not decided.

I have also considered epoxying 6 inch wide carbon tape to interior hull floor, followed with cut strips of epoxied Doug-fur, with some carbon tow between each strip.

The strips would run length along each side of the smoothish and round keel interior (round bottom) to emulate the stringers in the original Malibu outrigger plans, with tabbing every meter or so to outer hull...(created by solid spots in hull along length by drilling small hole and removing the fill and refilling with an epoxy bog of sorts, and then tabbing the strip ends to the carbon mast step base (installed), stern, and maybe to the stem forward a couple feet of step.

Have to contend with dagger board slot in place too. Might be excellent anchor point to strengthen instead of going to transom...?

Then maybe, between the tabbed areas, run smallish carbon rods or tubes up along sides and under deck to other side, tabbed to deck...like interior of WWII B-17, to give mental picture.

Madness, I know. Just trying to fit to task and keep simple so not hard to replicate, if others dare similar outrigger projects...

As things have it, I knew in back of head the step would be central and save halyard and main sheet, all sits ready for install---in spring---I get this right and finished. Looks like no Everglades Challenge this spring, sadly, unless I find a warm place to work around here...by some miracle.

 

Well, I might have a plan. I am having a fellow here rip two 2x4x9 long Douglas fir into 1/16-inch strips, if I do not go with shrouds.

Plan to epoxy two 2x2 sections of the strips with strips of carbon tow between each strip, clamped...and while wet, tape to one side of hull from dagger case to the step to match hull shape.

And use strip of s-glass along keel-line and will fasten the strips through hull every meter or so and also tab it to a stringer extending from each side of the dagger case. Will run similar shorter version from step to bow also.

May add vertical s-glass at anchor points also.

Each of the four strips will be anchored to the step using 3/8 dowels.

Not much weight added, decent stiffness and length to spread out the stresses.

The carbon covered sections of the step itself will need to be screwed in place (screws make it easy to replace if needed).

But, as I have been advised, shrouds are easier and likely safer.

Any comments etc will be welcome. I figure I have invested too much time in this project etc, to let it go...not to mention the T-6 tubes etc. If I hit upon a winter work place, will jump on it and proceed...but small town and not much available but will ask around. You never know.

 

As if I had enough to sweat, garage door cable let go...two weeks wait for door and the weather warms...stuck inside and boat was trussed down for storage. Might have to re-hang hull and do some work.

At this point going to do Flados's idea with Chris Ostlind's help as well. Schedule is planned as follows:

Remove deck over step to give working room.

Remove clay I used as dam for epoxy glass step base.

Run foot-wide, 45-degree biaxial glass strip stem to stern and combine with some sort of way as structure with the foot well below.

Drill step fore/aft to accept two each, carbon rods tabbed to the stem glass.

Add wood or carbon stinger/bulkheads where deck and hull join and connect each side across beam.

Add step base and attach each section with screws for easily removal if needed later.

Add foundation for Hexaratchet mainsheet cleat etc on deck.

Add self draining foot-well anchored to prepared bulkheads from above not sure how to construct but will work it out, as long as I am messing with interior and was planned anyway.

Replace removed deck section.

Add "chainplates" for 5/32 shrouds (2) from stubby mast (plus forestay) anchored to either vaka (main) hull or foreward, using Hobie anchor pins and/or NACRA castings and swaged eyes to Hobie pins, using adjustable links to either deck edge or forward aka.


Sound like a plan? If so, give weather god a nudge and ask her to make it a quick winter, you have connection!

I might, not decided, add minor carbon rod-set across hull at each aka connection point, at dagger case to strengthen those areas a bit.

Local (carbon engineering student) suggested I go with stations in orig plans (Malibu Outrigger) as carbon and tie to added glass along keel and the strips. Might be simple way to spread the pressure along entire hull.

Voila!

 

After some consideration and frustration (garage door cable snapped and have been trapped until fixed...waiting for parts in small town) I concluded the fore/aft stiffness would be increased by the akas or beams in place but also adding the below...

Remove deck over maststep area to afford more work space to create decent step foundation.

Add foot-wide strip of glass inside hull, down stem or keel line to stern.

At three points between bow and stern, craft carbon "stations" (1 at step, 1 at forward aka or beam and one just aft of dagger slot and be sure each "station" includes being tabbed to deck.)

Connect the "stations to the center glass by tabbing to carbon tube running fore/aft.
(Idea is stiffen hull and spread out the righting moment level.)

Remove meter of deck aft of dagger slot for self draining footwell cockpit and tie all to hull and keel.

Carefully replace forward deck section with added carbon to hold and wedge when stepped.

Of course, the stubby will be supported by shrouds anchored to forward beam with forestay.

When weather warms again, will begin and post progress here...or earlier, I get lucky and find warmish work spot that has power.

 

As promised...I came on to thank people for helping and add to this thread...what has transpired...

Mast step to be like a trailer ball mount...why I had not thought of that???

Anyway, instead of complicated step I have already more or less crafted...wood cut and carboned...

Will make a wider base to support a 2" ss ball, which I plan to fit into female (is that PC?) molded socket inside stubby base...with stays...simple, fast...and cheap.

Pics when weather permits...heat wave and snow near gone. But March can be a killer here.

Minnesota, snowless while the East shovels...who'd a thunk it?

 

Well, as time passes, we get things done and should report...

Major deviations...shrouds and forestay, instead of planned unstayed stubby.

Added carbon stiffening in main hull

Full mast step all T6 from base to above deck (have not figured out cover for when on trailer.)

Also dumped the gas power for electric...all up 400 lbs needs not much push and the elec troller motor no stink, easy to raise etc ...

Here are prelim pics...not wet for day or so. Waiting on one job and have to add hook and loop luff to sail...will add more pics later. Last pic is plan at this point...so far it is close.

Rudder assy not on yet, might need to extend tiller and extension, motor mount for stern elec trolling motor still under advisement and tramp is in mail...

Should be wet in day...have to be certain it floats...and sailing within the week (how many times I thought that and...)! Re orig rig plan, save shrouds and fore stay, fairly close...

An adventure...

 

What I ended up doing is set stays up to support the stubby, which is stepped in circular AL section in hull, on the advice received. The stays take pressure off the foam Hobie hull and works fine so far.

Will post detailed pics from other computer later.

Sorry it took so long, but the process here took longer than expected...