"Fowl Play" another LLM.

Hi, I've seen the questions on the forum and here are my findings. These may or may not suit, but they are aimed at large sails and big pilots in the 5.6mtr wheelbase of a Lake Lefroy Mini yacht.

I was going to redo these ages ago on "Google sketchup" to look nice and neat, but I could easily build 2 new yachts quicker.
My students at the Ag college and I are learning it, but it's not coming easily to someone who has spent his life building gear from a sketch off the back of an envelope.

Here is the layout of "Fowl Play" that I sail with a 6.2m2 and 6.9m2 sail, in almost all winds. Wind speed, needs to be above 25knots to downsize to 5.5m2. I weigh in at 113kg, and I'm 183cm tall.

These plans are the changes I have made to a standard "Lake Lefroy Mini" plan, to perform with larger sails.
A standard LLM built exactly to Paul Days plans, as on Seabreeze Forum,
www.seabreeze.com.au/forums/Land-Yacht-Sailing/Construction/Build-a-Landyacht-Lake-Lefroy-Mini-Yacht/
performs perfectly, with the smaller sails it was designed to use.
I just push the envelope of the design and have arrived at these measurements with "Fowl play" which is the 22nd LLMini I've built. So a fair bit of trial and error has evolved into these measurements.

All my chassis are from bent galvanized street signs I pick up from our local shire yard for free.

From the plans below, I have now gone to a mast step angle of only 2 degrees, adjustable back to 10 degrees and have not used the rear settings on the mast base. ie; mast in its fully forward position for all sailing.

Also the seat base/back intersection, has been moved 75mm ahead of the centre line of the 35mm x35mm x2mm RHS rear axle.

If I built another, I wouldn't bother with the complexity of the adjustable fore and aft mast position, I would just make it adjustable for rake angle (Like Pacific Magic in the construction section of Seabreeze).
www.seabreeze.com.au/Articles/Land%20Sailing/Original-Pacific-Magic-Plans-by-Paul-Day_1514690.aspx

I am using a 6.9 m2 cammed sail on a 5350mm extended carbon mast. IMCS 29 with 1000mm of 4.5mm walled internal stiffener up the bottom. The top 150mm of this stiffener, has fingers cut into it, to relieve the stress point, and bonded in with silicon.

Hope this is of some assistance for the bigger fellas out there.



Just ignore the shim note on the photo below, as it is for my fitting into my jig I have.





The ratchet block is just stored here so I don't lose it. I use a 6 to1, "Crocket downhaul" system.

12mm all thread does the adjusting.




My rear axles have only 1 degree of camber now. 0.7 before I am seated in it. This snap below is the view from the rear of the axle. My yachts have gone from 8 down to 5 degrees of camber. "Saline by" was down to 3 degrees and was holding better when I used a 5.5 m2 sail. "Landyacht" suggested I go a bit further and they are now 1 degree. This works a treat for my rig. Tyre wear is very even and the back end is nailed to where I want it. When it lets go now, the world spins round big time. Last time at Lake Lefroy on very hard salt, I ran the left side at 1 degree and the right at 3 degrees for a couple of hours, just to see if I could tell the difference. Yes that's why I was back and forth across the pond on the same track for so long. There was a marked difference in the tyre noise and the 1 degree wins hands down on grip and = better speed. I just kept standing the mast up till it cornered well and the back didn't slide at all. It was a great couple of days to test things out and I tried to get as many people sailing it, for their ideas as well. Most comments were that 6.9 m2 isn't at all different to the smaller rigs, even in high winds it's very manageable.


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Fowl play has now done just over 2,100 GPS logged kms and had 3 chassis cuts/mods done.

PS; As a side note, Greg was back on Pink Lake this arvo sailing and said the surface was dead smooth. Shame we have more rain forecast for tomorrow.

Cheers Chook
(lots of edits, as my spelling is NOT good. )

Ok Chook, a couple of questions to clarify your' modifications.

1. you have settled on a mast position, forward/aft, does this differ from the LLM'S specs?

2. With the bigger sails you are using very little mast rake, is there a relationship between the steep rake angle and moving the seat base forward?

3. Is reducing the camber a result of altering the mast set up and shifting the weight forward or is it related to pilot weight, (I'm wondering if the generous pilot weight places excessive side load on the single row bearings under straight running and if this would result in slower running between tacks)

Great post, I also have a generous amount of static ballast, so just deciding if this info should influence my LLM build. Do you have any comparative performance figures over a stock LLM with you piloting?


Mick.

Errrr you did mean a 5.6m rope loop to measure the yacht to be compliment with the 'International 5.6m Mini class'?

" With the bigger sails on my older standard LLM's, the centre of effort was WELL back and outside the envelope for positive steering. I have to slip well forward under the seat belt, to retain any sort of control. When the speed/power increased the back end would keep letting go and steering was really sketchy."

Nice pictures and information. Thanks for posting. My mini has the same issues as above. Mast is in about the exact same place as yours but is raked at 11 degrees. I have an adjustable mast step as well but it's as far forward as possible and I like the rake as it is so the boom is as close to the deck as possible. I did some experimentation at the last regatta on the last day of racing. I flipped the axle upside down which raised the rear of the boat about 2.5''. It completely changed the steering by taking rake out of the mast and changing the ce location. Now instead of sketchy steering and rear end breaking loose It hiked a lot. Since then I've flipped the axle over into the original position and bought a smaller diameter front tire so the boat overall sits lower. It lowered the front about 1.625''. Hopefully that will be a nice compromise between the two. I just need to get a chance to do some testing.

Just like tires, less surface area means less drag! Less drag means more speed!

TP1, running the single row standard ball bearings with camber is a compromise, they are designed to be loaded at 90deg to the axis, paired or not used as wheel bearings they are subjected to axial loading equal to the sum of horizontal vectors of wind load and centrifugal loads when turning plus gravity when the axle has camber. Without camber the reduction in axial loading is reduced by the horizontal vector due to gravity. This is an additional loading exacerbated by increased weight of the operator but would require a lot of mathematics to determine just how much this affects resistance within the bearing. However the vector for a 120 Kg operator would be double that for a 60 kg operator.

Anyhoo ......... these axial loads will cause rolling resistance within the bearing . There are a couple of alternatives such as angular contact ball bearings, a lot more expensive or taper roller bearings with an inherent greater rolling resistance than a single row ball bearing and requiring preload and lubrication issues ie seals required.

I have read that some are removing the inner seals on the 6204 bearings and running light oil rather than grease. I suspect that this gives very marginal advantage at the upper end of performance but may in fact provide a greater advantage from a standing start. Of course any advantage could easily be negated by incorrect tyre pressure or wheel alignment.

I guess the only way to determine how much the axial loads affect performance would be to calculate the sum of horizontal vectors for a given situation, apply that as an axial load to a bearing and measure the torque difference required to rotate the bearing compared to the same load applied radially.


Fortunately I don't plan on any serious competition sailing so absolute performance is not a critical issue for me.

Mick

So there it is Chook,

Radial roller bearing physics in a nut shell. Whether it's one degree or 90 degrees, it's not vertical.

Team wally covered it pretty well too.

I hope this leaves you without a doubt.

A whole lot of really technical stuff about bearings and howntheybaremused.

medias.ina.com/medias/en!hp.tg.cat/tg_hr*ST4_1652155275

An interesting read with lots of pictures.

No not at all Kaonaona. I like the different ways people think. All positive for the sport, I feel.

I do know for sure that there is a HUGE difference from the cheap bearings to the quality of the more expensive ones.
The last lot of cheaper bearings I was supplied with, didn't even have a recess on the inner race for the rubber seal to run in and the rubber seal didn't have any tin support in its inside side wall each side of the bearing either. Very nasty construction, but at a cheap price.
Old saying I guess, you get what you pay for.

TP1,

Green thumb??? I might be too old for that lingo because I don't know what that means!

Lame ha.

Just a little comment on the bearing spacers.

Unless the wheel hub is steel and the bearings are pressed in with a very tight (non-slip) fit, or else the hubs are fitted with end caps to lock the bearing in place, then the use of spacers to attempt to equally share side loads by both bearings is useless. If attempted, the spacer in that case needs to be only between the inner races and then machined exactly as per the width between the outer races. That is very hard to achieve with precision bearings. Most motor shafts have only one bearing "fixed or captive" with a stepped shaft to the second bearing. This allows the second bearing to "float" without preload which will destroy the bearing. So in actual fact only one bearing is ever taking the side thrust.

In the case of plastic hubs it is impossible to fit a bearing tightly to plastic so that it cannot move. So it is necessary to rely on only one or the other of the plastic inner hub shoulders to accept the side thrust. Therefore only one bearing is accepting side thrust at any time. Again, a spacer would not be of any use.

Sorry "teepeewun" (good name for your yacht) but I don't agree about sharing side loading in one wheel. Firstly forget about the plastic adapter, they look neat but only make up the gap between bearing and hub to allow an incorrect and poorly seated bearing. They add to the problem by allowing the bearing outer to be less supported by the plastic wheel hub and I'm not impressed there. A steel adapter would be far superior.

I agree having a sleeve tightened between bearing inners does keep the alignment of the bearings true within the plastic hub - and that is worthwhile. But the side weight transferred from one bearing via the sleeve to the other is in turn transferred via the balls (pardon the expression) to the outer shell. That outer shell is still free to move out of the hub or the adapter and therefore cannot accept a side load.

In my opinion the Fallshaw plastic wheels are accurate mouldings and run true, machined spacer between inners races is good, but bearings and shaft sizes need to be selected to eliminate those plastic adaptors.

The fact is that the bearings are clamped together via the sleeve and axle. This changes the side loading to a more vertical force, down on the outer bearing and up on the inner bearing.
6204's are ideal bearing size and instead of changing bearing sizes for different wheels it is cheaper/easier to adapt the wheel to suit. This allows interchanging bearings where needed eithr between yachts/wheels or even sailors. besides the more who use the same size the cheaper easir itt is to buy in bulk.