I can’t believe how nice this turned out! I received some composites advice from some of you out there and I don’t think I was paying enough attention when I read the emails. I thought you were recommending 3 x 20 oz layers of glass + a layer of Kevlar on the outside of the 1/2″ foam core skin. After laying down my Kevlar first, then a single layer of 18 oz Woven Roving, I realized that this was super thick and stiff and heavy. So, I went back to the emails and realized that the suggestions were somewhere around a TOTAL of a 20 oz. outer layer. duh!

The advantage to using this really thick E Glass Roving is that it covered over all of the seems between my 1″ Styrofoam straps very nicely! It also covered over all of the small holes and dents, etc. After it cured, I have a very smooth, very tough and strong outer skin.

The disadvantage to a single layer of this Roving, is that all of my weaves run in line with and at 90% to the deck. I am considering adding a second layer of this 18 oz Roving at 45 degrees to the first, but that is going to make for one VERY thick, heavy and strong outer skin. Not sure what to do on the inside of the 1/2″ core…

Ben is pin-pricking the Styrofoam plug with a nail board.

Ben and Matt came over and helped. We started by filling in all of the small holes and dents in the Styrofoam plug with a thick mixture of epxoy/micro balloons. Then we pin pricked the entire plug and squeegeed a 1-1 (volume) mix of epoxy and micro over the whole plug filling in all of the pin pricks and seems between the foam strips. Then we laid down our first composite layer – a golden layer of Kevlar.

Then we put down the 18 oz woven roving e glass fabric and wetted that out. Since it is so thick, it took a TON of epoxy! I draped a peelply sheet over it all to leave a rough texture so that if we decide to add another composite layer, the epoxy will adhere properly to the cured layer.

Next, I will either add another outside layer (or not, depending on the advice I get). I’ll pull it off the kayak hull, flip it over and take out the styrofoam ribs, leaving only the 1/2″ Styrofoam core. Then I will remove areas of the 1/2″ foam core and fill with epoxy or wood for hard points where I will be putting fasteners through, etc. Next, I’ll add a layer of Kevlar to the foam with another layer or two of e-glass roving. This time, the layers will wrap around the deck edges and overlap a few inches to the outside. I would like to vacuum bag this one, as the foam sections will be out and we can put the entire boat in a large plastic bag.

The next step will be to make the bulkheads, hull floor reinforcements, and drive leg bay (and the seat rails and seat). I was thinking of making the bulk heads in two halves – the bottom half which could be bonded and glassed right to Within’s hull, and the top half which could be bonded to and glassed right to the Deck top. When the two halves (the deck and the hull) get bonded and glassed together, it would be easier to glass together a straight seem between the midway point on the bulkheads that to try to glass in the upper perimeter.

Thanks for your comments on my previous Within Human Powered Boat logo ideas. Most of you thought that perhaps the logo wasn’t strong enough and I agree. I was sort of going with a typical boat logo – you know, sort of scripty and often free-hand or brush stroke. Human powered boats are interesting, different and represent a new approach to water travel. The logo should say that, so I gave it another shot.

Let me know what you think, as your comments really do help the whole process.

Click to enlarge

I like the above two logos the best. They are modern looking, clean, will reproduce well and will be fairly readable and visible on Within’s hull. The Within logo on the upper left represents a prop spinning – perhaps the i dots resemble bubbles that a spinning prop might produce. The dots the form a circle in the middle of the logo type focus your attention to the middle of the logo – or WITHIN the logo. The circular shape created by the dots also resembles a gear. The shape formed by the top of this logo resembles the shape of the boat travelling left with the flying dots forming the shape of the canopy.

The logo on the upper right is an exagerated version of prop spin. It looks more like a spinning prop, and the double concentric circles looks like two chain rings. You definitely think of circular movement – like the turning of pedals, the spinning of a prop.

These four logos self explanatory – the man forming his arms directing attention to within himself. Or, he is holding a gear above his head. I think this one is too complex

I’m on a roll now – somebody stop me.

I’m on a roll now – somebody stop me.

Styrofoaming Within’s deck is very tedious work – like assembling a giant three dimensional puzzle, and I’ve found that I need to take short breaks or I start to get sloppy. Unfortunately for you, the breaks are resulting in these daily treatises showing up in your inbox. This is good though, as it really gives me a chance to solidify my ‘greater good’ message that is the basis for the human powered trans Atlantic expedition.

Yesterday, I talked about why Human Power was important to me – today, my topic is why Human power should be important to EVERYONE.

Our fragile environment

United States burns 20.4 million barrels of oil per day. We are damaging our environment beyond repair by burning copious amounts of hydrocarbons into our atmosphere. According to Al Gore’s “Inconvenient Truth”, global warming is melting the ice shelf and global sea levels could rise by over 20 feet. Looking at the global temperature data and it’s correlation to greenhouse gas emissions, I believe there is indisputable evidence that burning hydrocarbons is responsible for most of the global warming that is wreaking havoc on our weather systems.

Aside from the frightening global warming issue, I am also deeply concerned about our attitude with regard to consumption. Up until just last year, the US was the worlds largest consumer of natural resources. According to David Suzuki’s “Sacred Balance” (I absolutely LOVED this book – everyone should read it), since 1940, Americans alone have used up as large a share of the Earth’s mineral resources as all previous generations put together.

The real scary thing is, as of last year, consumption in China eclipsed that of the United States in all the worlds resources but oil, and China’s 1.3 billion person economy is growing at a frightening 8% annually

Why is this concerning? There are around 6 billion people living on this rock today. Estimating future population growth at only 1% per year, the numbers are staggering. By 2015, experts estimate there will be 7 billion people on the planet. By 2050, there may be as many as 10 billion people living on Earth. Can mother Earth support this extended family? When will we reach the limit of our resources?

We live in a culture where incentives exist to encourage doing more with more – not doing more with less. Doing more with less is called “efficiency”, doing more with more is called “Gluttony”. Bigger, faster, more powerful vehicles that consume more fuel at faster rates, larger meals wrapped in complex, land-fill bound packaging, disposable products filling store shelves – you get the picture. Take the new wave of hybrid cars for example. Hybrid technology that was intended to produce spectacular fuel economy, was flipped around by car makers to instead, produce more horsepower for their new hybrid SUV’s! Less green, more mean.

Human Powered vehicles are all about trying to do more with less. How to go faster or farther with less energy. Technologies Incorporated into human powered vehicles like aerodynamics, wheel rolling resistance, mechanical efficiencies and size and weight optimization are directly applicable to the cars and boats and other vehicles that we rely upon in these modern times. Most importantly though, Interest in human power represents an essential shift in basic philosophy from one of ‘feasting on earths resources’ to a ‘do more with less’ ideal.

Health

It is true that the world needs to pay more attention to human power as a step in saving the environment, but there is a far more important, pressing and urgent concern at hand here in North America and spreading quickly throughout the rest of the world. We are killing ourselves and human power is our only savior.

3 million years of evolution has produced an animal whose natural environment probably consisted of walking the distance of a full marathon each and every single day*. Now take that animal (also known as a “human being”), and stick him in a small cage, rob him of natural sunlight, make him sit in a chair all day and feed him a steady supply of chemicals and refined foods.

Is it any wonder that 60% of North Americans are over weight? Described by the World Health Organization as an “escalating epidemic”, obesity is “one of the greatest neglected public health problems of our time with an impact on health which may well prove to be as great as smoking.” Being overweight leads to many serious medical problems like high blood pressure, high cholesterol, heart disease, type 2 diabetes, and many other health related issues.

An unnatural sedentary lifestyle causes chemical imbalances in our bodies which can lead to a host of psychological problems. Population studies have shown an inverse relationship between physical activity and depression, and there is evidence that active people who become inactive are more at risk of depression that those who remain active. According to a study from Duke University, aerobic exercise was MORE effective than antidepressant drugs in treating depressive symptoms in three study groups.

The cause of the obesity epidemic and skyrocketing rates of depression is obvious in my opinion. We need to become reacquainted with our “natural environment”. Break out of our cages, get outside and get ACTIVE! Ride your bike, run, walk, swim, climb, row – whatever it takes.

Human power is the power to live. Use it or lose it.

* this refers to a Columbia University study published in early 2005 that suggested “you would have to walk 5.7 hours a day over fields and hills to approximate the energy expenditure of early humans”. I have looked for the actual study, but all I could find was many references to it on the Internet.

Why I like human power and finally, a name for the boat!

The day before the Las Vegas marathon, as I lay in my lawn chair trying to maximize my angle to the low December sun, I got to do some deeper thinking about why “human power” is so important to me. I mean, some people really get into WW11 history, some go nuts over collecting wooden toys and some guys build robots. What is it about human power that turns my crank?

Our passions are obviously related to our personalities. Being a typical male, I am hardwired to dig technology, physical activity is my life-blood, and I like the outdoors and to travel. I also like long walks on the beach and poking dead things with a stick.

As a young kid, I remember reading a National Geographic feature story about a team who rode their ’10 speed’ bikes from Argentina to Alaska. I was riveted by their story. This really spoke to me. The whole idea of riding my bicycle distances longer that we had ever driven our family car was something that resonated deeply with me. I read that National Geographic story about a dozen times.

I saved money from my paper route and purchased a brand new ’10 speed’ bicycle. Wow! It had 10 speeds and drop handle bars just like the ones used in the national geographic bike tour. I rode it everywhere. I duct-taped a transistor radio to my handle bars so I could listen to all the 1970’s hits on CKXL Calgary radio station while I biked the daily 10 mile route from my house in Lakeview (there was no view of any lake) to my downtown paper route.

My passion for riding bikes returned just after I graduated from SAIT – a technical institute where I received a diploma in engineering, and an education in how to party almost every night, and still pass exams. Phil Evans talked me into riding our 10 speed bikes 100 km from Calgary to Banff. I almost died. I remember reaching the lake at LacDesArc and the lights started to go out. I had almost fainted. I think that trip took us a good 10 hours. Now I can ride to Banff, do a 15 km trail run, and ride back to Calgary in less than 10 hours.

We are the products of our past. Looking back, it’s obvious that I would eventually become involved with the design, construction and application of human powered vehicles in some way. We are who we are, and I mean that LITERALLY! – check this out:

I got a really interesting email yesterday from Paul Kolodziej. in case you didn’t know, my last name is Kolodziejzyk – only 3 letters longer than Paul’s. Paul was reading my article in Popular Science magazine and noticed the similarities in our names. He informed me that in Polish, the name “Kolodziejzyk”, and it’s various derivatives mean “WHEEL MAKER”.

Human power to me though, is so much more than travel under our own physical capacity. It’s really about ALL of our power as humans. The power to choose, the power to create, the power to succeed, the power to cross continents, the power to cross oceans, the power to motivate, the power to love, the power to care, the power to inspire, the power to learn and the power to grow. Human power is the power within.

And with that, I have decided upon a name for the human powered trans Atlantic pedal boat.

I hereby christen the boat “Within“. Because Human Power is the power from within. Here are some logo ideas. Let me know if you like one of them (click to enlarge).

My buddy Matt Hoffman, Helen and I flew off to Las Vegas over the weekend for the Las Vegas Marathon. Unfortunately, Helen couldn’t run due to a hamstring tear, but Matt and I had good races. I was aiming for a 3:15 and ended up crossing the line a little over 3 minutes over that goal. Matt was aiming for a 3:20, but hit the wall with 6 miles left to go and finished in 3:29

The run was pretty nice – 16,000 runners with Blue Man Group playing at the start. It was mostly flat with a slight downhill grade and a tail wind for the first half with the inevitable upgrade/headwind for the second half of the 26.2 mile loop which made it a bit challenging. The first hour was pretty uncomfortable, as my right leg from the knee down went completely numb as I knew it would. I have no idea what causes this aside from an accumulation of training hours. It seems that whenever I reach 5 to 6 hours of running per week, my right foot goes numb for about an hour when starting a run. It’s very uncomfortable, but usually goes away after the first hour, so I wasn’t too concerned.

I knew when we first started out that the out-leg would have to be at a slightly faster pace due to the tail wind and favorable slope, so I reached the half way point with a 3 minute buffer on my time. Then I just tried to hang onto that 3 minutes for as long as I could on the home stretch. I thought I was doing a pretty good job though, as I was fluctuating between 1 to 2 minutes over my pace by the final 6 miles. That’s when I started to really feel the soreness creeping into my legs and even though it felt like my pace was the same, my speed really started to slip.

That last 6 miles was very difficult and took quite a bit of focused mental effort just to maintain an aggressive pace. The agony you feel from shooting pains and fatigue in your legs during that last 10 km is hard to explain to anyone who hasn’t experienced it. At every mile marker I would check my pace band, and be shocked to see that I had lost another minute! But that only fueled my determination to mitigate the time slippage and push through the pain.

I was pretty happy to cross the finish line at 3:18:52, only about 4 minutes slower than my goal. As it turned out, I would consider this a personal best marathon even though I ran a 3:16:46 at Tucson in 2004. Tucson was an all-downhill marathon and I finished in the top 20% of my 40 to 44 age group. In Vegas, I placed 22 nd out of 504 runners in my 45 to 49 age group which was a personal record top 4.3% finish.

Here is a chart that I keep showing my AG % finishes for all races since 2001:

I waited at the finish for Matt, who crossed about 10 minutes later. He was with the 3:20 pace group until the last 6 miles, then suffered the same bonk fate that I did and had to let his 3:20 dreams slip away. All in all, it was a fun weekend – caught a show, rested a bit and we both had great races.

Helen was sad that she couldn’t participate, but she needs rest and recovery right now, as we both are committed to two Ironman races this spring and summer Ironman Arizona in April and Ironman Canada in August. Training for Arizona starts very soon.

Greg posing beside a fine art sculpture in the Mandalay Bay lobby.

Until just yesterday, I was calling the part of the boat we are making “the curved top part”. Thankfully, Rick told me that it’s call a “deck”.

Here is a web page with a list of boat parts:

http://www.mum.edu/exss_dept/sailing_club/sail/learn_to_sail/lesson1.html

That goes a long way in demonstrating just how ‘out of my element’ I am with this trans Atlantic human powered crossing. Calgary isn’t exactly the boat capital of Canada and I don’t exactly stem from a long family history of maritime explorers. In fact, I know one guy who owns a boat and it’s my brother in law Pat Lor – a ski boat that he keeps at our cabin in Whitefish, MT. We are welcome to use it whenever we like, but I’m always hesitant because I’m not a big fan of loud gas guzzling motors, and backing the beast and it’s trailer down our steeply sloped driveway.

I do own two smaller boats, a pedal flippers powered Mirage Adventure and a pedal prop powered Shuttlebike which I converted to a human powered recumbent boat. My experience with these small boats, however, is limited to nice, sunny, warm days on an idyllic lake in Montana – not the open ocean.

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Todays progress:

My official expedition training buddy Greg Bradley (right) came over today and lent a hand gluing down pink foam strips to the deck frame. Also in attendance was my other Ironman friend and expedition official video man Matt Hoffman (left).

Ben invented a pretty nifty tool to cut the foam strips with a 90 degree angle on one side, and a 15 degree angle on the other. We place the strips so that a 90 degree matches up to a 15 degree which allows a slight curve and it seems to work pretty well in almost every area of the mold.

Once the strip has been hot glued to the form, I hold them down with small concrete nails until the hot glue dries. This seems to work OK. I’ll have a thousand little holes to fill with an epoxy/micro slurry before we glass it, but it should be smooth enough.

The tight curved areas of the nose and tail are way too small to bend the foam strips around so I think I will just fill them up with expanding foam and carve/sand the shape smooth. This will be far easier and more accurate than trying to mess around with these pink strips. Also, we plan on filling the bow and stern tips with expanding foam for buoyancy anyhow.

The foam strips are fitting together fairly smoothly. I sanding down an area to see how smooth we could get it after sanding, and it was OK – you can still see the joins, but they are difficult to feel with your finger tips. I would hope that the fiberglass fabric would ‘drape’ over these seems and smoothen them over. If not, we’ll have to slather a layer of epoxy/micro over the whole deck after the fiberglass dries, then sand it smooth before paint. But, this isn’t a streamliner, and it probably does not have to be perfectly smooth, so perhaps just leaving small imperfections in the surface will be OK. Maybe paint and primer will fill them in.

Here is the plan:

1. Finish gluing down the pink strips

2. Fill in the nose and tail areas with expanding foam

3. Carve and sand down the expanding foam

4. Sand down the entire surface of the mold to as smooth as possible

5. Fill in the holes with epoxy/micro (smoothen when wet – do NOT sand)

6. Cover deck with 3 (how many??) layers of fiberglass fabric and 1 layer of Kevlar (any advice on how many layers to do??) and wet out with epoxy resin.

7. After the Epoxy cures, sand down the sacrificial finish layer using more epoxy/micro to fill in any holes, divots or visible seems.

8. Pull the deck off the kayak hull and carve out the 1.5″ thick Styrofoam sections

9. Rough sand down the inside foam

10. Lay down (how many layers?) of fiberglass on the inside (any Kevlar required here??) and wet out with epoxy resin.

11. Build the bulk heads and drive leg well and glass into the hull.

12. Build the seat and rails and glass down to the hull

13. Glass/bond the deck onto the kayak hull.

14. Cut the canopy top off

15. Glass in the top part of the bulk heads. I’m not sure how to get into the bow and stern compartments to glass in the other side of the tops of each bulk head wall? Perhaps I wait until we add hatches, then crawl into each space for some extreme fiberglassing.

16. Heat form the Lexan canopy window.

17. Capsize and stability testing

18. Prime, sand and paint

Matt (left) and Greg B (right)

The video clip above is a short 5 minute segment I put together using the footage we shot from the last couple of days. I wanted to preview how the light was in the shop and other areas of the house as well as how the Sony HDR-FX1 HD camera handled various conditions like hand-held steadiness, close-up focus, 1080i high-def image quality, etc.

It worked out kind of neat, so I uploaded it to YouTube.com for you to check out.

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Todays progress:

I finished the Styrofoam skeleton today – it went pretty fast actually. The sections are hot glued onto the main profile. Next I will lay over narrow, 2″ wide, 1/2″ thick Styrofoam strips, then sand it smooth.

http://www.adventuresofgreg.com

We made some decent progress on the test boat yesterday. Ben “BEAN” Eadie came over and built a hot wire cutter for the foam sections, and my Friend Matt “CLAMP” Hoffman contributed his expert filming talents.

I have not mentioned this yet, but I invested in a High Def video camera with the objective of filming this entire project which might find it’s way into a documentary, TV series or film some day.

Matt “clamp” Hoffman is on board as our official expedition videographer.

We’re all professionals here – so don’t try this at home. Clamps history in the film industry is long and accomplished going back as far as a couple of days ago when he browsed through the Sony HDR-FX1 manual and learned where the record button was. And of course, you know some of my extensive maritime background which consists of driving over bridges crossing the mighty Bow river here in Calgary – at least twice per day – sometimes more!

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Assembling the styrofoam sections:

I sliced up my computer model into 29 sections then printed each sections outline onto tiled letter-sized sheets of paper which I taped together.

For the main profile I had to tile together 88 sheets of paper and then cut around the perimeter.

The main profile section was traced onto multiple sheets of 2″ thick pink Styrofoam, cut out and assembled into the Hyak kayak hull. After the main profile was secured into the middle of the kayak, I sanded down the edge with a wire brush to get the line smooth. The 29 perpendicular sections will be cut out of 1″ thick Styrofoam and hot glued to both the main profile and the sides of the kayak.

To facilitate the Styrofoam cutting, Ben whipped up this nifty hot wire cutter which works pretty slick.

This week, I’ll be in the shop alone and I will start gluing the sections into place. Hopefully, we can start fiberglass on the weekend or early next week.

I’ve been working with my 3D design software Strata 3d, trying to nail down a final design so that we can get started building it! Above is a short video of the design as it is now. After measuring the Hayak kayak hull, Ben made a very accurate model of the original kayak hull in SolidWorks. He sent me the 3D file for the hull and I created the rounded top section in Strata by skinning a row of bezier curves.

(click photos to enlarge)

The next step is to virtually (in software) carve the top section into vertical slices 18″ apart. Then I will print these patterns out and use them to cut out 1″ thick styrofoam sections. These foam sections will be bonded into the Hyak kayak hull and then 1″ strips will be laid across and glued to the sections from bow to stern. After sanding the styrofoam, we cover with fiberglass and repeat for the inside leaving the 1″ thick foam strips to act as sandwich core material.

The drive leg is shown is some detail below. I’m going with a mix of bike chain and the right angle gear box. The SRM cranks turn a chain that passes through two 1/2″ stainless steel tubes down to the gearbox. The tubes will also be reinforced with cross braces and covered with stainless sheet. This will double as the structural member supporting the prop and gear box below.

Since this ‘fin’ is only a 1/2″ thick, it only needs a 1/2″ wide slot in the kayak hull to fit through. The slot has 5″ tall walls to prevent water from flooding the boat. To remove the drive leg, the narrow slot leads to a larger square well in front of it that the gear box and prop will fit through. The drive leg will be fastened down to the seat rails and a through bolt in the well. A square plug will fit into the larger square opening in the well to seal it off from water and to smoothen out the bottom of the boat hull. I could further seal the narrow part of the drive leg well with two smaller, thin plugs that fit into both sides of the gear leg.

I have not yet marked off where the retracting canopy top will be cut-out, but I would need to make sure that once it is retracted, I can lift the drive leg straight up and out.

The seat is mounted to two 1″ square tubes running length-wise down the hull floor and can be adjusted forward or back. I still need to figure out a way to move the seat out of the way to access the rear compartment.

Only half of the bulk head in front of the drive leg is shown – it will completely seal off the front compartment. I have NOT shown the rear bulk head which will completely close off the rear compartment.

We will probably start building the foam plug on Monday. I’ll keep you informed.

The Hyak donor kayak from Nimbus Kayaks arrived last week!

It is in pretty decent shape, but does not include a top or any bulkheads – just the bottom hull. That’s OK because I would have just cut out the top anyhow before adding my own top. Ben came over yesterday and build a little Styrofoam stand for the kayak, then proceeded to take measurements so he can model the kayak hull in SolidWorks. We’ll use the Solid Works model to build the canopy top, and then use that 3D model to generate sections which we will cut out of foam.

Check out Rick Wianecki’s Frank-n-liner streamliner at Warrens recumbents.com site:

This is exactly the male mold construction method that I plan to use for the test boat. I am a little concerned about wetting out fiberglass and not using a vacuum bag, as the vacuum would surely deform the thin foam strips, but Rick maintains that he never had any problems with the wetted glass bubbling or peeling up. I’m thinking we could use stretchy film wrap to press down the wetted fabric without distorting the mold.

TB-1 test boat (“TB” for ‘Test Boat” – not a very inspiring name is it….)

Testing the mechanical efficiency of 3 types of drives

There has been some discussion at HPV boats forum regarding the efficiency, pros and cons of various mechanical drive approaches. The task with regard to human powered boats is to transmit the direction of power input from cranks which rotate in a plane that aligns with the boats length, to a prop which rotates in a plane perpendicular to the boat and the cranks. Rick Willoughby typically uses two right angle gear boxes and a shaft to transmit power from the cranks to the prop. Others such as Warren Beauchamp use a chain that twists 90 degrees from the chain ring on the cranks down to the prop.

The advantages to using two gear boxes and a shaft are mostly that it is structurally very solid and strong – probably a good combination for an ocean crossing. The disadvantage to this approach is potentially less mechanical efficiency than a twisted chain due to the heavy gear box.

The advantages to using a twisted chain is light-weight, possibly good mechanical efficiency and easy to replace standard bicycle parts if something goes wrong. The disadvantages to using a twisted chain is related to the fact that the chain isn’t really designed to twist, and it may be difficult to replace a broken chain in the middle of the ocean. I’m just not certain how long a twisted chain drive will last.

So, at least with regard to the mechanical efficiency questions, I thought I would spend some time and conduct a few experiments designed to elicit exactly what the power ‘cost’ is for each approach.

To summarize, here is the mechanical power efficiency % for each drive configuration for average resistance of a prop spinning in water at 80 rpm at the cranks (relative to a straight chain at 100%):

STRAIGHT CHAIN = 100%

RIGHT ANGLE GEAR BOX = 94.1%

TWISTED CHAIN = 93.3%

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THE STRAIGHT CHAIN

As a baseline – or control, I set up a drive that was a straight chain running from my 39 tooth SRM watts meter chain ring to an 11 tooth cog mounted on a bicycle bottom bracket. On the other side of the bottom bracket, I mounted a standard bike chain ring. A chain runs from the large 53 tooth gear to a 12 tooth gear on the rear wheel of a road bike on a magnetic resistance trainer stand.

The lower chain ring and bike wheel simulate similar resistance of a prop spinning in water. In this case, I am looking for an average resistance of around 150 watts of power to turn the cranks 80 rpm. The photo above shows a magnetic resistance roller and a wind resistance roller (red) on the rear wheel, but I found that neither was required to maintain about 150 watts of power to turn the cranks at 80 rpm. For this experiment, the rear bike wheel was freely spinning – this had the added benefit of being more consistent between drive leg configurations, as the magnetic and wind rollers change resistance slightly due to various pressures against the tire and temperature.

The control using the straight chain would be a best case scenario, as there is very little mechanical loss from a straight chain. Obviously, it is an unacceptable drive option because the direction of power transmission is in the same plane. (I would have to be sitting SIDEWAYS on the boat in order to use this).

Here are the results:

FREE SPINNING = 0 WATTS
No chains at all, just the main crank and pedals spinning freely. The SRM power meter was calibrated to measure 0 watts from this free spinning condition.

NO RESISTANCE = 2 WATTS
The bottom chain was NOT connected to the bike wheel. This test measures the no-resistance mechanical loss of the SRM 39 tooth chain ring with a straight chain to the 11 tooth gear mounted on the lower bottom bracket turning a pedal and chain ring with no chain or resistance.

RESISTANCE AT 80 rpm = 135 WATTS
This configuration is as shown in the photo above. The bike wheel is linked to the drive and simulates typical resistance of a prop spinning in water. It required 135 watts of power to turn the SRM cranks at 80 rpm.

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THE TWISTED CHAIN

The chain twists 90 degrees from the 39 tooth SRM chain ring down to the 11 tooth gear mounted on a bottom bracket. The return side of the chain is tensioned and positioned with a chain guide (orange roller). A free spinning bike wheel with a 12 tooth gear provides the same resistance as the control. Note that gearing and therefore, the resulting resistance for both this configuration and the control is exactly the same.

Here are the results:

FREE SPINNING = 0 WATTS
No chains at all, just the main crank and pedals spinning freely. The SRM power meter was calibrated to measure 0 watts from this free spinning (same as the control)

NO RESISTANCE = 8 WATTS
The bottom chain was NOT connected to the bike wheel. This test measures the no-resistance mechanical loss of the SRM 39 tooth chain ring with a twisted chain to the 11 tooth gear mounted on the lower bottom bracket turning a pedal and chain ring with no chain or resistance.

RESISTANCE AT 80 rpm = 144 WATTS
This configuration is as shown in the photo above. The bike wheel is linked to the drive and simulates typical resistance of a prop spinning in water. It required 144 watts of power to turn the SRM cranks at 80 rpm. The twisted chain required 9 more watts of power than the straight chain to turn the cranks 80 rpm.

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THE RIGHT ANGLE GEARBOX

The chain runs straight from the 39 tooth SRM chain ring to an 11 tooth gear mounted on one axle of a Mitrpak right angle gear box. A 53 tooth large chain ring is mounted on the other gear box axle which turns a chain connected to the 12 tooth bike wheel. Note that gearing and therefore, the resulting resistance for both this configuration and the control and the twisted chain is exactly the same.

Here are the results:

FREE SPINNING = 0 WATTS
No chains at all, just the main crank and pedals spinning freely. The SRM power meter was calibrated to measure 0 watts from this free spinning (same as the control)

NO RESISTANCE = 8 WATTS
The bottom chain was NOT connected to the bike wheel. This test measures the no-resistance mechanical loss of the SRM 39 tooth chain ring with a straight chain to the 11 tooth gear mounted on the right angle gear box turning a pedal and chain ring with no chain or resistance.

RESISTANCE AT 80 rpm = 143 WATTS
This configuration is as shown in the photo above. The bike wheel is linked to the drive and simulates typical resistance of a prop spinning in water. It required 143 watts of power to turn the SRM cranks at 80 rpm. The right angle gear box required 8 more watts of power than the straight chain to turn the cranks 80 rpm. The gear box required 1 less watt than the twisted chain, but 1 watt is easily within the margin of error, so I would consider both drives equally efficient.

The nitty gritty details

To start with, I used an old exercise bike with a roller pressing down against the rubber wheel. This didn’t work at all because the bearings in the wheel are old and changed resistance periodically.

The SRM power meter computer showing crank rpm and power in watts.

This is a third drive option that I tested, but it didn’t work at all. It’s a flexible drive shaft from my Shuttlebike kit. There was far too much resistance and the shaft just twisted up inside the housing.

I had to fabricate a connection for the flexible drive shaft.

The flexible drive shaft connection to the SRM cranks and the lower bottom bracket

The Mitrpak right angle gearbox.

To make a collar to fit onto the gearbox shaft, I cut an axle from an old Shimano Octalink bottom bracket in half and inserted a smaller diameter stainless steel tube into it and welded it in place. This allowed me to use the standard spider bolt to mount the chain ring. The smaller diameter tube was a press fit onto the right angle gear box shaft. To hold the collar in place, I drilled and tapped a hole for a set screw.

The small 11 tooth cog fit onto the gearbox axle the same way – I welded a short tube to the back plate of the cog and press fit that onto the gearbox axle. It is held in place with a set screw.