The "Aerowherry" a lightweight rowing boat (was going to be a canoe........)

[Randonneur]

I was thinking of you today when I read today's Duckworks main item.
http://www.duckworksmagazine.com/11/designs/alice/index.htm

Just a tad lighter at 10 lbs!

Pete

[Jeremy]

Phew!  That's impressive, but a tad expensive for a 12ft kayak.  I just quickly costed the 190ft of 0.24" carbon fibre tube needed and it comes to around £350, to which has to be added the cost of the plywood for the frames, fabric, paint etc.  For comparison, buying all the alloy tubes for the Aerowherry hull (inc frames) would cost about £75.  

I managed to weigh my frame last night and it is currently 8.2kg without the fabric, floorboards, seat etc, so I'm going to guess that my 16ft boat will end up at around 11 to 12kg, a bit more than double the weight of that kayak, but more than double the internal volume.  Weighing was fun, as I pondered how to do it for a while before I hit on the idea of turning it on end and standing the whole boat upright on a set of digital scales.

Interestingly, the designer/builder of that lightweight kayak has used the same covering that I've chosen, heavy weight Ceconite 101, it's nice to know that he's found it tough enough to use on a boat that gets folded up and backpacked.  I like his idea of coating it with hypalon, too, but it seems mighty expensive.  The cheapest I can find is around £60 a tin, which seems a lot for paint.  I think I'll stick with conventional paint to save some money, or maybe try one of the acrylic, water based, flexible coatings, like this stuff: http://www.plastidip.co.uk/eStore/index.cfm?type=Domestic_Solutions/HCF&stage=1 (has anyone tried it, by any chance?).

If anyone has any ideas for reasonably priced, flexible, paint I'd welcome them.

Jeremy

[BrianP]

Alice also uses expensive arrow shafts for her connecting pieces which adds more cost.

When you think of how much all the epoxy, varnish and paints costs, (in the hundreds), for a plywood build, the hypalon paint at £60 is good value I think. It's pretty tough.

Brian

[BrianP]

This hypalon paint is £29.99 per 500ml?

http://www.campandfish.co.uk/flexithane-hypalon-paint-black-534280-20061-p.asp

This hypalon is £31.99 per 500 ml.

http://www.mailspeedmarine.com/inflatable-dinghy-repair-care/ibs/inflatable-boat-paint-hypalon18198-1820363.bhtml

Looks like so far only finding £60 per litre?

Brian

[Jeremy]

Thanks for digging around, Brian, you've found what look to be the same sort of prices as I've found so far.  I reckon I need at least a litre of the stuff, maybe more.  I've emailed the Performix people to see what they say about using the HCF with their F-799 shiny clear coat, as I think it'll probably look nicer with a shiny finish, rather than a matt  or eggshell one.  The price will end up being at least that of hypalon, but will look nicer, I'm sure.

I've painted fabric covered aircraft with ordinary 2K PU paint, with just the plasticiser added that they use for painting flexible plastic car parts and found that it works OK and gives a very nice finish, but it needs spraying and I don't have access to the specialist facilities needed to spray this stuff any more.

I'm almost tempted to try ordinary marine 2 pack paint.  I painted the topsides of my old yacht with the International stuff, using a foam roller, and was mighty impressed with both the finish and the durability.  I doubt the fabric will flex very much, so maybe that's an option, too (although not a cheap one).

Jeremy

[LASER41420]

Its cheap enough at boat jumbles

Steve

--- On Fri, 25/3/11, Jeremy [via UK HBBR Forum] <[hidden email]> wrote:

From: Jeremy [via UK HBBR Forum] <[hidden email]>
Subject: Re: The Aerowherry build
To: "LASER41420" <[hidden email]>
Date: Friday, 25 March, 2011, 16:12

Thanks for digging around, Brian, you've found what look to be the same sort of prices as I've found so far.  I reckon I need at least a litre of the stuff, maybe more.  I've emailed the Performix people to see what they say about using the HCF with their F-799 shiny clear coat, as I think it'll probably look nicer with a shiny finish, rather than a matt  or eggshell one.  The price will end up being at least that of hypalon, but will look nicer, I'm sure.

I've painted fabric covered aircraft with ordinary 2K PU paint, with just the plasticiser added that they use for painting flexible plastic car parts and found that it works OK and gives a very nice finish, but it needs spraying and I don't have access to the specialist facilities needed to spray this stuff any more.

I'm almost tempted to try ordinary marine 2 pack paint.  I painted the topsides of my old yacht with the International stuff, using a foam roller, and was mighty impressed with both the finish and the durability.  I doubt the fabric will flex very much, so maybe that's an option, too (although not a cheap one).

Jeremy

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[Jeremy]

I've been away on holiday, so no progress for a while.  Today I got back on the build and started making some carbon fibre outriggers to support the rowing arrangement.  These are similar to the laminated wood ones pictured in Brian's post earlier in this thread, although are probably 1/3rd the weight!

The rowing arrangement will be a bit different, because the one thing I really dislike about rowing is facing backwards and not being able to see where you're going.  This is made worse for me because I have a fair bit of damage to my neck, which makes turning my head pretty painful.  Back in around 1874 a chap invented a linkage for reversing the direction of oars, making it possible to face forwards when rowing, in a far more civilised manner.  Many people have since copied or re-invented his idea and several commercial units use the same basic principle, but they all seem to be rather expensive.

I've adapted the original idea from 1874 and used some stainless steel, Teflon lined, rose joints (bought from ebay for a pittance) to make the linkages (rose joints are great, as they are self-aligning, meaning tolerances can be a bit greater).  The oar handles and looms pivot on oilite bushes fitted over stainless steel pins (for low friction and tolerance to getting wet) and I've added some gearing, so that I can use shorter oars and still get a fair degree of sweep with the limited beam I have (I didn't want the outriggers to project far from the hull, as they would make coming alongside awkward).

The carbon fibre outriggers fit to a pair of 1" diameter alloy tubes that support the floor boards.  This allows their position to be adjusted.  The thwart also fits to the same alloy tubes and is similarly adjustable, as will be a foot rest.  This should mean that I can adjust the thwart to get the boat balanced correctly and then adjust the outrigger and foot rest positions to match.  It might also allow me to explore the use of a sliding seat or rigger configuration in the future, as it would be fairly easy to make wheels run on these tubular rails.

The oars will be a combination of alloy tubes for the handle and loom (heavier gauge inboard for better balance) with carbon fibre blades.  I think I've found a way to mould Macon type blades fairly easily - this will be a job for later in the week when I can't get on with covering the frame because of the weather (the hull is out in the car port as it's too big for the workshop).

If the weather holds up long enough I should be able to take some photos tomorrow.  I was too busy today with the build to stop and photograph the bits - after a couple of weeks of no activity it was great to be back building again.

Jeremy

[BrianP]

It's terrific following your build, wondering just what will develop next! Here's a front rower with a solar appendage, perhaps you could add solar panels to charge the batteries for the challenge.


http://frontrower.com/blog/

Looking forward to the pictures.

Brian
 

[Jeremy]

Although I like the automatic feathering and use of foot power with the "Front Rower" I can't help but think that it looks a bit Heath Robinson, with all those bits of string, struts etc.  My interest in forward-facing rowing came from reading a certain rowing blog, specifically this entry: http://rowingforpleasure.blogspot.com/2010/04/this-extraordinary-mechanism-is-fine.html.

The old patent drawing from 1875 was interesting, but I noticed (by searching the espacenet patents site) that there are literally dozens of re-inventions of forward facing rowing devices (quite why the patent office allows previously patented ideas to be re-patented by different individuals years later I don't know).  The one that caught my eye as being a close replica of the Victorian original was this one: http://gb.espacenet.com/search97cgi/s97_cgi.exe?action=View&VdkVgwKey=GB2234217A&DocOffset=42&DocsFound=68&QueryZip=%28rowing%29+%3CIN%3E+ti&Collection=dips&SearchUrl=http%3A%2F%2Fgb%2Eespacenet%2Ecom%2Fsearch97cgi%2Fs97%5Fcgi%2Eexe%3Faction%3DFilterSearch%26QueryZip%3D%2528rowing%2529%2B%253CIN%253E%2Bti%26Filter%3Dgb%252Fen%252Fespacefilt%252Ehts%26ResultTemplate%3Dgb%252Fen%252Fresults%252Ehts%26Collection%3Ddips%26ResultStart%3D41%26ResultCount%3D10&ViewTemplate=gb/en/textdraw.hts&ViewErrorTemplate=gb/en/incerror.hts&DocsFound1=68&BeginHighlight=%3Cspan%3E&EndHighlight=%3C/span%3E&HLNavigate=

I have used the same basic principle, with a 20% acceleration factor (meaning that the oars can be 20% shorter for any given speed through the water).  I've simplified the design somewhat and produced something that looks more like the old Victorian design, but without the need for curved levers.

BTW, does anyone know what the most comfortable diameter of oar handle happens to be?  The tubes I'm using are 1 1/2" diameter, which I think might be OK as it is, but I'm guessing that only long-term use will confirm this.  I can fairly easily make separate handle from something like a bit of Delrin bar, should a different diameter be needed.

Jeremy

[BrianP]

I have 3 pairs of carbon sculls in the garage and all have 1 1/2" handles. Just a thin rubber covering on the grip area. Also happy for you to take a mould of the blades if you wished, although you probably have something special planned for those as well.

Brian

[Jeremy]

Many thanks, Brian, that's a handy coincidence that they match the tube I already have.  I may just get some rubber grip stuff that's used on cricket bats to make the handles a bit more comfortable and stop the alloy giving me black hands in use.

I've started making a blade mould already, thanks.  Nothing too fancy, just a symmetrical shape so that I can use one mould to make both blades.

Jeremy

[Chris Partridge]

Jeremy - you can get rubber oar handles from several rowing suppliers. The latest fad is to use tape: http://www.rowperfect.co.uk/shop/grip-wrap-tape-for-sculls-pair-51.html. The Dragons Den guys liked these: http://www.oarsome-potential.co.uk/sports-range.
I like good old plain wood. No varnish, sanded to a rough finish, and used a lot.

[Jeremy]

Ta for the tips on oar handles, I'll see what I can get locally that might do the job.

I managed to squeeze the best part of a day working on the boat yesterday, so got the fabric on.

Here's a couple of pics:





With luck I should be able to get the reinforcing tapes glued on to all the stringers, keel etc today, and maybe cover the foredeck, too.  I was planning on leaving the aft deck are open, but am now wondering about whether or not to add some extra support and cover it over.

I haven't weighed it again, but I can still lift it with one hand, so I'm guessing it's somewhere around 12kg.

Jeremy

[Timmo]

Wow!

Nuff said.

Tim.

From: "Jeremy [via UK HBBR Forum]" <[hidden email]>
Subject: Re: The Aerowherry build

[Jeremy]

Glad you like it!  One really nice thing about covering a boat like this is that the shape comes alive in just a couple of hours work.  The down side is that work slows down as you're forced to stand back and just look at it from time to time.............  I've never designed a boat before, and, I have to say, I am inordinately proud of the way it's turned out (so far).

I managed to get all the reinforcing tapes on today, just the foredeck covering to add and then it's ready for paint.  I doubled up some of the taping, with one 4" and one 1 1/2" tape on the keel, one 3" and one 1 1/2" on the lower stringers and just a single 1 1/2" tape on the upper stringers.  The gunwales have 3" and 1 1/2" wide tapes.  I've probably gone overboard with all these tapes, but I had a dozen or so rolls of assorted width tapes handy, so thought I'd may as well beef all the likely rub points up a bit.

The skin is pretty tough, certainly a lot tougher than the much lighter aircraft fabric I'm more familiar with.  I think it'd take a fair old wack to tear it - the boat fell sideways off a trestle this morning, with the end of the trestle pushing the fabric up.  This didn't even mark it, so I think it'll stand up to everyday knocks OK.

I have some samples of different paints coming and intend making some test panels up to see which works best.  I'm hopeful that one of them, a water-based coating, Plastidip HCF, will work OK, as it seems to have a pretty good spec, plus, being water based, it'll be easy to apply and clean up.  Failing that I may have to resort to using Hypalon, all that will add a fair bit of weight, I think.

The propulsion unit for the Cordless Challenge is almost finished, too, so I may even get a chance to do some testing before Beale Park.

Jeremy

[Jeremy]

Another update.

I've been testing paint finishes on some fabric samples and have found, somewhat surprisingly, that the water-based Plastidip HCF is simply astoundingly good.  It is incredibly tough, so tough that no amount of bashing and scraping with screwdrivers etc so much as marks it.  It also seems to be very slippery, which undoubtedly aids it's abrasion resistance - stuff tends to slide over the surface, rather than dig in and cause scratches.  Finally, it both adheres well and remains incredibly flexible - I have repeatedly scrunched up painted fabric samples and there is no sign of cracking.

The only downsides are that it doesn't flow well when brushed - it's like using thick emulsion paint - and it tends to form streaks; it's very difficult to get even coverage, especially on translucent fabric.  I've discovered that it seems to spray reasonably well though, so have now ordered some of the sprayable HCF version for the final paint job.  It may be that the thicker stuff can be applied with a roller, maybe that would give a more even finish.

The dried finish is not glossy, it's a sort of semi-gloss, rather like conventional fabric aircraft dope.   This looks fine on fabric, but it may not look so good on a boat where a showroom finish is desired.  I'll happily trade its toughness and abrasion resistance for looks, though.

The other paints I tried were ordinary chlorinated rubber paint, Plastidip solvent-based paint and Hypalon paint.  All these were similar in terms of finish; looking more matt than the HCF, with the exception of the Hypalon paint, that was semi-gloss.  All suffered from the same problem when subject to abrasion, though; they were all slightly soft and tended to "grab" anything that rubbed against the surface, leading to a tendency to scratch.

Overall, it's the ability of HCF to dry quickly to a very hard surface, even with multiple coats, that makes it seem ideal as a coating for a boat like this.  Being water-based is a bonus, as it makes it much nicer to use.  I'm hoping that spraying it (with a cheap HVLP unit) will alleviate the streaking and poor finish problem, by allowing a more even coat to be applied.

BTW, the boat will now be red, as I can't get HCF in silver.  At least it'll be easy to spot when it gets blown away by the wind.  Despite being under my carport it has been blown off the trestles twice today, the last time despite being tied to the trestles.  I've had to resort to filling it with old bricks to stop it getting blown away................

Jeremy

[Jeremy]

I tried another paint test today, this time using HCF with a foam roller.  The bad news is that this is a hopeless way to apply this stuff.  Quite how you are supposed to apply the "paintable" version of this stuff is a mystery, as try as I might I can't get it to go on smoothly with a good finish.

I'm hoping that the "sprayable" version of this stuff that's on its way will go on more evenly.

Jeremy

[Jeremy]

I've been busy making all the little bits that seem to soak up more time, by far, than the hull itself.  I've opted to make the seat, outriggers and foot rest all independently movable on the floor rails, so that I can both get the trim right and adjust the ergonomic relationship between these three bits.

I have a question, if I may, that perhaps one of the experienced rowers might like to answer.  The seat height is 5" above the floorboards, which seems OK (any higher and it's likely to adversely affect roll stability, I think).  The question concerns the height of the footrest bar.  I sat on the floor and measured my size 8 foot and thought that a bar centred a little more than half way up my foot, when it was at a comfortable angle, seemed about right.  This places the foot rest about 6 1/2" above the floor and now I've made it it looks decidedly high.  I can't sit in the boat on the trestles to try it out, unfortunately.

Has anyone any idea as to how high a bracing bar for your feet should be off the floor, please?


On a slightly different note, the outrigger is almost finished.  I've made it from carbon fibre, with a foam core, using a mould I had for an aircraft semi-elliptic spring composite undercarriage.  I had to do a fair bit of "cutting and shutting, plus I've had a lot of extra hand lay-up and filling to do, but it looks reasonably OK.  I've just given it a first coat of primer, so might get it painted ready for some photos tomorrow.

I've opted to stay with a conventional rowing arrangement for now, as making all the parts for the forward rowing arrangement was taking too much time.  If I find I have time at the end of the build I may get the forward rower bit sorted, but for now I'm going for the safe option, so I have a boat to row down the Thames.  I may even have to resort to buying a pair of 7ft 6in oars..................

Jeremy

[Chris Partridge]

Most rowing boats have a board that you can rest the whole foot on. Pilot gigs have bars across that are fairly low, about 6in above the floor, I think (I could measure it tomorrow if you want). I would mock up the arrangement with a biscuit tin and a clothes horse (or whatever bits for tanks/aircraft/submarines/spaceships you just happen to have in your garage - I just love that throw-away comment about 'a mould I had for an aircraft semi-elliptic spring composite undercarriage').
The only rule is that it should be comfortable for you.
Chris

[Jeremy]

Thanks Chris.  I have some alloy tread plate tucked away somewhere, so could pretty easily add a plate to the bar to make a better footrest.  This might then make it a bit more adaptable and make the height less critical.

Sorry about the throw away comment, the mould really was for a single seat aircraft undercarriage, I'm an inveterate hoarder (much to the annoyance of SWMBO) but I justify it by using old saved stuff like this from time to time.

Jeremy