Waterproof bag for folding bike "Little Nellie"

 

I have a solution. I found a Northern Dive 240L Large Bergen Dry Bag With MOLLE System it comfortably fits my 20 inch wheel Oxlane Decathlon folding bike. It has a dry suit zip, and a tube to control air. It has nice rucksack style straps. It has internal straps to keep the bike (or Military kit!) tight, and external compression straps. It also has lots of well made handles for manoeuvring it on to the dinghy or below.

So these are normally around £500, well it is basically a dry suit for a giant square sponge bob, but I got it on ebay for a lot less. I think I need some secondary padding so the sharper bits do not wear through.

I think I could now take an expensive bike on board like a Bickerton or a folding e-bike. The Oxlane is a "standard 20 inch folder, which means it does not really fold so small. (web site says it fits in a 76 by 44 by 66 cm box when folded). Having "float tested" another bike transfering to a pontoon (it failed the test) I bought this bike (Little Nellie) as it was cheep and I didn't expect it to last. It has a good range of gears with a grip shift and six speed derailleur. The short wheel base makes it hard to cycle up Cornish hills though. We also have a e plus electric bike which is about the same size and that is much better on hills as you dont have to try to stand up to pedal. I often use the bike to solve the problem of leaving the car in one port and going back by bike and train to pick it up.

Watermakers!

Fitted (nearly permanently) tested and then pickled a Katadyne Pur Powersurvivor 40E. After struggling to realize the filter had a missing O ring it works perfectly now  with product water about 200 ppm of dissolved solids. I pickled it with 50% mono propylene glycol.  Then to test the emergency desalinator as I had pickling solution. This is a Karadyn MROD  06 ... and it says it was serviced 10 years ago. Considering you need to re-pickle every year I was taking a chance buying it!. But it makes fine 300 ppm water and works well.  

Where we sailed in the pandemic, Humber to Eyemouth and back!

 So sorry for not making a proper blog entry. Summer 2020 we sailed from Grimsby to Eyemough in Scotland  and back. Harbours included Scarborough, Whitby, Hartlepool, Blythe and Amble. Sarah and our kittens were there Grimsby to Scarborough and again for a week in Whitby. For the rest I was single handed. 

You can see photos on my Google Photos album

Fitting a prismatic telescope to a Davis Mk25 sextant

The whole Davis 25 with the prismatic monocular fitted

The Davis Mark 25 is good value for a back up sextant, and while not as accurate as a metal one it is lighter and cheaper. Its main failing is you need to calibrate index and side error every time you pick it up.

During the Covid 19 epidemic I am on lockdown and can't go to Tui  but I have the Davis 25 at home and I am practising sun sights with a baking tray of water or oil as  an artificial horizon.

It has a little x3 plastic telescope. It us actually  better than it looks and x3 does help. But I don't have great visual acuity and more magnification would help at least on land 

I bought a cheap 8x20 miniature monocular. The objective lens is in a conical tube that unscrews. This allows it to mount in the front scope bracket and tightening it centres the monocular.  The frame that holds the prism and eyepiece fits flush against the rear scop bracket and while the whole is to big it still holds in firmly.

I get a clear sharp view of the sun and its reflection and the field of view is about 5 degrees wide which is plenty. Of course the sun appears bigger and for me easier to judge when superimposed or "kissing".

I paid only £2.69 for this on Ebay, they have gone up to abut £5 now. Just search for 8x20 miniature monocular.

The new prismatic monocular fitted, and the standard "x3" (in practice more like 2x)  telescope underneath for comparison

Showing how the mounting works

A dimensioned photo from another ebay listing

 

More ebay listing photos.  The  optics are coated and  so  the objective appears orange from outside. In practice the magnification is more like x5 thanx8. Don't trust the description!

If you want to get the best from your plastic sextant I recommend the book How To Use Plastic Sextants by David Burch. If you want to know more about the mechanism of sextants, including telescopes I recommend The Nautical Sextant by W J Morris. Both are available in print and electronic format

Cocked hats, triangle and astro navigation

Last summer we had a great trip, coast hopping down to Burnham on Crouch and back again. On the way back we were a bit late, or the storms were a bit early. Anyway we spend some time in the Royal Norfolk and Suffolk Yacht Club waiting for named storms to pass. Russell and I got to talking about cocked hats and uncertainty, which is something I had given popular talks about to sixth form students (You can see me on YouTube ) .

The problem that exercised me was that we had a way to construct the most likely position, the symmedian point, a neat way that we could draw as it is a "triangle centre". But what about an ellipse of equal probability, that is the set of with the same sub of squared distance to the symmedian point.  Were the focal points triangle centres? Did the axes of the ellipse go through other triangle centres?

I looked at the Encyclopedia of Triangle Centres but couldn't make any progress. So I asked its editor Clark Kimberling, who asked Peter Moses. These two are the worlds experts on triangle centres. Peter came back with several triangle centres on the major and minor axes. We did some more work together and the result has just been published in The Journal of Navigation. The Geometry of Elliptical Probability Contours for a Fix using Multiple Lines of Position. 

Recently I was in the US for work and got to go to Frank Reed's course on Lunars. at Mystic Seaport. I highly recommend the course and as well as historical interest shooting lunars is a great way to practice getting accurate sextant readings.

..so why aren't we sailing? I hurt my knee working on Tui earlier in the year and I am waiting for it to have recovered enough...hopefully soon.

Tui's Thorneycroft 154 engine is for sale

Our trusted marine mechanic and Humber Cruising Association member John Foster is fitting a new Beta 50. Meanwhile the Thorneycroft 154 (BMC 2.5) engine is advertised for sale on "Boats and Outboards" here.

Photos of it coming out a few years ago and on a trailer. Also comes with box of spares and paper manuals.

Marine or Ham MF/HF radio?

I posted this on the Facebook forum Offshore SSB Radio and Email
and I thought it might be worth posting here as well

If you need an HF/MF radio for safety because of the area where you cruise, specifically sea areas A2-A4 (out of VHF range), you need it to be DSC equipped, which basically means an (Icom) M801 or M802 at the moment. The reason is that you can call for help to ships outside VHF range and they keep a continuous automatic watch on DSC MF/HF. If you have that need, and hence get the marine radio, you can use the same radio on ham frequencies if you have an amateur license. They are not quite as good as a ham radio as they are more awkward to use for spinning the tuning knob to find some one transmitting, but they will do. There is loads you can do with a ham radio (or a marine radio on ham frequencies). Ham nets, Winlink mail, sailldocs, loads of different ways of position reporting like robust packed APRS and WSPR. You can talk to random hams around the world and they will think its cool to be talking to someone "Maritime Mobile". Of course some of this definitely contributes to safety as well as fun. For those thinking of taking their ham license it is well worth it if only that you understand radio including propagation and fault fixing much better than a typical course for a Long Range Certificate that qualifies you to operate a marine MF/HF radio (even when this qualification is very serious, like in the UK, with a long practical test by the CG, mainly on distress procedures and a written exam). There are also email services (sailmail) and nets for cruisers on marine HF frequencies. I think this is where cruisers are tempted to, often illegally, use a ham radio only not a marine one. It is usually possible to open them to transmit on these bands. A slight word of caution that the performance might not be the same as on ham bands for which the radio was optimised. Also if you had a ham radio on board it would be a wise precaution to open it to marine (and aviation) MF/HF bands just in case. But these days there are very few places where anyone maintains a listening watch on marine MF/HF voice frequencies. You may well be better off shouting for help on a popular ham frequency and asking them to relay it to a MRCC by telephone in that situation.