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brandenjg

Working out my speed?

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Hi everyone

I've got a small boat and recently got an outboard for it. I've been reading up about the speed limits on the broads and i've got the problem that i have no idea what speed my boat will be travelling as theres no speedo. My speed options are basically low-high. I've looked on google maps and found a mile straight on the broads with a speed limit of 6mph. I was wondering if i stay at a constant speed and time how long it takes to cover the mile could i work out my speed? Lets say it takes 15 minutes (and 60 minutes = 1 mile) that i would be travelling at 4 mph?

Any advice would be greatly appreciated :P

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You could but I have found when in the dinghy it is easier to rely on the BA rangers, you can tell how fast you are going by the way they wave back to you.

Alternatively you could buy a cheapo hand held gps from ebay for about 10 quid or even download an app for your phone.

The problem with your measured mile is that at the same speed through the water but with the water moving faster slower or in a different direction you will be doing a different speed over ground and broads speed limits ate measured over ground.

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If you're leaving an appreciable wake (enough to rock boats moored alongside the river) then you're most probably going too fast!

Come alongside a private boat and ask for his speed but if it's gps speed you then need to add/subtract the tidal flow (river speed over the ground).

I've never heard of a dinghy being stopped by the Rangers but quite a few should be! :naughty::naughty::naughty:

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If you have a smart phone on Apple or Androids Operating system then there are a wealth of GPS speedo Apps available, the one I downloaded for free even has facility's for anchor watch, heading and the speed can be set in knots, MPH or KPH, if for some reason you want to use it in the car it even facilitates head up display by displaying big bright numbers in a mirrored format so that it reflects onto the windscreen in a form you can read.

My phone was reading from 8 satellites last night which should be enough to give a very accurate reading of speed but unless you have a power supply in your boat for your phone you will only be able to use it for short periods, probably a lot more useful than your measured mile though as it will give you instant readings so you can see what effect your speed has on the water in all directions.

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Hi John, it is Android speedometer.

Runs perfectly on my HTC Sensation and appears to agree with the car speedo, not yet put it against the plotter on the boat to see how accurate it is at very low speeds but it looks like it will be pretty good.

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I was thinking if i took the sat nav i'd have a constant " Please turn around at the nearest possible exit" ringing through my ears :P That app sounds really good, think that will be my best option as i always have my phone on me. Having to get a seperate gps seems more to look after and keep dry on the boat.

Thanks for all the responses :P

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Your 2hp outboard will give a maximum speed of no more than 6 mph on your inflatable, especially when loaded with two or three people and/or towing.

Your boat has a normal flat bottom. (as distinct from some that have inflatable keels, and can rise up slightly), and will have a maximum hull speed of about 5mph.

You could just break the 4mph speed limit with that combo, but the engine will really be at max revs, and drink fuel much faster than at 3/4 throttle or less, which should be a very comfortable and relatively quiet 4mph.

Non-planing boats have a scientifically fixed maximum speed, and the nearer you get to it, the power can be doubled or quadrupled, with little effect. The shorter they get, the lower that absolute maximum speed is.

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I was thinking if i took the sat nav i'd have a constant " Please turn around at the nearest possible exit" ringing through my ears :P That app sounds really good, think that will be my best option as i always have my phone on me. Having to get a seperate gps seems more to look after and keep dry on the boat.

Thanks for all the responses :P

You can turn off the sound on the sat nav,also you can watch your course on the screen,I used mine on a trip from Ranworth to Norwich on my 18 foot Norman,it was fine and it costs nothing if you already have a sat nav

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Hi everyone

I've looked on google maps and found a mile straight on the broads with a speed limit of 6mph. I was wondering if i stay at a constant speed and time how long it takes to cover the mile could i work out my speed? Lets say it takes 15 minutes (and 60 minutes = 1 mile) that i would be travelling at 4 mph?

Any advice would be greatly appreciated :P

Yes you can compute your SOG (Speed over the Ground) by using a measured mile, and I think there are actually some measured distances with marks on the Broads somewhere. Unfortunately you can't really learn much from this, as it will depend on the state of the tide..

But the main thing to remember is that the Broads speed limits are supposed to be there to control erosion and stop you bouncing around moored boats...

Both of these are linked to STW (Speed through the Water) and hence your wash.

So what do the BA do with their speed limits, they defined them as SOG as it is hard to measure STW unless you are actually on the boat....

You can get an approximate STW by looking at the revs, but for SOG then use a GPS, or GPS app on your phone.

(Warning: My normal mistake when coming to the Broads after going out on the sea is that I forget to change the unit setting on my handheld GPS from Knots to MPH!)

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