Here is a list of all the postings Chris E has made in our forums. Click on a thread name to jump to the thread.
|Thread: Experimenting with Props,Motors and Batteries|
I guess we are all familiar with propeller design but in case we are not here goes with my (probably incorrect) thoughts.
A propeller can be thought of as a wing the rotates around a centre rather than flies straight through the medium in which it operates (as would an aircraft wing). An efficient wing has an aerofoil section with the lumpy side (technical term) toward the direction of desired lift. With a boat propeller this creates a low pressure area which means that the prop is effectively sucked into the vacuum as well as pushing the water back because of the blade pitch. This much more efficient than relying on blade pitch alone but does tend to make the prop directional as that which increases thrust in one direction reduces it if reversed. Aermodellers know this because they have sorted out numerous beginners who have fitted their props backward & wonder why the model is underpowered.
As a result of this the Graupner 3 blade plastic scale props produce roughly twice the thrust going forward as they do in reverse for about the same watts input. They are actually very efficient in one direction & fairly inefficient in the other.
Half power in reverse has always been enough for me although you can never have too much when trying to stop a very heavy barge which has got a bit of momentum going. A 200lb barge takes a bit of stopping.
Plastic props are far from being rubbish - or at least the well designed ones are.
I have always found Graupner plastic 3 blade props to be good. They are low pitch which means that you can use a larger prop which works well for tugs. A same size brass prop will deliver more power but it uses a lot more power to do so. Plastic props are also cheap which means that I can experiment to get the best one.
I agree that there is less thrust going astern but I have never found that to be a problem. How much power do you need for a fishing boat going backwards? Crash stops just look wrong.
Edited By Chris E 1 on 07/07/2019 08:18:33
Edited By Chris E 1 on 07/07/2019 08:19:11
|Thread: Hello and what have I started?|
Thanks for that. I wasn't saying that the hull was finished I was asking you to clarify whether you would glue steel to a finished painted hull & I have gathered that you would. I would prefer to also have a mechanical fixing which becomes more important the heavier the weight gets.
Edited By Chris E 1 on 06/07/2019 08:04:52
So first you must stop the keel rusting & then glue it to the hull.
How do you achieve all this including is the hull fully finished before you start?
|Thread: Plans in the archive|
I know that the free plan is excluded from the digital subscription and the archive but is it really so difficult to include a reduced size version so that we can at least see what is going on?
|Thread: Huntsman31 SLEC Model Boats Mag|
Was the satisfactory performance of the model in the current issue with a 2S or 3S battery?
|Thread: Just got a camcorder|
I too enjoyed your video. Again it is a branch of modelling that I do not undertake but that does not mean that I am not interested.
I might also congratulate you on your camera work. The model was easily visible, in focus and not subject to those sea sick violent movements that so many videos exhibit. A few captions or a little narrative would be even better.
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