By continuing to use this site, you agree to our use of cookies. Find out more

Member postings for Chris E

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
07/07/2019 12:02:41

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.

07/07/2019 08:16:53
Posted by harry smith 1 on 06/07/2019 06:14:45:

Hi All

Decided to use one of my Hellen fishing boats as a base for this project.

At 860mm long, beam 250mm and 14 pounds it requires of power get the old girl moving!!!

I first used the original plastic 60mm 3 blade on a rock crawler(540) 55 turn with a 7.2 volt Lipo battery.

Good forward speed, but reverse was total rubbish............................

mainly that plastic props are rubbish..................................

Harry Smith

 

 

 

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?
06/07/2019 07:48:54

Ashley

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.

Thanks again.

Edited By Chris E 1 on 06/07/2019 08:04:52

04/07/2019 12:47:56
Posted by ashley needham on 03/07/2019 21:23:39:

External keels work very well with small warship type hulls, if you don’t mind a bump underneath the hull.

A couple of mine have a strip of 5mm steel glued in place and it is just the job.

Ashley

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
21/01/2019 12:33:34

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
17/11/2018 20:55:53

Was the satisfactory performance of the model in the current issue with a 2S or 3S battery?

Thread: Just got a camcorder
15/08/2018 12:37:00

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.

Magazine Locator

Want the latest issue of Model Boats? Use our magazine locator link to find your nearest stockist!

Find Model Boats!

Support Our Partners
SLEC
Coastal Shipping August 2021
Nylet
Sarik
Premier March
Restorers Wanted
Pendle Boilers
Shopping Partners
Social Media

'Like' us on Facebook

Follow us on Twitter

Pin us on Pinterest

Member Contributions
Distributors of Model Boats for our overseas readers
Highlights

Make sure you never miss out on the latest news, product reviews and competitions with our free RSS feed

Make your own contribution to the Website

We welcome well written contributions from Website members on almost any aspect of Model Boating with a particular emphasis on practical hints, tips, experience and builds.

In order to maintain a consistent standard and format, all suggestions should first be sent to me by Personal Message for approval in principle. Only a very limited amount of time is available for editing contributions into a suitable format for placing on the website so it is important that the material is well presented, lucid and free from obvious spelling errors. I think it goes without saying that contributions should be illustrated by appropriate photos. I shall be happy to give advice on this.

The Member Contribution area offers space for short informative mini articles which would not normally find a place in Model Boats magazine. It is an opportunity for Website Members to freely share their  expertise and experience but I am afraid that virtue is its own reward as there is no budget to offer more material recompense!

I look forward to receiving your suggestions.

Colin Bishop - Website Editor