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Member postings for Dave Hopkin

Here is a list of all the postings Dave Hopkin has made in our forums. Click on a thread name to jump to the thread.

Thread: Pedantic
25/02/2018 23:54:01

In terms of T'Interweb "Store" is the accepted term for an on-line shopping portal (as in Appstore) so I would suggest it is appropriate and since this thread is entitled "pedantic" then I feel justified in pointing out the origin of the word is old french....

Middle English: shortening of Old French estore (noun), estorer (verb), from Latin instaurare ‘renew’; compare with restore.

Thread: WW1 Aircraft detailed close up photo collection
25/02/2018 23:39:05

The Vintage Aviator is a replica aircraft manufacturer that has created many WW1 aircraft to exacting standards as I am sure many of you already know, I recently contacted them asking for some specific details and they sent me a link to the photo collection of their official photographer James Fahey

There are some fabulously detailed photos of all sorts of mouth watering subjects here....

**LINK**

The Vintage Aviators web site is here

**LINK**

If you are into WW1 string bags its well worth a look!!!!

Thread: What battery
23/02/2018 18:00:13

The intention was not to scare you, but without details of the plane its an impossible question to answer and rather than just ignore you I was trying to illustrate the variables

if the plane is 800g then you will be looking for around 150Watts

To get 150 Watts from a 3S lipo then you will be pulling around 12 Amps max - so say 6 Amps average

So your 1000Mah lipo will give you around 5 minutes flying time - give or take

So its a reasonable set up so far

What motor and prop have you ordered?

23/02/2018 17:20:13

There are many factors that affect "which battery"

There is the question of size and weight - the bigger the battery the bigger and heavier it gets - obviously in any model there is a physical limit to the dimensions of the battery, there is also the question of weight - the Lipo is one of the heaviest things in the model so it will have a dramatic effect on balance - in most models the battery needs to go as far in front of the desired CoG as possible to avoid having to add (dead) weight to balance it - most people if they need more weight up front use a bigger capacity battery rather than lead

Secondly there are the electrical questions? Duration of your flight and the ability of the battery to supply the current demanded by the motor/prop combo

To estimate duration we need to know the current drain - that can be established roughly by taking a reading of the amperage at half throttle - divide the battery capacity by the current drain and yo have a rough estimate of duration of flight - the bigger the capacity the long the flight

The current draw by the motor will vary with the prop you fit, a small one will use less current but provide less thrust, a larger one will give more thrust but use more current

So where do you start????

We have a 3S 1500 Battery - you have ordered the motor, esc and prop - so when those arrive the best thing is to set up a test bed - fix the motor to a lump of wood (not balsa) and shove it in a vice- connect up the radio and bing in the ESC and test the motor WITHOUT the prop, you will need a WATT METER to check the current draw is below the ESC Rating with the motor running- now fix the prop and again read the current - it will have jumped up a LOT.... make sure that at full throttle there is still at least 15% headroom between max current drawn by the motor and the ESC rating

As a rough (very) guide to power you will need (ish) at least

100 Watts per Lb of model for a typical training/sports model

If you motor/prop/battery combo gives at least that - then great, if not one of them has to be changed

Thread: lettering and decals
22/02/2018 18:03:42

dscf1077.jpg

Thread: What are the rules?
19/02/2018 22:56:49

Without vanishing down a rabbit hole of aerodynamic theory

For practical design look at aircraft that fly they all have different design objective like heavy lift, STOL, pure speed, endurance, aerobatics etc etc - so that I would suggest would be a starting point "what sort of aircraft do you want?"

Once you answer that question then look at full sized aircraft with the same design objective (that worked!) and look at what makes them successful in that role - use that as a starting point

The decide how big you want your model think about things like storage, transporting it, power its liable to need - roughly similar models can give you a guide as to possible weights and power requirements

So by now you have some rough parameters that will limit your design

Thread: Electric Cars.
18/02/2018 08:34:25

At the risk of going off-topic... I saw an advert for the new leaf and it said it only ha ONE pedal

how the hell does that work.............. emergency braking????

16/02/2018 16:26:49

Maybe this is the way forwards....

Japan already has 80 Hydrogen fueling points and 42 in California

**LINK**

15/02/2018 22:02:36

All well and good Percy for short/medium distance journeys - but if I want to go on holiday with the car i need the legs and fast refuel times liquid fuel gives me (and that doesnt have to be oil based liquid) - exchangeable battery packs might be the answer (if they standardise them) but even fast recharge points are going to mean a lot of dead time

15/02/2018 21:45:34

I still think that the "tipping point" for electric cars wont happen until the recharging time can complete with the refueling time of conventional cars - perhaps exchangeable battery packs are an answer or as I suspect are electric cars going to be betamax/squarial technology and ultimately rendered obsolete by something like liquid hydrogen powered cars?

Thread: Max Thrust Riot
15/02/2018 21:37:55

It also happens when you haven;t allowed the ESC to "learn" the TX - to do this:

power off the model

Remove the propellor

TX on and throttle open to full

Power on the model

the ESC should bleep once per cell as it senses the Lipo then give a longer bleep

Reduce the Throttle to its lowest point

Power off the model

Power up the model and (fingers crossed) it should work

If you have Futabla you may have to reverse the throttle

Thread: Sign of the times - funnies
14/02/2018 22:13:17

Had a college over from the US and he wanted to see the sights then back to ours for dinner- as we were opening the front door he was saying "Gee everything in your country is so small, the houses, the cars...." then he saw the wife - that shut him up

14/02/2018 22:11:08

She phoned me from work and said "three of the girls in the office have had big bunches of flowers delivered, they are gorgeous"

I said "That's probably why they got flowers"

14/02/2018 22:09:36

you just cant please women...

Got the Mrs 250 flowers for Valentines Day

So what if the spelled out "Granddad"

Thread: Heathrow Aeroplane drops deadly item
10/02/2018 21:32:31

And don't lick yellow ice.... or "Frozen Chocolate"

Thread: Re: Death of IC
03/02/2018 20:07:03

With the assumption that batteries will continue to improve in energy/weight ratios I think that the 40 to 60 size will become increasingly rarer to see - they wont die as such as there are so many in regular use but I would expect to see sales of the lower end of IC to dwindle considerably, but I cant see electric making much ingress into the larger end of the IC Market place in the short or medium term unless there is some dramatic change in the available technology, but that technology change will arrive at some stage and allow some ingress of electric into the larger end of the market

31/01/2018 18:44:34
Posted by John Stainforth on 31/01/2018 18:38:02:

Dave,

Glow fuel is not a fossil fuel - it's comprised of methanol and nitromethane and some oil (which could be non-fossil).

 

Nitromethane is produced by a chemical reaction using propane and nitric acid - propane is a natural gas, ergo a fossil fuel

 

Edited By Dave Hopkin on 31/01/2018 18:46:02

31/01/2018 18:42:04
Posted by Jon Laughton on 31/01/2018 18:18:51:

Hey Hoppy! Long time no see....and you know you really want that two stroke model! devil

Hey Jon

I might well be tempted but SWHMBO is most definitely not a fan and I know what battles are just not worth fighting!!!

31/01/2018 18:14:36

Is IC doomed? Probably but not for a long time yet! Reasons

a) Its a fossil fuel based so running costs will only increase over time faster than electricity will

b) Its essentially a static technology very little R&D money is invested in IC these days compared with the billions being invested in battery technology - in time that will filter down to us flyers and power/weight ratios of electric sets ups will get better and better and at some stage offer the same endurance as IC

c) The vast majority of new blood to the hobby comes in now on electric power, yes a proportion will convert/dabble in IC but I suspect the majority wont

Thread: The Warbirds Replicas Macchi C.202 is Landing!
23/01/2018 22:58:38

If you tear the brown paper rather then cut it the overlaps are far less visible

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