MIKE S

Our HHMFC  Shenley Flying Field has adopted the tiny Multiplex Fox as a small cheap model which starts life as a chuck glider and ends up as an RC electric aerobatic fun plane.   Just buy the chuck glider, hollow out some of the fuselage, fit a couple of 2,5 gram servos and a small outrunner ESC and  lipoly and you are ready to race around pylons about 100 meters apart (on a fine day!)  Great fun and not much to lose if you crash. We use 2.4 radio. The secret is to keep the weight down to a minimum. Variations can be almost every part fitted, servos from an MSX Helicopter possible. Very competitive with lots of ideas for a faster version without changing the basic structure or shape.   http://roys-rc-tv.webs.com/fox.htm.Edited By Chris Card - Moderator on 05/05/2010 19:31:16

Over the years I have used a number of ready made plastic undercarriages. Most are made from laminated glass fibre mat or Carbon Fibre sheet. The problem with these are a weakness at the bend. The strength of both carbon fibre and glass fibre is in the strands, when these are woven in to a sheet, they give strength in all directions, For an undercarriage you need the strength against bending. Also when a number of sheets are laminated , they often split apart at the bends. One can buy fibre glass strand, like rope. If you laminate this lengthwise in a mould, plus a few strands across, it makes a very strong assembly which should take a lot of hard landings. Remember that when a plane lands on rough ground the undercarriage tries to bend backwards with considerable force and leverage. Think how much leverage you can apply to a 40cm spanner. Many ARTF models have a simple plate glued to the fuselage sides. It has no hope of resisting the bending force from a hard landing. Reinforce it with verticals up the inner sides or bend up a metal "U" to spread the load.

Tony TTowlieFirst have a look at the YouTube bit which shows our Shenley field.  : http://www.youtube.com/watch?v=ET_4clwewqw Tony T. Puttenham is the nearest field to Milton Keynes, very near to Tring, just South of Aylesbury. No YouTube of that site, but it is very well liked by the people who fly there. Towlie, Your best site is Shenley, just off the M25 and near to the Mosquito Museum.  My problem is that we are having an EGM later this month to decide whether to remain as HHMFC with two fields or split in to two clubs with their own committee, assets and funds.This has come about by a few at Puttenham complaining that they are subsidising Shenley. Shenley is a much bigger field and has open space all around, but it does cost more. On the other hand it should have more members which keeps the cost down.  Until the decision is made whether to stay as we are or split, I can not do more than put your names down. What you can do at Shenley is come along as our guest and fly a few times until the decision is made. It looks likely that Shenley will form a new club, but will certainly keep the existing field and facillities    Edited By Timbo - Moderator on 09/10/2009 22:40:41

The Hemel Hempstead Model Flying Club at present has two sites. Both kept in an excellent state, one north of Hemel Hempstead about 12 miles and the other larger main club site at Shenley, 10 miles to the east. Local to Hatfield, St Albans and North London. To avoid having to split up the club, we are inviting new members in the Shenley Area. to balance the costs between sites.  The Shenley site has a large flat mown patch about 100 mtrs x 60. Access to the site which is on the top of a hill, is by private road. We are well away from any houses, roads or noise worriers. The sky is open and there are no obstructions.  A container is used as a mower store and clubhouse.  Restrictions are minimum. A max of 45 cc and no jets yet (insurance) We are not BMFA and do not have certification levels. All are welcome. Beginners get help and can use a buddy box. Solar Panels will keep large batteries charged for Electrics and soon there will be an automatic weather station which you can phone for the site conditions.

Craig, I have been considering the Lander unit for some time. Is the fan aluminium or just a similar plastic moulding? The outer case while being stronger in aluminium, would not improve the thrust. I have bought and played with many EDF's over the past few years. Most have had poor design of fan. Some have been near impossible to balance. I saw many aluminium units at Cosford last weekend and was very tempted, My best performer is an F16 which came already fitted out. It has such a tiny motor and fan, that I can not believe its performance. Straight up even with the weight of a 2200 3 cell.  I have a lot of pictures on Picasa 3, but have not managed to get them on to this site. A quick how to would be interesting.

I did mean tail heavy, not nose heavy. The reason for fitting the AP90 EDF was just that I had one and bench testing showed it to be good. It was not a lot of trouble fitting it in and I do like to experiment. I am using a 3400, 4 cell LiPoly to give more weight to the nose, but not enough.  My previous two A4's have standard size EDF and fly quite well. Fitting the larger fan, has resulted in extra weight, compensated for by the extra 34 sq ins area from the inner wing extensions.  I may try one of the new Aluminium EDF,s from BRC. 

My GWS A4 is now completed and went out for it's first flight.Not a great success. A good launch sent it away but the nose went straight up and I had a Jet Hang, before closing the throttle and flopping down on the long wheat over which we launched. Every indication to me that it was nose heavy.Second attempt after moving the 3400, 14.8 LiPoly forward as far as possible, was no better. Another drop in to the wheat. Lead weight added to the nose, this time it managed a flick roll in to the wheat. Broke the nose off.Back to the drawing board. Possibly move the EDF forward another inch. Then a lighter LiPoly.  Just in case of disaster, I did take some photo's of the A4 suspended on a string over our patch, then removed the string by a clone brush. Looks good flying over its own shadow. Now have to calculate the C of G. It was exactly where GWS placed it, but it still went nose up after launch. My extension wings might have moved it a bit, but I thought it would fly. Power / thrust from the AP90 fan was enough to hold its own weight.  Went back to my re-built EF 16, which flies a dream.       

My A4 Skyhawk is now finished and readt for it's first flight. After painting with emulsion and Japlac colour, I covered the whole underside with one piece of garden fleece,  Ronseal Diamond Varnish holds it on and makes the whole plane harder as well as covering the transfers.   Looks good and is certainly an improvement over my first and second version. The larger EDF (AP90 with HET motor) gives out plenty of thrust and may take off from a dolly.

Hemel Hempstead Model Flying Club (HHMFC on Google)   Cant get a better field with superb open skies for miles and views to keep a wife happy. We also welcome new members. If you prefer we have a smaller field 12 miles north of Hemel, but an easy drive. Very friendly. You can fly without certificates which we do not have. Fly for fun and enjoyment or just come and sit out watching others!

Any serious flyer or beginner could do worse than contact The Hemel Hempstead Flying Club. (Google HHMFC) We are about 100 members, flying anything from indoor up to 40cc. We have two excellent fields, one 12 miles East of Hemel Hempstead and one 12 miles North. Both are grass patches, but kept short.  Both have parking and a container to store your bits or get out of the rain! We do avoid competitions and complicated regulations, although we are fully insured. We do not recognise flying certificates, but have no objection to them as long as they do not spoil our fun. Fun is what we do try and achieve.  Many members are now changing to Electric and to 2.4. So if you are looking for a club, look up HHMFC in your browser.

Yes I used to fly on Bovingdon. Recently I did some work at a painters on the airfield and was told that there are a few peole who fly there. I was invited to bring my models and fly from the area of concrete outside the factories.   As Chairman of Hemel Hempstead Model Flying Club, a new site is not necessary. We have two excellent fields one at Shenley and one at Puttenham. Shenley has the best view over the countryside to St Albans in one direction and Canary Wharf in the other. A grass patch, but aboyt 100 yards by 50, kept short.

I am now completing my 3rd GWS Skyhawk. It is such a complete and well made kit for the money.It even contains the extension leads, Y lead and lots of plastic mouldings.    My first one was built exactly to the instructions, using the supplied EDF. A long high power motor was used. Unfortunately the impeller first supplied was an early design and lacked a backplate which is not supplied, although my third kit still has the old impeller. A call to JP Perkins did get replacements.   This model flies very well. It has no undercarriage, but gets away from a hand launch at quite low speed with no problems.   My second version had the undercarriage fitted. It fractured, being very brittle on the first flight. New slightly thicker struts were made and lasted quite well. This one took-off from short grass in 30 feet. and flew well, but not as well as the one with no U/C   My third version is fitted with an AP 90 EDF and a HET motor. Much more thrust. The fuselage had to be ground out to take the large unit, but this is fairly easy, finishing off with sandpaper wrapped around a roll of tape the correct diameter. The hatch also has to be opened out and slighly modified to fit with a tongue at the front and a screw at the rear.   Because of the extra weight of the AP90, I moved the Unit forward about 20mm to overcome a tail heavy situation. I then decided to increase the wing area by making two balsa wing extensions 2" wide to fit between the outer foam wings and the fuselage inner wing. This added about 64 sq ins area, for very little extra weight. Simply made from two ribs each, glued to 2" wide, 1/16" sheet balsa skins. 3/8" hard balsa spars feed through and fit in to the moulded openings in the fuselage and wings.  The outer wings are sanded to gie 1/2" dihedral at the tip and glued to the extensins and spars.   Not yet completed, but a run of the EDF on 14.8 volts demonstrates very good power to weight, just able to hold its own weight when vertical. That and the extra wing area, should make it exciting to fly, without being too fast and too heavy.   I will let you know after the first flight.  

Anyone tried to strengthen the foam surface of models like the A4 Skyhawk by GWS? I have built two and what superb ducted fans they are. Unfortunately they are also easily dented or bent, mainly hanger rash.   I am about to build my third, but intend covering the foam parts with water based varnish and garden floss. I will lose some detail, but hopefully will gain strength.

1. With all the new interest and technical development, my selection would be a Ducted Fan 1. Gloster Meteor. Using a pair of Hyperflow or cheap 70mm fans. Built to a minimum weight with carbon fibre reinforcement 2. Vampire. 48" span, one good ducted fan 3. Canbera.  A pair of TowerPro or similar fans with good Brushless motors.

We are getting on with testing EDF's and learning something every day. Using the 5.1Kv motor in a TowerPro 69mm fan, resulted in the best thrust for this size unit, but drew far too many amps, about 50. The 3.9 Kv motor reduced thrust, but not by much and the amps came down to 30 maximum.  Static thrust with the intake rings on averaged 23 ozs. The much smaller Hyperflow EDF's with Ammo motors, bought direct from Tower Hobbies in USA are superb little units, giving 16 oz thrust at 200 watts. I am using two in a scratch built Gloster Meteor. In the air with good design of ducting, I expect 23 oz thrust. My next phase is to get a data logger to record all my tests and produce graphs. One thing I have learned is that using LiPoly's for the power on the rig is not impossible but does not produce consistant results as the voltage drops quite fast and one has to charge up for every test. A Large car battery with a heavy duty charger provides a constant voltage and allows more testing with consistancy. Another finding is that very careful balancing of the fan and nose is worth doing. 

Scott, You are right, there are now so many EDF's on the market. Most of the cheap ones are flimsy and with fans that do not have the correct pitch change from hub to tip, resulting in uneven flow over the fan diameter. Some are fairly good, but have moulded fans in ABS which does not like 50,000 rpm. Some are very expensive and look like they are made from drainpipe. A friend has just bought the rolls Royce of EDF's and it looks home made. The fan is beautiful but the shroud and other bits are very amaturish, although with the correct motor they claim to produce the thrust. Motors are another learning curve. Does one want a fine pitch fan with a high reving motor or a coarse pitch with a low revver? My tests do indicate that the best for static thrust is a fine pitch (like a propeller) with a high rev per volt. Then if the motor does not have enough power to reach the high revs, due to too large a fan, it is inificient at take off, but might be very fast in flight. Prices of motors for EDF vary from a few pounds up to hundreds. Once in the unit it is difficult to know which one you have spent your money on. Hence the need to test! All costing quite a lot though. All for the hope of building  a Gloster Meteor which can take off! 

I know that the ducting has a big effect on thrust, but for the time being I am only doing comparison between vatios fans and motors of the same basic size. So far I have recorded the highest thrust with a TowerPro EDF from RCM Direct using one of their 5.1Kv inrunner motors. This at 1 lb on my digital readout and 210 watts. LiPoly at 10 volts. The same fan with the RCM Direct 3.9Kv motor only gave  9 oz thrust. A cobination unit again from RCM Direct but with an outrunner built in was a poor 6 oz thrust. My test rig has not been calibrated yet, so the thrust may be reading low, but the watts and volts are correct using a quality in line unit. This does not matter much as I have proved that the 5.1Kv motor in the TowerPro unit are my best option to fit in my North American Fury, which failed after one flight with a WemoTech. The fan broke up with the 5.1Kv motor.  More work going on. Results later. New Hyperflow EDF's with AMMO motors on route from USA.

Finished off the Thrust Test Bed now. All rigged up and ready to go. Unfortunately I have had a blade off my Airpower 70 unit and am waiting for a new fan from the supplier. I have two TowerPro 70mm units, one with 3.9Kv motor and one with 5.1Kv. It will be interesting to see which one produces the maximum static thrust. These are good cheap units, but do need a lot of balancing to make them run at a smooth full power. Airpower EDF's are much better feeling and have a better motor adapter. Next to try are the HyperFlow units from Great Planes, but so far I have not found a UK Supplier.  I would post the photo's, but have not yet discovered how to achieve this. 

Having now scratch built a number of EDF planes, some a failure and some a great success, I decided that what I needed was a test rig. I built up a static frame from MDF and a floating EDF holder which sits on flexible strips allowing it to move along the thrust line. Various EDF units can be mounted in a vertical plate. To drive the EDF I used standard bits such as an old 60amp ESC, an old radio receiver and either a LiPoly or 12volt car battery. To measure the thrust I bought a £9.99 kitchen scales. (Robert Dyass) Super bit of kit. Dismantled it had a 5Kg load beam connected to a control pnel and LCD display. Cut up in to separate bits, it proved possible to fit the load cell at one end so that the floating EDF holder pushed against it. The panel was now cut to only be what was needed, the two AAA batteries were mounted underneath in their holder cut away from the main moulding.    Reslults will follow later, but first test runs with an Airpower fan unit have shown that it works!