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Easy cheap build

It has to be easy and good value.

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Erfolg11/10/2019 20:44:56
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I have had a break from building a RMC Dornier 335. The reason being is fear and I have doubts if it will be robust enough for me.

I also have regrets, last week was our club auction, stupidly I missed out on a motor that I probably needed, just because I was not interested in a pile of others that came with it, they all went for in reality nothing. Otherwise this blog would have been about a Mercury kits Aeronca Sedan. Instead it is about a set of foam wings, that I bought for very little.

The wings came with a plan of one of favourite designers, David Boddington. On refection i came to the conclusion that it was not one of his better designs.

I then thought I personally value robust models, that I can fly in most weathers. No race horse for me, or Lutus Cars, rather a Shire horse, or BMW. Something that does the job, many see as boring, but solidly made, functional.

My wife has said I mean with myself, as i wont buy an expensive ARTF model, that cost thousands. I prefer a good value model.

So using the wings as the starting point, with the work horse in mind I set about designing a minimalist model,

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This is the basic design, as simple as I could make it, using minimal materials, as less is more. It owes a little to my NitroModels Do 335, in that I have tried to get the drag and thrust lines pretty much balance, to avoid down or other thrust.

I have started to create the servo lead passage in the wings on the "Neutral Axis". Which reminds me that a good few years back, when I was asked what I did for a living, i said I was an engineer. What sought came the next question, I am a Diploma or CEng I said. Ah, perhaps you could fix our lawn mower came the response, only my husband is a Professional, in insurance you know, practical things are not his forte. I sighed and said, i cannot fix lawn mowers, fridges are more my thing. Turned out he sold the thing called insurance.

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I have created a passage so far half way down the wing, using an old arrow shaft.

So its back to fixing fridges, until i have made some progress.

Edited By Erfolg on 11/10/2019 20:47:41

Erfolg13/10/2019 14:12:21
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As with many projects, I have considered a few issues and then made changes.

The obvious one is that the wing was cut with a slight amount of dihedral. I think that this unnecessary, with a high winger, that should be as happy upside down as normal. So I have made the aileron cable route go from one end to the other. The boring method i have used has worked with a high degree of accuracy, a little to my surprise. Initially i had twisted the arrow shaft by hand. But it was time consuming. I then tried using my electric brill/screwdriver, set for screws. This worked both fast and easier to control direction etc. A first for me.

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If you look carefully you can just see the arrow shaft at each end.

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This picture was supposed to show the passage way right through with the room lighting showing at the other end. It did using my eyes, not so the camera.

I am now joining the wing panels. I do not use GF cloth or anything like it, as it is pants to my mind. My hobby background is thermal gliders. I have a bible, which I refer to often, written by George Stringwell, titled "Thermal Gliders". Now George provides more methods for joining wing panels than you can shake a stick at. Pre moulded FG models, George provided all the answers you would ever need. In the case of foam cut wings veneered, Georges simplest way is essentially ply brace. The simplest does not even face the the ends with balsa sheet. Although George did shape his braces option to better distribute stresses into the materials. I have not bothered, as braces does a far better job of that aspect than most peoples GF bandage method. Although my brace does show what George advocates in Green.

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I just carefully mark out the wing both sides, work from either side as advocated, then open up progressively with saw blades.

I have now inserted the braces using PVA, this will take some time to set, probably days.

I have increased the height of the UC, as I realised, what I have drawn is fine take off, but limits the AOA when landing, probably preventing a good flare.

Erfolg16/10/2019 14:09:02
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I would not be surprised that many modelers also started building rubber jobbies, using a double edged, used Gillette razor blade. Not for me a single edged, NEW, razor blade. I made do, as I still do with dress makers pins of various vintages. Everything else relied on my teeth to chew through thicker balsa.

For years i have shown and registered contempt for those with a gadget for this, another for that. I made do. However in more recent times i have acquired various gadgets, often recommended in our posts.

Perhaps the first that really has improved both my quality of output in finish and accuracy is this £30 sander from lidl. I know at least one person paid even less.crying

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What is perhaps not obvious it has mitred the leading edge balsa perfectly.

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although the picture quality is pants, trust me, the joints are perfect, two 45 degree scarfs.

My latest Gizmo came in at £26, from HK. Previously for cutting strip wood I used a SLEC stripping device, it at best produced a passable strip. I have used it so far on some 1/8" ply, and to strip of the leading edge strips and 3/16" longerons. Now the longerons are perfect, just what the doctor ordered. Long ply pushes its capabilities. In case of balsa no problems.

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I have now started on the body.

Edited By Erfolg on 16/10/2019 14:09:41

Nigel R16/10/2019 14:16:15
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3394 forum posts
524 photos

Quick work Erfolg. Looks kind of Rival-ish for the fuselage. Should go nicely.

"My latest Gizmo came in at £26, from HK"

It appears to be a small table saw, correct me if I am wrong. I did not know they sold these.

I have made a captive blade stripper in the past, it works ok - providing the grain is perfectly straight. If the grain is not, the wood can compress behind the blade, leading to wobbly cuts. I have had to throw an otherwise usable sheet or two of wood because I could not keep the cut straight. The HK kit looks like a useful widget to have on hand for making strips.

Edited By Nigel R on 16/10/2019 14:18:49

gangster16/10/2019 17:10:37
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985 forum posts
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Erfolg. Easton Xx75 autumn gold. Also very useful for cutting holes in ribs for aileron/flap/etc leads and for lining wing bolt holes

Rich too16/10/2019 17:40:12
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Nice work yes

Erfolg17/10/2019 14:06:25
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11554 forum posts
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Nigel, it is a small saw table. In the past I have been put of some models, as they needed quite a lot of strip wood. As proportionally it is expensive, I have gone in for baulks of balsa. As I inferred, the SLEC stripper provided OK results after quite a bit of time and care.

I had considered the Proxon saw table, again I was put of by the price, my age, in that I would never see value for money from it.

Seeing the HK device for £26, I thought worth a try. I have been very surprised at how good a job it does and also so quick. My only concern is safety, the blade in use is not protected. On that basis extreme care is required, and constant thought of where my fingers are, and what could go wrong, to avoid injury.

As a builder I am slow, Sloth like, no pretensions to being a trades man.

As to what the model looks like. That has been dictated by the foam veneer wing. The body is just a 36" sheet, that is 3" wide. Being an ex engineer, I like straight lines, no fancy curves. As one of the Chief engineers said, in a meeting, when I hear you designers and architects talk about aesthetics and form, I see piles of money being stacked up and set on fire. Everything is simple with minimum wastage. If it turns out like something else, they just implemented the concept before me.

To keep both of the frame sides separate, I use bits of old plastic sheet, in this case a food packaging.

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the position of the support for the tray when finished is to accommodate any servo from standard to 9g types

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I was going to have a ply doubler that was full depth. I changed my mind on the basis it is the bottom of the model that constantly see the most forces and hence stress. I also pre-bend to make the next phase easier in my jig.

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Nigel R17/10/2019 14:48:30
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Thanks Erf. It sounds pretty good for our needs.

Build is proceeding pretty quickly despite your protestations!

Erfolg19/10/2019 16:56:49
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11554 forum posts
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I do not know about others, my building sessions start when I have nothing else to do and finish often when my old fashioned PVA needs to dry. There is another criteria, there is always 30 minutes spent on my modeling room when East Enders comes on.

I realise that these breaks are great, especially over night ones. As many of my decisions and thoughts occur whilst not fully asleep. Todays revolved around the motor. My drawing is based on the use of a Turnigy 35** type of motor. On reflection , I have a number of motors already, some possibly suitable.

 

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The extreme right motor is more than powerful enough, from experience. For the moment I have gone for the motor to the right. I know little about its technical detail, as it came out of my Parkzone Reliant, when the wing started stalling even at speed, and I found I could not buy a replacement one.

I have set up my jig and assembled the stick fuz in it. It is now out, at present I am sticking cross grain balsa across the top and bottom. Then with a reasonably stiff fuz i will stick on the side panels.

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this picture shows how the fuz has designed itself, being based on a standard 36" balsa sheet.

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Edited By Erfolg on 19/10/2019 16:57:33

Erfolg20/10/2019 16:41:41
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I now have a basic body.

My thoughts are now turning to both the tailplane and fin.

In essence the tailplane will have a fixed part of 18"*4". the moving bit probably 1" or maybe something a little bigger. Dependent on the % of wing area it comes out at. In the case of the fin, I am now thinking a triangle is probably the simplest, although, it all depends on what is left from the build so far and what I have lying about. I tend to like a bit of fin/rudder area, seems to little harm if generous, bit of a directional issue when a little small.

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Erfolg29/10/2019 15:16:32
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Although the weather is leapt forward to winter, I have had little time for any building.

I have spent the last week walking a dog, which i have been baby sitting, whilst my daughter No.1 went on holiday to Iceland. The grand kids complained on their return, it was so cold, no snow. I thought the name should give a clue. Any way two walks a day, over an hour each.. Still, I now have walked the beach in the depth of winter, seen the sea, in all of its, well, wetness.

I spent some time on the wing, comparing the nose section with NACA 0015, the drawing that came with the model. What ever the section is does not seem to be NACA, complicating matters the foam wing is not quite the same as the drawing. The complication being that a template made from the drawing, did not seem to fit, nor did a NACA print out.

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In the end I compromised and made a template, that was a blend of NACA and the section as cut.

I must admit, being historically a glider guider, I was obssive with respect to wing profiles. I have made a lot of wings, and have my own believes, as do most guiders. I know that Clary Y, although apparently similar to E205, they behave differently, E205 will penetrate with little height loss and will also loiter at low speed with little height loss. The percentage thickness being about 9-10%. I built heavily under-cambered wings, and flattish bottomed wings with a large camber. The experiments have gone on to thin percentage wings HLG 5 and MH32 for example. Played with nose radiuses and so on.

You cannot believe how much concern I have had with discovering the wing is 15%. I have built symmetrical wings relative recently.

This wing is NACA 9%

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Where if memory serves me well this is NACA 0008

I found that my ancient and now in bits KK Specter was NACA 0018.

I find that very thick wings require a lot of power to go fastish. Although the well rounded nose of the NACA 0000 series stall in a mush, seemingly holding high AoA beyond the section data suggest they are capable. In the case of the Specter, the high profile drag meant it did not accelerate much down hill.

As unhappy as I am, I have what I have. Time will tell how much of an issue the section really is.

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I had to stick on a extra piece of wood to get a good nose radius.

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All the major bits are now made.

Everything from now on is about the detail bits and assembly.

As a point of interest, counter to a lot of people, who fly aerobatics, I do not set my symmetrical sections at 0-0 to the tailplane, I set the wing 0-0 line at +2 degrees, to the tailplane and the body set at the position I want it to fly at under level flight. Otherwise the model will have to fly slightly tail down by about 2 degrees. It seems to work for me. With the convectional sections, typically set on the 0-0 line the section is still generating lift, which is not so with symmetrical sections.

Edited By Erfolg on 29/10/2019 15:17:18

Erfolg08/11/2019 19:55:58
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Right then!

The vast majority of all the basic detail work has now been completed.

There is a torsion bar UC, a steerable tail wheel. The mountings for the wing servos have been made and fitted. Wing tips shaped and glassed. I have given the veneered wing a coating of WBV, to aid film adhesion. The battery hatch just needs a little more work.

Most importantly I now have an idea with respect to the CG balance point. That is using either a 3s or 4s 2200 Lipo. It will need lead to bring the CG to the 25% chord point. I will run the basic design through a CG calculator, to get an idea how sensitive it would be at 30% chord.

The issue now is about covering the model.

I have toyed with using Christmas, present, type wrapping paper. I almost certainly will stick to China film. I have one major issue, that is my checker film has no adhesive on the film. I have only one pot of Balsaloc. I see that % star sell something called Coverloc, that appears to do the same thing, at a slightly higher price than Balsaloc sold for. Is there anything else that will do the same job?

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I will move onto a Lipo tray and Servo tray whilst I ponder the covering issues with respect to the checked covering for the wing and tailplane underside.

I will have to probably change my plans with respect to the servo tray. I had intended to mount the Rx at the forward end, with space to the side for a giro. The giro will eventually be for experimentation, as I want to build either a Gee Bee r1/2 or a QED, and feel a giro would make life potentially easier, providng longevity to the model. Plus a bit of knowledge and experience is always nice.

The table also urgently needs a tidy up.

Edited By Erfolg on 08/11/2019 19:58:33

Erfolg14/11/2019 19:01:48
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I used to think when I had reached this stage, covering, that the model was very near to finished. With the advent of ARTF models, I now know that I am some distance away.

The odds and ends have taken much more time than you tend to think. The motor hatch has taken much longer than i would have thought.

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It has taken me a day just to cover the underside of the model, goodness knows how long it will take for the rest.

Slow or what?

Bruce Collinson14/11/2019 21:15:13
442 forum posts

Erf, Solarfilm had Balsaloc fairly recently.

BTC

G194014/11/2019 21:52:43
3523 forum posts
1 photos

Airtek Hobbies sell something called MD Balsa Bond. No idea what it's like but I ordered some when I also orederd some Oratex for my Pup. It's at the bottom of the page.

Geoff

Erfolg19/11/2019 11:27:16
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I have had a look at Balsa bond, to my eyes it looks great.

Five Star also do a Balsaloc type product. Now they are in Bulgaria postage appears to be the bulk of their price. I use 5 Star Canopy glue, which works fine. I have also used their polypropylene to anything glue which works really well, given that gluing polypropylene to anything is next to impossible.

In the past I have used PVA and an iron to join balsa to ply sandwich, although my present PVA does not soften at all with heat. It seems some PVA is different to others. My present claims it is a resin, although I do not really know what a resin is, chemically, nor really what makes PVA, PVA. I am guessing in principal it is the difference between a Dead Mild Steel and one with Chrome or molybdenum in it etc.

Anyway I have been busy covering my creation (of Frankenstein) using checker from GiantShark (bought when closing the brand, and from HK.

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I have to confess, I complained that the GiantShark stuff had no adhesive. That was not the case. It is simply that the carrier film is firmly attaches, I had not removed it, on this model I have once I absolutely knew that is the case. It is incredibly well attached.

So the checker went on fine.

In the case of the HK stuff, incredibly good, although I used a higher than normal (for Solarfilm) temperature. It adheres very well and shrinks even better. Getting the stuff around radiused surfaces, can be done, even by me .

So why has it taken so long, because I am absolutely hopeless at film covering. What young boys and girls manage in southern Asia in a couple of minutes, takes me hours. In addition the finish they achieve is significantly better, possibly without trying.

Now it is back to assembly, although I am waiting for some servos ordered from HK, stupidly I put my order in with some propellors, which are on back order, to make an order up just shy of £14 and less than 200 grams.sad

Oh, the teddies all belong to my granddaughter, honest, we look after her on Friday nights and when the parents are on call. Honest.

Edited By Erfolg on 19/11/2019 11:32:19

Erfolg21/11/2019 16:49:05
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The model has now reached the stage where builders of kits/plans/own designs believe they can see the end of the road. That road requiring still many more hors of work and decision making.

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For the ARTF modeler, it is just a few hours of work, perhaps a few evenings.

I now can make a tentative stab at the cost. I have used 4 sheets of 1/8" and 1 sheet of 1/4 balsa, say £8. The wing cost me a £10 er, from the club bring and buy sale. The UC wire about £1.50 (from my SLEC purchase). All of the ply is offcuts, some from DIY projects. The film covering is also very low cost. The checker was from the GiantShark closing down sale. In the case of the red, that is a HK, 5 metre roll for the cost of a single metre sheet from Solafilm. In both cases far nicer to work with, being tougher and far more heat tolerant and incompetent modeler proof. On that basis, it must have cost about £30 to make. In reality I had everything to hand.

The last statement is not quite true, as I have ordered a new Rx from HK, still to arrive, brace yourselves lads for a tirade if it does not turn up soon. The other issue is I m waiting for some MG servos to come.

I am going metal gears, because I realise that all my servo breaks are me moving the model about. I am far more clumsy than I will admit.

The Lipo will be from not in use stock. I always now seem to buy more Lipos than i need to reduce the postal cost per item with respect to weight.

Anyway, there is still much to do, which includes servo plate, install servos, snake runs, control horns and so on.

Oh, will I pretty it up, in my case possibly not.

Edited By Erfolg on 21/11/2019 16:50:34

Edited By Erfolg on 21/11/2019 16:51:42

Erfolg28/11/2019 10:55:53
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It may seem that this build has stopped. Maybe lost momentum. Hmm maybe, there are reasons. Most significant is that this is a stage, I struggle with. The problem there are many options, each with their advantages and disadvantages.

My firm opinion, is that push rods have so many disadvantages as not to be worth considering. The centre body needs to be very stiff and light. Using materials such as large diameter carbon tubes, or arrow shafts, with very short stiff wire ends As I do not have the materials, and to purchase them can cost an arm and a leg. They are not for me.

I have used closed loop types in the past, on largish gliders, 100-144". The problem I have had is not just geometry, which has to be correct, it is the benefit of tension on the wire tracing. Unless the servo is ball bearing output support, the plain plastic bearing tends to wear, loosing tension, and the mesh on the gear train will become less than ideal. To overcome this I have in the past had an intermediate arm, which the wires attached to, then a short push rod to the arm. Messy, space and time consuming.

My preferred option these days is to stick servos at the back of the body, and also in the wings. There are IMO a number of benefits, Servos are often much cheaper than, snakes, push rods and gubbins, particularly where bell cranks are involved. Plus the weight penalty is often less or much the same.

So why have I gone for snakes on this build, primarily due to the use of old spare servos, which can be weighty, I expect to substitute some in time. Mainly I did not plan how and where to have servos at the back end of the body.

My first issue is that the snakes I had, I have not used the type before and did not know how to use them, Sounds stupid, but there we go. Ironically having posted a thread for know how, I have found that i have lost the outer, whilst sorting out the problem. It is in plain sight, somewhere, yet i cannot find it!

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The plain part to the back of the tray is for an Rx and a gyro. I have bought 3 in the past, never used one, I have no idea how to set one up. So, again i will be seeking help. I want gyro experience as I want to build a Gee Bee QED, or maybe a Gee Bee R1/2.

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I ma starting on the linkages.

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The Lipo area is finished, it could have been a tad longer, say 1/2-1" longer to provide more options for Lipo size above 2200.

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Any way, back to actually installing the snakes.

Erfolg06/12/2019 15:08:07
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11554 forum posts
1271 photos

FERTIG, ZUENDE

It’s finished. Well, that is an almost, I need to do a range check.

There is potential another issue, problem, the motor is only pulling 218 watts, on a 3s, the model weighs 1.7kg. I have looked at my other similar models, they are are pulling in excess of +300, many at 400 watts. The most obvious next step is to try a 4s, this could bring the energy drawn to just less than 300 watts.

My initial intention is to try the 3s, and see what happens. Although I am not expecting much. I remember my PT19 on low power, the take offs were a nightmare, after a long run, swinging hard left on lift of, with no real control. Loops had to be planned with care, and rolls were real barrels. Re-motoring, everything became not only easier, but non events.

As the real purpose of the model, is to try a gyro, to gain some experience, prior to building a Gee Bee R1/2 or a QED, the work needed to get the model trimmed out is a bit of a bind.

Erfolg07/12/2019 21:43:19
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11554 forum posts
1271 photos

I have been reflecting on the cost of the various bits and pieces, reflecting that the most I have directly spent was £6 for snakes. Not quite true as I spent about £20 on a Rx, but it has emphasised to me that to reduce cost, and also improved the design of the linkages, that mounting the tailplane and rudder servo at the back makes a lot of sense.

I now avoid snakes, push rods and 90 degree pivots, or snakes or torque rods to my ailerons due to slop, weight and to a degree costs, to drive them, it seems that there could be a similar benefit to the back end control surfaces. I just need to consider early on where and how to mount them.

The rest of the build is from stuff lying about.

 

Edited By Erfolg on 07/12/2019 21:44:37

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