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Member postings for Erfolg

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

Thread: Miss Deeds or 1/4 semi scale Cassutt
19/09/2019 11:12:11

Well, Whilst some bits are drying, I thought now is a good time to show the next stage. As I was pressed for time (I have only the one).sad


For this model I made some stick on templates. The top of the turtle back remains the same as the PM plan, as is the bottom. It is the shoulder area that I widened to a more scale dimension, of the narrowest reference I found, whilst reading and searching about Cassutt builds.

I was tempted to produce a more rounded top, to the turtle back, as it appears that most if not all full size have a bent piece of ply wood in this area. In the end I decided to keep things simple as the PM drawing.

In my opinion it does indicate what you can do to many of Peters semi scale designs, although at our own risk.

Rather stupidly I have removed the uprights from my body jig, as they were getting in the way of checking the tailplane to wing alignment.

This is what it would have looked like although in this case a TH Clean Sweep.

Perhaps I should mention there is another slight deviation from plan, in that I intend using a plate type undercarriage , as per full size. On that basis I have a ply section in the base a little wider than Peters, and some ply spreader plates on the inside to distribute the forces a little differently to Peters Torsion Bar arrangement. I do find that torsion bars work really well. My oldest model at 40 years old has them and flies most weeks.


Th real thing now!

cassutt iiim racer - untitled _ aviation photo #1621078 ___.jpg

As you can see this version has something similar to a torsion bar set upcrying


and one with a broad chord UCsmiley

Edited By Erfolg on 19/09/2019 11:26:21

Thread: Werewolf free plan
19/09/2019 10:49:49

Yep, It is a me two model with me, want one, just have not got around to build one.

I once hoped it was going to be selected for the mass build for Greenacres Fly in. Alas it was not chosen. Then I hoped that the Swap Rat would be chosen, alas again, not to be (another simple build) Again a bit of a looker..

It always reminds me of the Peter Russel 334G and a bit like a Fw 190.

It has to be a very good choice, as all of Peters models fly well.

Thread: Battle of Britain day
18/09/2019 17:55:44


I am particularly looking to get away from my daughters dog, my daughter I can live with, but the dog, the sooner it goes the better.smiley

Edited By Erfolg on 18/09/2019 17:56:06

Edited By Erfolg on 18/09/2019 17:56:24

Thread: What replacement for brushed
17/09/2019 20:13:25


I am really pleased that you have drawn our attention to these motors, although I now mostly fly sport and scale, I can see these motors being really useful in a model I will be assembling with a radial cowl. Previously I have used the Turnigy high torque inrunners, as these no longer seem to be stocked, it is a potentially excellent solution.smiley

As for breaking props on a few hundred watts, I have only manged that when using Chinese folding blades. For folders it is Aeronaut or Graupner. 200 watts is nowt, as we say up here in the North. Start talking Kilowatts then some will start waking up.

Thread: Battle of Britain day
17/09/2019 19:55:20

We have bought our tickets, booked accommodation (in some university dormitory).

Driving down on Friday, attending on Saturday, (had to cut it short, have another must do engagement) then driving home on Sunday. That will be a trivial +9 hour drive in total.

But I am sure it will be worth the effort.

Thread: Miss Deeds or 1/4 semi scale Cassutt
17/09/2019 16:32:03

This is perhaps an extreme example of using blue foam then glassing it.



If you look at the tail pipe you can see the blue foam still. I must admit that i did not try for a good finish, as the full size was very rough, in all aspects.


17/09/2019 14:31:12


The use of Blue Foam is certainly not a new idea. Perhaps the most well know is Chris Golds, who would PVA the finished form.

In my case I use 1.5 oz Glass Cloth, it makes for a much better finish and dinge resistance. I mainly just use one layer although I have been known to use two, applied together.

My technique is to mask the balsa area, with masking tape. I then lay up onto the tape with a slight overlap. In the case of the Cassutt I did the whole tip in one go, as the cloth draped over it very well. I apply about 4 coats of WBV, having left the first coat for a few hours, then rubbed down slightly. In this case it was not really needed. The next 3 I do when touch dry, about 30 minutes although an hour is probably better. When dry, leaving overnight. I just trim through the cloth into the balsa end rib. Then I just peel of the masking tape, together with the glass overlap.


I perhaps should have shown the template I use to form the nose. Again not rocket science, although in this era, where very few build, the methodical stage by stage approach in obtaining acceptable accuracy is not as commonly known.

I believe that the secret to the accuracy that good tradesmen achieve, is more to do with a systematic approach, rather than just an inherent skill that revealed itself when they picked up the first tool

16/09/2019 20:26:14

Just to clarify, the wing still has the equivalent of a "D" box, the spars are separated by shear webs. It is just that the back end of the wing is sheeted, forming a further monocoque type section. The real purpose of fully sheeting is to more closely replicate the finish of the full size, non of that miniscule sagging between cap strips. Although if the full size had been a sown on rib and covering, i would have gone the capstrip route.

Anyway, now i have the Blue Foam (Dow Corning Floormate) wing tips with glass cloth, using Ronseal Hardglase as the adhesive. It makes for very resilient to denting covering. With WBV, my better half never complains, doe not even know what I am up to.

Thread: Autumn is been flying ?
15/09/2019 21:07:41


Our track is almost exactly 0.5 miles long (it is slightly longer), down hill. It is a long, long way. Of course up hill when leavingsad

As you enter the track, a decision has to be made, is there a hint of another vehicle, if so, is it advancing, or stationary. As the track is so narrow, with a field to fall into on one side and a hedge on the other, you need to be sure that you can make it without meeting anyone in the middle.crying.

Edited By Erfolg on 15/09/2019 21:08:08

15/09/2019 20:14:34

Autumn is here, the track to the field has the fist signs of mud.

The fracking protestors all seem to have gone into hibernation. their protest signs piled up by their ramshackle cabin. Even the police seem to have disappeared, much to the relieve of the rate payers. Now a flare can be seen above the site, are they measuring flow rate?

Giant tractors complete with bailers, trailers hurtle along the narrow lanes.

Yep, it is almost certainly autumn.

I have been down to our field three times over the week end. Every time flocks of hundreds of Greece have flown over. Some at great height, one flock at less than 400 feet. The total numbers in the thousands. Yet on Saturday, house or sand Martins were to be seen,

As for the flying. not great, every day it has been cross wind to the strip, less so on Saturday. My trusty delta, has become less reliable, requiring maintenance, the it shed a blade, for a moment I thought I had five of them, as i struggled to restrain and initially comprehend what was happening. Still back in the air, with temporary small props. I am now waiting for the best size to arrive from China. Did I mention, we no longer have a MS within a 30 mile radius, now at 60 miles,

I flew my Albatross Dva, which flew great, until I came to landing. With cross win, better not get into details, never the less it survived.

With the weather deterioration, I am often Billy no mates, which will probably continue now until spring.

Thread: Miss Deeds or 1/4 semi scale Cassutt
15/09/2019 17:54:58


That is certainly the case, but there is no substitute for incompetence.

Whenever I know I have cracked it, I prove that my confidence is misplaced.

Which again points to the benefits of PM designs, robust!

Thread: Thinking aloud about Spits...
15/09/2019 17:51:33


What surprises me that in WW2 many designers realised that boundary layer was not the best place for an inlet, come the Jet age, for engine intakes it seemed to have been forgotten. Or perhaps they thought different criteria applied to jet engine intakes.

As Patmacs link indicates, by the time you get passed the nose on a propellor aircraft, the air is seriously turbulent. May be they thought without a propellor, everything would be laminar with a nice velocity gradient?

Thread: Miss Deeds or 1/4 semi scale Cassutt
15/09/2019 17:40:50

I think it is worth mentioning that on something such as the Cassutt, the concerns we might have with respect a large glider wing+100" with regard to tip weight, they are far less significant with Low Aspect ratio wings. I will probably expose the wing to greater loads in a less than text book landing (catching a tip, flipping over) than from flying,

15/09/2019 17:10:18

Denis what are DF?

15/09/2019 17:06:47

My spars are vastly over sized, with respect to the forces you would expect from flying. There is a good reason however, the reason being that is what I have in stock. If there was a LMS, within a 60 mile round trip, I probably would have bought some lighter ones, the size that PM has specified.

What I have neglected to photo are the shear webs, it will have been on the basis of being boring. I probably stuck to whatever PM specified. These are important, doing quite a bit of structural work. To be very boring the parallel axis theorem indicates they are very beneficial.

15/09/2019 15:53:13

Having spliced the sheets together I have sheeted the whole wing. I could say because the full size is fully ply sheeted. It is mainly down to scuff resistance (by clumsy me), easier to film cover and finally a stiffer wing (although on such a low aspect ration wing is hardly an issue).




Again slightly different to how PM builds, although I guess we all have our favorite ways.


Just need a body now and a few other things, hmm, it is getting there.

Thread: Thinking aloud about Spits...
15/09/2019 15:41:12

The link that Patmac found, sheds a lot of light on the development of the Spitfire, particularly the wing, and also draws some useful comparisons with other aircraft.

The virtues of elliptical wings is not at the low end of the speed range, particularly at the stall. Although many of the gliders in the 30s incorporated the plan form. I understand, again with washout, although not certain, having thrown out the magazines that dealt with them.

From the Patmac paper the NPL wind tunnel was producing erronasiously results, particularly with regard, T/C ratios and effects of camber. Apparently Mitchell and his team did not believe the data, and choose to ignore it, whereas Hawkers did believe the data and built a thicker wing.

The whole paper is full of nuggets of information with respect both the Spitfire and some other aircraft. Much is down to detail. The attention to detail in the design and manufacture resulted in an expensive aircraft to produce. Whereas the 109 right from the start, featured compromises designed to contain costs, apparently fixes to improve performance were kept in the back pocket, to be able to pull a rabbit out of a hat, when needed.

The issue of turning circle is dealt with with respect the 109, which comes down to wing loading. As observed by another pilot, if turning circle that is all that matters, then the CR 32 would take a Spitfire every time.

We need to bare in mind that the flight evaluations were undertaken primarily to obtain data. The data was used both to evolve tactics with the current opposing aircraft and feed information into the aircraft industry. From a pilots perspective, knowing for instance, that initially that trying to follow another aircraft into a dive may not be productive, if it is known your aircraft will be slower, even that in theory eventually you would catch up with it. The reason being that the opposing aircraft in most cases has done something else, before the catch. The other issue that the reports are a snap shot on a time line, which probably used more to inform pilots of what not to do, with the hope that the adversary does not know his own aircrafts weak points.

The plan form is quite interesting that the use of elliptical plan forms is pretty much avoided these days. Even Heinkel a prolific elliptical wing builder compromised to aid production with the 100, becoming a pseudo elliptical form, being a double type taper, which produced possibly a generally better aircraft than the 109. More often these days straight taper is used, again for a variety of reasons. There is the odd glider with 1/4 ellipse type wing tip, although most go for pseudo form (probably ease of production).

In some ways I am surprised that many WW2 aircraft such as the Mustang and FW 190 (variants) had radiator and carb inlets set outside of the boundary layer, yet many early side inlet jets did not incorporate splitter plates, some even took air in from the boundary layer (with poor results).

At the end of the day the Spit was an exceptional design, where the truth may not be glamorous as the PR but every bit as interesting.

14/09/2019 15:12:25

Oh! Leccy, of course they are all Spitfires.

If it was just an semi-elliptical wing a He112 and the He70 would be a Spitfire.

If the Merlin made the Spit , then a Bf (Me) 109A would not be a 109 after the first model.

They are all attractive, particularly the latter marks to me eyes, far better balance of proportions for a flying model.

We just have to accept that semi-elliptical wing is not good at the stall, although excellent in other ways. Washout is the way to reach perfection.

Edited By Erfolg on 14/09/2019 15:37:13

14/09/2019 10:35:56

On reflection, I can see that saying that the camber is reversed is at least misleading and in most cases wrong.

With the ailerons reflexed I was trying to say that is what we have done. The camber line has now changed to now be a reflexed form as used with many flying wings. If the tip were symmetrical then the camber line would be reversed, which almost certainly would be a bad idea.

The trouble with this sort of discussion, is that they are hedged with restricting caveats, which means that a concept is not applicable in some cases. A classic case of this is the general bending formula (the M/I =f/y=E/R one), there are a number of criteria that are assumed, one being that the materials properties are identical in compression as in tension. On that basis concrete is not suitable for analysis/calculation with the relationship.

I think I need to remind myself what we are trying to achieve. The first is that the root section of the wing stalls before the tip. Often we are trying to amend the AoA where the max CL occurs. We often see increased drag as useful in slowing the model down. It is often this increase in drag which requires a power on approach, to avoid slowing to much (then stalling).

On that basis the simple solution of wash out, with flaps works rather well.

Now that there are wing profile plotting/printing software like Profi, the aerodynamic solution is quite viable. No more tedious interpolating from one section to another. The down side is you need to study the data to make sure that the tip section stalls at a higher AoA than the root section, by a descent margin.

Another issue that I have to remind myself is that many of the profiles and data sets are produced for full size sections operating a much higher Re numbers. That is why i have favoured many of the Eppler profiles as many are at Re values for model aircraft. On that basis nasty surprises are avoided and consistent results are obtained.

A practical problem I have, is that I am not that accurate a builder. Foam cut or moulded wing types are normally very accurate.

Edited By Erfolg on 14/09/2019 10:44:05

13/09/2019 22:28:04

Patmac, I am not suggesting that the Aoa is changed, it is that the stall occurs at a lower AoA, in the reflexed set up, a higher AoA (due to the camber being reversed to the normal set up).

I guess we will not agree. What matters some have tried the reflexed aileron approach and have found it has worked for them. I guess others will say it made no difference. I have not heard that any suggest that it has matters worse, with respect to stall behavior. Looked at another way, crow braking is an extreme way of altering the camber of the wing. Both increasing drag and maintaining control at what is now near the stall region.

Non of it is worth dying in a ditch oversmiley

The link is a good find by you, just showing how many people are involved in design. from Pranl and Von Karman and others, whose papers were used etc and the members of the team and so on. It is rarely one man, often a collection of experiences and knowledge, some of which is used, some ignored or just discarded.

Edited By Erfolg on 13/09/2019 22:29:34

Edited By Erfolg on 13/09/2019 22:34:16

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