Jocasta

[Sean Zerafa]

Thank you so much there Glyn! Much appreciated.

[Glyn44]

Here you go, as promised. If any thinning unclear just ask. I have not put on the beech sizes as you will probably have to buy a sheet anyway. Best of luck!

Glyn

[Sean Zerafa]

That is immensely kind of you Glyn. Thanks again!

[Glyn44]

Glad to be able help as I have had so much from the members of these forums. And as you can see, when I opened the pack 90% of the work was already done for me. Enjoy your build.

Kind regards, Glyn.

[Hannes Koekemoer]

I am finally able to continue again!

I had to stop for 2 months because of part shotages and the nearest hobby shop is 100 miles away. After our vacation (thankfully close to a hobby shop) I now have everything I need to finish my Jocasta Hopefully it will be up and flying within the next month.

[Colin Anderson]

On my third flight yesterday I made an error (I'm a beginner) and stuffed my Jicasta into the cabbages ! Result? One bent undercarriage that sheared off the front saddle clamps. Although there was no damage to the airframe whatsoever, if had to do some surgery on the nose as I now realise that I need some down and side thrust (I'd wrongly assumed that this was built in. As I've no idea how to get the required 3 degrees (?) I've placed 4 thin washers behind the top mounting and 2 behind the left. I'm hoping that this is about right. I was noticing that the plane was climbing sharply (rather than just rising) at anything more than half power and it was possible to prop hang just by putting the power on! I know that aircraft rise and sink depending on motor speed; but vertically?

Hopefully I'll be airborne again before the weekend. Although this is a different experience, flying wise, than what I learnt on (a borrowed Wot4) it's a please to fly. And, as I've found out, pretty tough and forgiving in inexperienced hands. 😊

[monty2]

Had a bad few weeks, at my age only to be expected. lost time down with a chest infection. all sorted thanks to antibiotics and steroids. So now its back to building, slowly, and then with my club friends to flying, Had one short flight last week with their help of my Eflite apprentice. went well so hope for the future.

[Colin Anderson]

Well flying my Jocasta today was very much a disaster!

After being almost uncontrollable and spinning into the ground, the repairs are going to take me a little while. The tailplane cracked completely across, so I've had to remove it completely, along with the fin, to effect a repair. The wing will require rebuilding of the right hand root; the dihedral brace having completely sheared and the root rib torn out. The fusalarge, undercarriage and motor were unscathed.

I'm completely mystified. Last week the plane flew okay, but had a tendency to climb sharply under more than half power. I put in down and side thrust to counteract this and the net result was worse! The plane was climbing even shaper!

And here's another mystery. When I got the plane home I noticed that both ailerons were pointing down in the position of flaps. Had I accidentally flipped the flap switch? To answer this I moved said switch and both ailerons moved further down. In other words, they acted as flaps! I flipped the switch back (which should have zeroed the ailerons) but, although both surfaces moved back, they didn't return to neutral. I checked the trim and sub trim, both were showing as being in the neutral position, but clearly the control surfaces were not! This has now got me wondering. Did both ailerons end up in the down position as a result of the crash? If so, it's strange that they would both be deflected down by exactly the same amount. Is it credible that both ailerons could have moved into this position in the air and, if so, how and why? The servos are new. What are the chances of both being faulty? How do you test a servo? I had to wind out the aileron clevises a considerable amount to recentre the control surfaces, which makes no sense! If, by some strange quirk, both ailerons had moved down, might this account for the plane climbing so sharply? Or perhaps I'm just clutching at straws? 😳

[Jim Newberry - Nuviation Ltd.]

Hi Colin,

That's a terrible shame about your model. The first thing I thought when reading your post was to wonder whether it might be possible you had the wrong model selected from your transmitter's memory? We've all done it and it is certainly very odd that after a number of successful flights you suddenly had such a disaster. As you pointed out, increasing the down thrust should certainly not result in the model pitching up under power. I would say it is highly unlikely that two brand new servos would fail simultaneously, having both given good service previously. Is it possible that your recent arrival into the cabbage patch could have damaged your receiver or loosened one or more of the plugs? Hope you can get to the bottom of it!

Jim.

[Colin Anderson]

Hi Jim,

Yes it's really mystifying. On takeoff the plane climbed almost vertical! Once up even a senior club member had trouble flying it.

At present I'm attempting to repair the wing, which broke at the root. However, no matter how hard I try I'm having trouble getting things right. I've put a new root rib in, but I just can't get two halves to seat properly. I know it shouldn't be that hard, as I did it previously when I built the wing the first time. I'm seriously contemplating repairing the wing flat, as it'll be so much easier to get the two wing halves to line up.

Regarding side and down thrust. Our club members are of the opinion that the Jocasta needs more. I'm not convinced. Originally I flew the Jocasta with no down or side thrust. It flew well, although it did have a tendency to climb sharply if given too much power. I've since placed 4 washers at the top mounting and two on the left mount. Could you give me advise on how you achieved your thrust lines?

[Levanter]

Just a thought Colin. I am unable to get a few of the pictures so I am sure if was your plane even. There was a picture where there seemed to be only two rubber bands. There seems to debates about banding whether to cross or not. To cover all bases I cross bands as well as parallel. This means I have four minimum. (And they are tight). When in storage hanging from the ceiling I use any old bands and keep the flight ones in a closed box and therefore they are basically new when flying.

With only two bands and even worse if they have been on a long time they may not hold the wing down securely.
Power up = more lift and more speed if you are having to trim down to keep level. Increasing he downthrust may just make the whole thing worse unless those bands are really doing their job. If the leading edge of the wing does lift this will cause all sorts of problems mostly serious. If the wing moves at the same time then I can imagine all sorts of unwelcome outcomes.

[Colin Anderson]

You are quite correct in saying that my Jocasta only had two bands in the pictures. This was solely for the pictures. I don't fly it that way! When flying I've always crossed the bands. I use eight of them. They are new and tight.

A have had a further thought, however. As stated, I originally flew this model with no side or down thrust. Other than a tendency to climb steeply on anything over half power, it flew very well. I found it quite controllable and could even manage a few simple stunts. As a beginner I was quite pleased with it. However, it did clearly need the thrust lines changing. With the down thrust I've put in the prop is quite low on the nose. Before down thrust was put in the prop wash was directly along the fusalarge. However, with down thrust the prop was is effectively directed upwards under the wing. This might be a daft question, but could this prop wash be lifting the wing and cause an excess of lift? Is there such a thing as too much down thrust? And, if so how does this effect the aerodynamics?

[Jim Newberry - Nuviation Ltd.]

A bit of background first - I settled on the down thrust for Jocasta based on what had worked with Jemima, since the two models were very similar in configuration. On the first flight with Jocasta, the elevator became disconnected and so I steered it around the circuit using ailerons and rudder for directional control and throttle for pitch. It behaved like a free flight model, climbing gently under power, descending when throttled back. I like models to have a slightly positive pitch power couple like this, but the sort of pitching that you've described is certainly not the way it should behave. The plan shows F1 set at the correct angle for the down thrust and so, if you are building from cut parts, there should be no requirement to increase the down thrust. Side thrust is described on the plan but setting it is left to the builder as I felt that attempting to show two different positions for F1 on either side of the fuselage would inevitably result in some builders getting things about face and building in left thrust by accident! The effect you would expect to see of adding too much down thrust would be a model that tends to pitch down under increased power.

Can you let me know whether you had a successful flight between the cabbage patch impact and the accident flight? Is it possible that the model sustained more damage in the first arrival than you had realised? If, for instance, the tailplane had been weakened such that it partially detached and made a small but critical change to the decalage or if a wing panel might have been twisted? It seems very odd that a model - any model - would fly pretty well for a number of flights but then a slight increase to the down thrust has it going berserk.

[Colin Anderson]

Hi Jim,

Thanks for this. In total my Jocasta made 9 successful flights before I dropped it into the cabbages. The only damage sustained on this occasion was a bent undercarriage, which also broke the front saddle clamps. Although technically any uncontrolled landing is a crash, this was a very gentle one; I'd cut the power on the approach (I know I shouldn't have) and missed the strip.

In my inexperienced hands I felt the model flew pretty well, if different to what I'd got used to (I learnt on a Wot 4). It did have a tendency to climb rapidly under power and our club instructor (who trimmed it out for me) had dialled in a visible amount of down elevator.

After repairing the undercarriage and adding (from what you've told me) additional down thrust, I neutralised all the trims - perhaps I shouldn't have! From this point on the model became unflyable; even our club instructor found it difficult. I'm coming to the conclusion that down thrust is not the problem. From my free flight days I remember that once the CG was right the model was trimmed by altering the decalage. Perhaps when I assembled the model at the field the wing might not have seated properly and thus altered the decalage? Perhaps the decalage on my model is not as it should be in the first place? I know there are special tools to check this, but I don't own one.

It's going to take me a while to repair the wing (I just can't seem to get the root ribs to mate properly). In the meantime I'm going to return the motor back to its original settings (although I'll probably leave the side thrust in). I'll also need to find a way to check the decalage. I've convinced myself that this is probably at the heart of the problem.

[Colin Anderson]

Well, after altering the decalage, by adding positive incidence to the tailplane - which I had to repair anyway - restating the down thrust and adding the equivalent of a church roof (80 grams!) to the nose, I'm happy to report that my Jocasta is now back in the air an flying very well. It now flies pretty much hands off. It still needed some down trim on the elevators as well as right rudder trim, but it no longer stands on its tail when power is applied. Now all I need to do is perfect landing it. In my hands it's still reluctant to come down to earth!

Unfortunately a hard landing cracked the undercarriage and broke the propeller. Although the undercarriage was cracked, with a borrowed propeller I was able to get a second flight. I find it better on an 11" x 8" rather than an 11" x 6" (recommended by 4 Max). I never got to make a third flight (probably just as well with a cracked U/C! ) due to a dry solder joint to the ESQ which thankfully showed up before flight!

[Mowerman]

I have fitted a3548/790kv motor with a 14x7E prop and 3s lipoI am only getting 250W.

I have tried a prop Drive 35/36 910kv with the same prop and lipo I get 300w.

I would be interested to hear what power ( i,e, watt meter readings) others are getting on their set-ups.

My finished model weighs 4lb 11oz so I think it would be very under powered on 300W.

[Glyn44]

Good day,

I'm a little behind all of you guys as today Sun May 3rd, I'm am about to start my Jocasta build, I know, I know but I'm retired so do not have the time for these things!

Anyway I have spent a couple of hours so far, reading through this build blog, making notes of hiccups and problems that have been answered etc.. Most helpful. I am now upto page 8.. I need to fill a gap in my very limited modelling knowledge that all you guys seem to know. What is the difference between a free and a build plan? Why is there a plan published that you cannot build from (scaleing/size?) & how do I know which type I'm looking at? I obviously do not want to start a build on the wrong one, as I will make enough more than enough mistakes during my build to satisfy anyone!

Thanks, Glyn.

[Former Member]

[This posting has been removed]

[Glyn44]

Hi Percy, The query arose from reading the following entry, and those around it. You can find it on page 8 of this jocasta thread.

"Hi All, it seems to me that you all have bought the kit for Jacasta, I tried the free plan, what a mess that was the supposed free plan in the magazine was the kit plan and not the build plan, I did report this to the editors but no sensible answer, so suggested that they sort out the plans properly and put the correct build plans into the magazines and leave the kit plans in the boxes.

Yours Mike."

Kit plan, build plan, free plan, I not with it. I thought a plan was a plan, which may, or may not, need scaling up, but its seems this might be my misunderstanding. I was intending to build from the plan published in the Mag, along with the build article, but think I will purchase the the expensive alternative from the plan service here.

[Colin Anderson]

I think Glyn's question is an interesting one. Yes, the free plan is fine for building from, although there were several mistakes of scale on this one. It's interesting that the Jocasta plan was selling for £12 (reduced to £6), yet you can buy the back issue (October 2014) for less! This does suggest that there must be a difference between the free plan and the one you can buy.

[Jim Newberry - Nuviation Ltd.]

Hi Folks,

I think I might be able to shed some light here. The comment that was made on page 8 of the thread about the difference between the kit plan and the build plan was rather misleading. There aren't two different plans depending on whether you have the magazine freebie or the bought and paid for version. I think the builder was expressing his frustration that some of the shortcomings of the free plan made constructing a model from it more complicated than it needed to be whereas, had the same plan been provided with a kit then the shortcomings of the plan would have been less of a problem since all the parts would have been supplied. As for the reasons why buying the plan from MHS works out more expensive than buying a back issue of the mag, well I can only imagine that this is a commercial decision made by MHS. For one thing, I understand that plans ordered online are printed to order, which must add a cost whereas I would think that back issues are supplied from a store of magazines that were left over from the original print run. Once all those issues have been sold - I would imagine - no more will be printed, at which point the pricing of the plan will no longer seem odd as it will be the only source. Either way, you will be getting the same plan, albeit on different paper if it has been ordered from MHS. Please, please, please note that all the above is supposition on my part - I don't know for certain how MHS set their prices and I may be talking nonsense! Glynn - if you have read the Jocasta thread you will have been made aware of the various glitches in the plan and, knowing about them in advance, you will have no problem building a model from it. A handful of Jocasta models have flown successfully having been built from the free plan and if you encounter any difficulties along the way please feel free to post a question on here or contact me directly and between us we'll be able to set you straight.

Jim.

[Glyn44]

Ok thanks all, I'll press on now and see what happens.

I feel for you Jim, reckon you must be a bit fed up answering all the queries that occur! I can only say it is appreciated.

Happy days, Glyn.

[Mowerman]

Hi Glyn

The full size plans included in the magazines are, from my experience, sufficient to build from.( I have built 6 or 7 from various mags including the Jocasta) If you look through various build blogs in the mass build topics there are only occasional problems encountered and a question on this forum will generally sort things out. Obviously it is wise to measure as you go.

Do bear in mind that it is always helpful to get the plan copied in order to preserve the original. Most copy shops can do this for a couple of pounds.

Good luck with the build.

[Glyn44]

Hi all,

thank you for that info. I have started on the fuselage, all ok I think,,although a couple of issues I am not sure whether it me, or the woodpack. Following optics will illustrate:

1: the lugs on the formers do not fill the side slots.

The formers are seated as far as is possible.

So is this normal, and should I fill if it is not? Also on the pic above can you see that F6a seems to be to small, again the side slots are unfiltered by the lugs and the body of F6 is not wide enough to touch either side ig positioned centrally.

I'm not sure that any of these points are to be worried over, but it takes a away my overall confidence of the woodpack for me. What will I find when it maybe too late without a lot of ungluing, dissembly etc.

Anyway plz let me know your thoughts.

Glyn.

[Jim Newberry - Nuviation Ltd.]

Hi Glynn. The lugs aren't supposed to fill the slots completely, if they did then you would have exposed end grain on the outside of the fuselage which would leave an uneven finish after sanding. There is no need to fill the resulting gap as it will be bridged by the covering. F6a just provides a seat for the wing trailing edge and so it is not important that it isn't the same width as F6 although for the sake of neatness it would be better if it was (although it is not visible once the wing is in place) .
Jim.