Jump to content

Forum members' new models: Let's see them.


Recommended Posts

Very nice indeed Tim!

 

Re climbing under power, that is completely normal after a few seconds of increased revs from a baseline of S&L flight at around half throttle, and I wouldn't do anything to alter that with any fancy mixes, else you'll acquire confusing flying habits which won't translate to other normal models.

 

But if it climbs immediately you blip the throttle open, then it is definitely due to insufficient down-thrust. What does the plan state and what do you actually have have?  Can you measure it accurately?

 

In the free fight world short-nosed models (e.g. WW1 types with rotary engines like the Camel, Eindekker, etc) need an awful lot more down- and also right-thrust than more conventional designs with longer noses.

 

While you're about it you might also look at its right-thrust. Some pull to the left is okay when opening up power (e.g. at the start of the take-off run) but if that is really excessive then add some (more?) right-thrust. (Some would say just learn to use rudder, which I agree with, but if your model isn't nicely mechanically set up in the first place, then it'll retard your skills and enjoyment.)

 

The test for this is to fly S&L (wings must be level) into wind then increase throttle to say 2/3 power then pull smoothly to verical climb.  As the model slows (due to gravity not throttle which you keep at 2/3 power) if it yaws to the left this indicates that it needs a bit more right thrust.

 

PS: 2/3 power is just a suggestion, try 3/4 and full throttle as well and repeat tests (both down- and right-thrust ones) until you're sure there's a noticeable consistent deviation. Then, if you do alter thrust lines, run your tests in the air again and observe the difference.

 

Edited by Jonathan M
Link to comment
Share on other sites

Thanks for your reply, Jonathan. 

 

The climbing isn't dramatic,  but it's definitely noticeable when compared to the the other models that I fly regularly (Easy Street and Yeti are my current favourites and in the nicer weather I'd tend to fly an XR61 quite a bit -  they are ARTF, so I imagine things like thrust angles are all sorted by the manufacturer).

On the advice of a much more experienced club mate I have trimmed it for level flight on about half throttle - which is where the Magnatiila feels happiest as it's not a model to be hooning around with.

 

I have no thrust angles built in - I just mounted the motor square on to the firewall/F1 (is that what it's called ?) - the X mount is 12 - 6 , 3 - 9 ie + as opposed to x, if that makes sense. I've just checked the drawings and instruction manual and I cannot see that there is any recommended thrust angle - but as the model is intended to have IC I didn't really check when I built the model if I'm honest, I was more concerned with the prop clearing the cowl and the dummy engine placement within the cowl and the various spacer lengths required to achieve this.

 

It does pull to the left a bit on takeoff, but that's easily corrected with rudder and doesn't feel 'weird' to me as I'm used to using the rudder to keep models straight on takeoff. It's the climbing under power which felt a bit strange as I'm not used to it I suppose , plus the model is doing something that I haven't asked it too (although I know I have by increasing power, as a relative newbie I tend to associate climb with elevator input).

 

I will take your advice regarding the mix and I may try placing a washer under the top mounting point and see what it does - or I might just leave it alone and learn to live with it. 

Thanks for the tip on checking for right thrust - I will definitely give that a go.

 

thanks again for your reply and advice - all very welcome 🙂

  • Like 1
Link to comment
Share on other sites

Other aspects of this model which will effect climb etc, and which may well be quite different from your other models, are it's wing section, incidence angle of wing, etc.  But also check your CG:  if the model is nose-heavy you might then have a bit of up elevator trim dialled in to maintain S&L at half throttle; give it more beans and your up-elev will be quickly pushing the tail down, and so she'll immediately start climbing at a quicker rate than if your elevator was neutral.

Link to comment
Share on other sites

Without wishing to hijack this thread, I would observe that:

-  there is a range of CG position for every aircraft and the position marked on the plan may not be the optimum.  Adjusting CG position by small amounts will allow you to find the optimum position.

 

-  adjusting up/down thrust, as well as side thrust to make the aircraft less sensitive to throttle, as pointed out by Jonathan, will also make the aircraft more pleasant to fly.

 

-  mixing throttle to elevator, or rudder for that matter, doesn't always work better than making physical adjustments as above but is certainly quicker and easier to do.

Link to comment
Share on other sites

there is a range of CG position for every aircraft and the position marked on the plan may not be the optimum.  Adjusting CG position by small amounts will allow you to find the optimum position.........

 

Thanks for your reply, Peter and I hope this isn't a daft question - but how will I know whether the CoG is at the optimum position? I've seen obviously tail heavy aircraft flying and I guess I must have seen nose heavy, although to my inexperienced eyes they are less easy to spot. What should I be looking for - or am I best to enlist the help of more experienced club mates on this?

 

Adjusting the thrust angle of the motor is relatively easy as access to the mounts is pretty straightforward and I can put a washer in place without too much trouble. To be honest, I'd find that easier than trying to sort a mix as I've never done that before.

 

thanks again for your advice/help.

Link to comment
Share on other sites

10 hours ago, Tim Eastgate said:

t

 

Thanks for your reply, Peter and I hope this isn't a daft question - but how will I know whether the CoG is at the optimum position? I've seen obviously tail heavy aircraft flying and I guess I must have seen nose heavy, although to my inexperienced eyes they are less easy to spot. What should I be looking for - or am I best to enlist the help of more experienced club mates on this?

thanks again for your advice/help.

I like my CG at 25% chord.  I want a model that is not at all twitchy on the controls and flies in a rock steady flight but which responds instantly to the controls.  I have all incidences set at 0 degrees.  That means that the datum line on the airfoil section runs from the centre of curvature of the leading edge to the point of the trailing edge. and is parallel to the thrust line.The tailplane is set at the same angle.

 

I have my controls set with low rates which varies with the model and are given on the data panel in the magazine and high rates for going wild with aerobatics

All I can say is that it works for me and most people find that my models fly well.

 

There was one person who complained that one with very twitchy and he found it horrible but he also said that once he moved the CG to  where I had shown it on the plan the model was perfect....Funny that!!!

  • Like 1
Link to comment
Share on other sites

10 hours ago, Peter Miller said:

I like my CG at 25% chord.  I want a model that is not at all twitchy on the controls and flies in a rock steady flight but which responds instantly to the controls.  I have all incidences set at 0 degrees.  That means that the datum line on the airfoil section runs from the centre of curvature of the leading edge to the point of the trailing edge. and is parallel to the thrust line.The tailplane is set at the same angle.

 

I have my controls set with low rates which varies with the model and are given on the data panel in the magazine and high rates for going wild with aerobatics

All I can say is that it works for me and most people find that my models fly well.

 

There was one person who complained that one with very twitchy and he found it horrible but he also said that once he moved the CG to  where I had shown it on the plan the model was perfect....Funny that!!!

For aerobatic flying or "3D flying" one might need the CG fairly far back, although there are other criteria for optimising the CG position (such as the behaviour in vertical downlines and inverted flight). With an i.c. model one can get a feel for the twitchiness of the plane as the fuel tank (which is usually in front of the CG) empties, and then decide how much twitchiness can be tolerated. If the plane starts getting too twitchy, one needs to land pretty soon, because it gets worse each time one goes around for another landing attempt!  

Link to comment
Share on other sites

Sorry to interrupt the C of G discussion, but I have a new model!

 

This is my second own-design scale model. It's certainly not super scale, but (hopefully) a practical model that looks rather like the intended subject. And that subject is...

 

Kaproni-Bulgarski KB-11 'Fazan'. Continuing my quest for unusual subjects that are rarely modelled (and therefore no-one knows enough to pull me up on scale detail!), this is a WW2 aircraft operated by the Bulgarian and Yugoslavian airforces. It originally saw light as a shoulder wing aircraft, but was deemed unstable in tests. The subject I have modelled is the second version, which appeared with various glazing.

 

It's reasonably close to scale, but I got the fin outline wrong, and put the strut hard points on the wrong rib!

 

The model is 48" span and weighs 2lb 13Oz. It's powered by a 3536 1200kv motor spinning a 10x5 prop. Battery is a 2200 3S pack. It will have more than enough power, so should get 7 or 8 minutes flights, which is plenty for me. It's reasonably conventional construction with a few foamboard ribs to preserve my balsa stocks. Covering is laminating film, painted with emulsion, thinned and sprayed. Weathering is via my airbrush and unsteady hand. 3D printed vz30 guns from one of our very kind members. Now we've had 2 weeks of holiday and no flyable weather, it may be a while before maiden...

 

Something a bit different!

 

Graham

 

 

KB11 010122-1 KB11 010122-2 KB11 010122-3 KB11 010122-4 KB11 010122-5

Edited by Graham Davies 3
Upload photos
  • Like 1
Link to comment
Share on other sites

1 minute ago, Peter Miller said:

I did wonder about the pictures.  Graham can normally post them in the usual way.

I was thinking he had a new device for Christmas. The issue is the jpg extensions are missing, which is a setting in explorer.

 

The link shows how to post photos and add words between.

Link to comment
Share on other sites

1 hour ago, EarlyBird said:

I was thinking he had a new device for Christmas. The issue is the jpg extensions are missing, which is a setting in explorer.

 

The link shows how to post photos and add words between.

Thanks EarlyBird. I did wonder why they appeared as download icons but felt life was too short!

 

I'll quote my own post and re-add the images

 

Graham

13 hours ago, Graham Davies 3 said:

Sorry to interrupt the C of G discussion, but I have a new model!

 

This is my second own-design scale model. It's certainly not super scale, but (hopefully) a practical model that looks rather like the intended subject. And that subject is...

 

Kaproni-Bulgarski KB-11 'Fazan'. Continuing my quest for unusual subjects that are rarely modelled (and therefore no-one knows enough to pull me up on scale detail!), this is a WW2 aircraft operated by the Bulgarian and Yugoslavian airforces. It originally saw light as a shoulder wing aircraft, but was deemed unstable in tests. The subject I have modelled is the second version, which appeared with various glazing.

 

It's reasonably close to scale, but I got the fin outline wrong, and put the strut hard points on the wrong rib!

 

The model is 48" span and weighs 2lb 13Oz. It's powered by a 3536 1200kv motor spinning a 10x5 prop. Battery is a 2200 3S pack. It will have more than enough power, so should get 7 or 8 minutes flights, which is plenty for me. It's reasonably conventional construction with a few foamboard ribs to preserve my balsa stocks. Covering is laminating film, painted with emulsion, thinned and sprayed. Weathering is via my airbrush and unsteady hand. 3D printed vz30 guns from one of our very kind members. Now we've had 2 weeks of holiday and no flyable weather, it may be a while before maiden...

 

Something a bit different!

 

Graham

Images now correctly added!

 

 

KB11 010122-1.jpg

KB11 010122-2.jpg

KB11 010122-3.jpg

KB11 010122-4.jpg

KB11 010122-5.jpg

  • Like 11
Link to comment
Share on other sites

34 minutes ago, Eric Robson said:

That did not take long Graham, very good ,what's next month's model?

Hi Eric, Happy new Year!

 

Thank you, but it seemed to take me a lot longer than usual. A lot of workshop time was spent staring at things and working out how to solve all the little challenges. That's where the fun is for me.

 

Regarding the next project; 

  • Retro-fit some retracts to the Tempest. The dangly legs in fight are an affront...
  • Ritually burn the J-22. I've learned a lot from this project, but it flies like a poorly trimmed manhole cover. I'll strip anything useful from it. If anyone wants it, come and get it!
  • Concoct an obscure WW2 twin from the box of bits I got from Rchard's moving sale!

Graham

Link to comment
Share on other sites

  • 2 weeks later...

Unlike the Eclipson monoplane designs there's no carbon rods in the wings, the strength comes from the rigging wires. It would have been nice to have the option to brace the wings with CF because the rigging wires make it difficult to dismantle and it's big for a one-piece model.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...