Jump to content
Sign in to follow this  
Rob Thomson

Tip stall prevension..

Recommended Posts

Rob Thomson

Hi All

 

Looking for a bit of input to help solve an issue with tip stalling.

Essentially I have an MH32 aerofoil & wing that is slightly prone to tip stalling.  washout has helped - but not making enough difference.

Current thoughts are that I could change the aerofoil shape as it reaches the tip.

So possibly.. MH32 at root changing to a RG15 or similar at the tip.

Would this be effective?

I am not a great theoretical aerodynamic chap so any guidance would be useful!

Rob

Share this post


Link to post
Share on other sites
czorzella

Rob, Hi

Can you give us some more details about your model, like wingspan, wing root chord, fuselage length, etc.... Please add some photos too...

Carlos

 

Share this post


Link to post
Share on other sites
Omega

How far out do the ailerons go ?

do they go to the tip ?

also are you just flying the model too slow ?

Share this post


Link to post
Share on other sites
isoaritfirst

May be worth experimenting with cg and incidence and throws before you go back to the drawing board. 

My Solius seemed prone to tip stalling the first few times I flew it. Great now. Not sure what I changed that changed it. 

Share this post


Link to post
Share on other sites
Jef Ott

Use more aileron differential?

 

Share this post


Link to post
Share on other sites
wookman

Fly faster. :D

Share this post


Link to post
Share on other sites
Jef Ott

Does the model have a vee tail?

If so, reduce CAR.

 

Share this post


Link to post
Share on other sites
Maria Freeman

turbulator strips or more induced wash-out.....

Share this post


Link to post
Share on other sites
pete beadle

Hi Rob

"I have an MH32 aerofoil & wing that is slightly prone to tip stalling"

Sounds to me like a case of the need for some fine tuning rather than changing the specification of the wing

Your use of "slightly" is the clue for me......most stalling of this type experienced by flyers is usually a flying technique problem, especially with relative beginners to flying......now, you are most definitely NOT a beginner, and I think what you are experiencing and describing here, is not a problem that will be solved without LOTS of trying to provoke the stall you are currently experiencing, and replicating the conditions prevalent when this stall occurs......

I think this is a job for a slow and comprehensive comparison of all the factors that can be changed - one at a time - and that can be cured by changing your flying technique to see, not just what cures the average stall, but what reduces or even cures the specific type you are experiencing

One quick example - an ISA flyer came to the "oldies but goodies" who do the instructing  there, and basically said he thought he'd been wrong to have bought the particular plane he'd bought to learn to fly on, "because he'd done everything he had been asked to do, but still kept experiencing tip-stalls that he was sure were NOT being provoked by him". Some of us watching his flying, already had a pretty good idea about how and why this was happening, and had suggested he takes out all the mixes he was using, reduced all the throws and only flew with an instructor for a while to see if we could sort it........we did it on the first supervised flight, where an instructor stood with him and watched him launch......the "flick" happened as he was about 50 - 60 feet out from the hill, and it was a classic case of just a bit too much up elevator, too soon, and so we replicated this with an instructor flying his plane and the flyer standing 30-odd feet along the flight line, where he could be shown that the climb-out he was continually doing was actually too steep and where the flick only occurred once his plane went through the compression on the slope and, once through it and no longer benefitting from the lift, promptly flicked......launching later with a much reduced up input cured the problem and, more importantly, proved it to him

Now, I'm not suggesting that Rob's problem is anywhere near as simple as this, but I believe that, once he'd identified what the probable identifiable cause was, THEN he could go on to stage two and start to modify the model:yes:

Best of luck Rob

Pete

BARCS1702

Share this post


Link to post
Share on other sites
Bear

MH 32 is normally considered a pretty benign section, an RG15 is going to be more prone to tip stalling than an MH32.  How accurate is the section particulary at the leading edge?

Share this post


Link to post
Share on other sites
Rob Thomson

Hi Guys 

Thanks for all the responses.

One of the reasons I have not yet responded is because I have not been the person flying the model.  It is one of my own designs - but at present I have not managed to fly it myself!  

My feeling is that the issue is most likely caused by a combination of factors:

- the model has a marginally high wing loading and needs to be flown fast.  but it looks a bit like a model you would fly slow!

- possibly the cog needs tweaking and is being flown too rear wood.

- possibly too much aileron/differential being out of wack is an issue.

I am going to suggest that the pilot tries these first - then we can move forward :-)

 

Rob

  • Like 1

Share this post


Link to post
Share on other sites
simon_t

If it is wing dropping due to wrong differential, then you would need to ADD differential not decrease it, i.e. You want the down-going aileron to go down less.  If the model is just digging a wing in when turning, then it is probably not tip stalls, and it may mean too much differential, but its pretty rare to see that in a model.

As Czorzella said though, to make any worthwhile diagnosis rather than random guesses you need to post some details and pictures.  The MH32 is a good section, I have flown quite a few models with it any never found them tip stally (and at least one had ailerons that went right to the tip, and negligible washout)

Simon

Share this post


Link to post
Share on other sites
SilentPilot

Is it definitely a tip stall?

An excessively nose heavy plane can drop the nose quite markedly when banked...

Share this post


Link to post
Share on other sites
Phil.Taylor

just tell the pilot to fly it a little bit faster !

flying too close to stall speed then turning is a recipe for a "tip stall" aka spin entry

Phil.

Share this post


Link to post
Share on other sites
SilentPilot

Yeah, that's the proper term, a spin... no idea why modellers don't use it!

You can't (well I can't anyway!) beat the feeling of being in a full blooded spin :) 2.5 turns usually does me before I have to scramble back to a thermal!!!

Share this post


Link to post
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.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  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.

Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.