yak 55 32" hobby craft foamboard build - Page 3 - RC Groups
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Sep 23, 2017, 10:22 AM
flyin' fool
goldguy's Avatar
Windy?? Build a delta. They laugh at the wind. A 'true' delta that is, not a flying wing that's called a delta.

Small wires and plugs are restrictive. I seen a controlled oranges to oranges, apples to apples test comparing JST against Mini Deans. Changing over to the Deans gave almost two more minutes of flight time.

Why battery manufacturers put JST on high amp draw lipos is beyond me. I'm sure the length of the wire/plug arrangement and the maximum voltage has something to do with it.

I'm all ES3 since I'm under 20A on all my birds now. Dumped all the big stuff to stay under the new laws here in Canada. Over 250 grams/8.8 ounces and there's a long list of rules, plus you'll soon need proof of $100K CDN of insurance.
Last edited by goldguy; Sep 23, 2017 at 10:37 AM.
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Sep 23, 2017, 08:14 PM
Kimbers Keeper.
BHOFM's Avatar
Quote:
Windy?? Build a delta. They laugh at the wind.
This will fly in a Cat2 hurricane.

Sep 25, 2017, 04:59 AM
Registered User
Ok just been out in very light breeze today, its lovely.

Still trying to work out the kinks, while i can fly around i think im still having (if this is the right description) what i think is "pitch sensitive" but the CG is bang on where it should be. Should i add more downthrust???

basically when flying around and not doing 3D the wings tend to randomly rock, im wondering if thats why ive ended up crashing when doing tight turns having it suddenly flip on me./ being inexperienced though i find it difficult to actually no what went wrong or even explain exactly what happened.

Toda i nosed it intot he ground again, although that was because the prop flew off hovering 20 foot up. I will say though that it hovered very well even with my inexperience, was able to hold it straight up no rolling, the prop came off as i had judged it wrong on the elevator and the plane started tipping over into inverted so whacked on the power to give me more elevator to stop it falling over and thats when the prop flew off.

O ring i think isnt tight enough.
Sep 25, 2017, 06:03 AM
Kimbers Keeper.
BHOFM's Avatar
Use two o rings.
Sep 25, 2017, 07:08 AM
Registered User
Quote:
Originally Posted by BHOFM
Use two o rings.
yup thats what i ended up doing its fine after that.


Well i think im closer. managed 4 full batteries without crashing, even a couple evergency landings, once when i went into a hover and when i gave it full power it started vibrating (thinking the motor mount screws came loose) i backed of and came into land quick turns out it was just the prop pulling away from the prop saver under heavy load. 2nd time my battery compartment gave way and the batter was hanging off LOL managed to land it :-)

I dont think downthrust was the answer, it seems to be wanting to nose down although it is now slightly nose heavy. if i let the power of it will go into a shallow dive,. I moved the battery back which helped but it still needs a fair amount of elevator trim.

I think ive just been trying to fly it too slow and its just me hitting the stall speed of the wings after some flying around and figuring out how it was responding i was able to start doing harriers although not as slow as i like but then it is almost twice as heavy as it should be.

flight times are decent upto 10 minutes on a 3 cell 850mah battery.
Sep 25, 2017, 01:55 PM
flyin' fool
goldguy's Avatar
Pitch sensitive = tail heavy
Sep 26, 2017, 01:55 AM
Registered User
Quote:
Originally Posted by goldguy
Pitch sensitive = tail heavy
definatly not tail heavy , it turns out its actually nose heavy. a club member had a look at it, said its tail heavy until i showed him the recomended cg mark (he was measuring it from the wing spare) and was oh its nose heavy then.

Pitch sensitive is the wrong description, after getting used to how it flys and how to get it flying much slower, aswell as increasing expo to 60% its not pitch sensitive. its just wing rock. ie im reaching the stall point and it just starts the wings rocking, ofcoarse not really how this plane should fly but it is almost 400g so the wingloading isnt great but it does fly and fly fairly well once you get used to the corrections needed to calm the wing rocking.
Last edited by bazsound; Sep 26, 2017 at 03:26 AM.
Sep 26, 2017, 12:37 PM
Registered User
Shifting the weight back didnt make much difference, neither did taking it passed the recoended cg marker making it tail heavier. although it did soften the wing rocking. There was hardly any wind at all today but the wing rocking is still present and even when going faster.

Im wondering if its actually the foam flexing, ive been finding the elevator just isnt enough and brought in close to see what was happening when it was flying. control surface is flutering..

Need to repair it again as the rudder hing gave way after a crash
Sep 26, 2017, 03:22 PM
Kimbers Keeper.
BHOFM's Avatar
Just looked at the pictures again, what kind of spar did you put in the wing?
I did one with too small a spar and it flew like crap. You could see the wing
flexing. And it got worse as we tried to fix it. I pulled the electronics and built
another one with a .157 spar in the wing and a .125 spar in the horizontal.
It flies like a dream and it a bit on the heavy side and handles wind like a champ.

When the wing flexes, the ailerons don't work, they are curved with the wing.

Some times you have to build several to get it right, No rocket science here.
Sep 26, 2017, 03:43 PM
Mike's Ma Maaaaaaaaan
PaulB's Avatar
Good to see you having fun (and learning).

Enjoy.........

Paul
Sep 26, 2017, 04:27 PM
Registered User
Quote:
Originally Posted by BHOFM
Just looked at the pictures again, what kind of spar did you put in the wing?
I did one with too small a spar and it flew like crap. You could see the wing
flexing. And it got worse as we tried to fix it. I pulled the electronics and built
another one with a .157 spar in the wing and a .125 spar in the horizontal.
It flies like a dream and it a bit on the heavy side and handles wind like a champ.

When the wing flexes, the ailerons don't work, they are curved with the wing.

Some times you have to build several to get it right, No rocket science here.
i think you may have hit the nail on the head. i have been watching it fly when i come round doing slow low circles and spotted the elevator flapping. One side is stiffer than the other (due to the control rod) so that itself could be making it randomly rock as one side of the elevator will twist under load.

I used a 2mm spar on both the wings and elevator, the tail had the paper removed to reduce tail weight which in turn made those parts more flexible.


i wouldnt say it flies like crap, keeps you on your toes lol.

I think that will be the plan is to build another one, wonder if its maybe worth pulling the paper off and using coloured tape (which will reduce the weight slightly while helping keep it stiff) and put larger spars in the wings, i just checked your spars and mine are smaller.

This ones quite worn out too aswell, crumples at the joins so the fuselage isnt as stiff as it was.
Sep 26, 2017, 05:54 PM
Kimbers Keeper.
BHOFM's Avatar
Build another one with a good spar. .157 minu. Put it near the CoG, where all the stress is, a bit
smaller for the tail. LEAVE the paper on. Use hot glue sparingly. Just enough.

My 33" Laser weighs 390g ready to fly with a 3s 1000.

You need to find some Readifoam. Most craft foam is way too heavy.

On the bottom view you can barely see the spar, I put white tape over it.

This thing is a dream to fly. Some top 3D pilots have flown it and rave about it.

The motor is a 1100kv from Banggood, $5, 20a esc, 9X4.7 GWS, or APC prop. About
140W.

The design is stolen, so I can't post plans.



Last edited by BHOFM; Sep 26, 2017 at 06:02 PM.
Sep 26, 2017, 06:10 PM
Kimbers Keeper.
BHOFM's Avatar
BTW, the original version of this plane had a .080 spar, 2mm. and all the problems you are having.
The first few flights were great, then, it just got worse and worse. The wings were bowing up
several inches when you pulled up hard. There were wrinkles everywhere.


Here is a link to the original plane, I have two, but they are not good outdoor fliers. My copy is
over twice the weight and flies in any kind of wing.

http://www3.towerhobbies.com/cgi-bin...XFFMH&P=3#tech
Last edited by BHOFM; Sep 26, 2017 at 06:18 PM.
Sep 27, 2017, 02:39 AM
Registered User
Quote:
Originally Posted by BHOFM
BTW, the original version of this plane had a .080 spar, 2mm. and all the problems you are having.
The first few flights were great, then, it just got worse and worse. The wings were bowing up
several inches when you pulled up hard. There were wrinkles everywhere.


Here is a link to the original plane, I have two, but they are not good outdoor fliers. My copy is
over twice the weight and flies in any kind of wing.

http://www3.towerhobbies.com/cgi-bin...XFFMH&P=3#tech
Thats probably i good plan, i have a few places that i can get a few sheets of XPS foam although it does not have paper but i can cover it with coloured tape, which will add just as much if not more strength that the paper, with advantage of being water resistance (landings on wet grass are starting to take there toll)

The wings arnt creasing, but they are probably flapping in flite, which i guess is the random twitches in roll.
Sep 27, 2017, 04:23 AM
Registered User
Extreme Sports's Avatar
I assume your 2mm spar is just a 2mm rod? If that is the case it adds nothing but weight, unless your structure is such that the combined effect of the spar and the wind is stiff - the rod on its own is not very stiff.

You'd be better off with a strip of CF bonded to the top or bottom wing surfaces (in effect creating an I beam), or using a 5mm CF rod (the rod on its own provides the stiffness).


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