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Nigel R

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Posts posted by Nigel R

    Unstable model

    in All Things Model Flying

    Posted

    Answering the OP's question...

     

    I can only agree with the suggestions to move the CG forward a bit, double check the incidence. Might be worth looking at whether there are any significant warps in the wing, too.

     

    Biplanes are always a bit draggy and sometimes have a few oddities around the edge of their performance but plain vanilla upright flight, inverted flight, with throttle high or low, and landing and whatnot, should all be fuss free and predictable. A Skybolt is essentially your "average aerobatic bipe".

     

    You definitely did the CG from the LE of the top wing, yes? (just checking)...

    Testing lateral balance on the bench?

    in All Things Model Flying

    Posted

    matches what I've done in the past... I'm sure more accurate ways exist, but this gets close enough to start with.

     

    you can also test balance in the air by repeatedly pulling up from straight and level and noting whether there is a consistent slight roll to one side; I'd back that up by checking on the bench

     

    prop driver isn't always dead on centre though, that's one caveat.

    • Like 1

    Would you reinforce this?

    in All Things Model Flying

    Posted

    1 hour ago, Witterings said:

    It's a 48" Skywing Edge hybrid, comes in at 1111g without battery which is another 209g 

     

    A 48" 3d model clocking in at 1.3kg should land about as hot as your average ice cream, I think borderline whether you'd benefit much from convert to wire gear, just epoxy what you got back in place. Add some 1/32" ply doublers inside the fuse sides (make sure they extend fore/aft of the gear by a couple of inches) and then reinforce the gear plate / doubler joint a bit with some hard balsa or liteply. Should be plenty.

     

     

    Would you reinforce this?

    in All Things Model Flying

    Posted

    On 18/06/2025 at 08:25, Witterings said:

    Managed to "take out" the undercarriage as per the photos on a new plane, it's a fairly clean break so expoxy'ing it back in would be fairly simple but would you do anything else to try and reinforce it and if so what?

    IMG_5023.jpg

    IMG_5024.jpg

     

    What's the airframe? Size? Weight?

     

    The mount plate looks a bit fragile.

     

    If I'm honest I'd replace it for a torque rod type gear.

     

    23 hours ago, Ron Gray said:

    not just touching the wheels but making sure that the model rolled along the strip for as long as possible before taking off again

     

    is the best practice for smooth landings you can do. Spend a few flights doing nothing but.

     

    Additional challenge, keep the airframe rolling on the main legs only, without the nose gear or tailwheel touching the ground.

     

    F35

    in Full Size Aviation

    Posted · Edited by Nigel R

    4 hours ago, Robert Cracknell said:

    Payneib..

    1. Typhoon - in a recent exercise in the USA Luftwaffe Typhoons defeated the F35s. Apparently the need for F35 to carry external fuel tanks negates the stealth features of the aircraft. Also Typhoons are home grown and not subject to the vagaries of the Trump administration if he chooses to turn his back on NATO

    2. Rafale - if, as suggested, our carriers are retrofitted with catapults (it was designed in at the outset but not fitted) the marine version of the Rafale would be an option.

    The UK is running a risk by having two carriers only able to launch one type of (American) fixed wing aircraft.

    The Americans are also keeping their AV8B in service for longer due to the shortcomings of the F35.

    The Americans cannot have a lot of faith in the F35 as F15, F16 and F18 continue in production and there are rumours of F22 production restarting.

     

    With respect Robert, (next to) none of that is true.

     

    Plus.

    The current F18 is totally different airframe to the original F18.

    F16 is a previous gen, export market product.

    As is F15.

     

    Any mention of air combat superiority of Rafale or Eurofighter over F35 entirely misses the point of what F35 does; if an F35 is dogfighting then things have already gone very very wrong.

     

    Nobody is making any new F22, not a chance, nada, its now old tech anyway.

     

    Yours, industry insider (of sorts).

     

    All I state above is verifiable online.

    Bigger faster and fancier (new design)

    in Own Design Project Blogs

    Posted

    I'd strongly consider Simon's suggestion. It simplifies things a lot. I don't know what the appropriate size servo will be for this build but at this kind of scale the links start being a larger percentage of the whole control loop.

     

    That said, I've used snakes for my current build which has twin fin/rudder arrangement. But... It is bigger (7 or 8lbs expected) and I have 40g standard servos on each fin. The snakes operate each rudder directly (well, there is a horn that goes forward of the hinge line - that will allow me to hide the whole linkage in the tailplane).

     

    I like the Comet shape the best! Very racey.

    Boomerang that won't come back

    in Building from Traditional Kits and Plans

    Posted

    I'd make ribs for this sort of wing from the foamboard that hobbycraft sell - it costs buttons by comparison to balsa ribs. That said your existing material choices look perfectly sound.

     

    Space the ribs around 3" or maybe a touch less. What works to get 11 or 12 ribs on a wing this kind of size (with 10 or 11 "gaps").

     

    Are you using bands to hold the wing on, or dowels and bolts?  If it is bands - add an extra rib in between the two root end ribs. It'll help keep the sheeting in one piece.

    Eneloop performance?

    in Gadgets and Electronics

    Posted

    15 hours ago, Martin Harris - Moderator said:

    Popular wisdom is that in order to reduce peak detection errors, you should charge at at least 0.5 C but it does seem that trickle charging at 0.1C may eventually cause damage.  NiCd cells were so much easier to manage...

     

    Trickle charge can be bad if they're left in 24/7, but that's not the kind of case we're talking about here.

     

    I maintain that NiMh are very easy to manage.

     

    1 hour ago, Jonathan M said:

    NB: I've never seen 2000mAh out of a 2000mAh pack, always only 1800mAh.

     

    1800mA on the charge part of this cycle at 1C is a pack in excellent condition. And, note, that result from a 10 year old pack. Speaks volumes for quality.

     

    On a similar note. I inherited a small pile of eneloop flight packs of somewhat indeterminate age (most likely all around 2010 - 2015 purchase date). All 2000mA AA cells. To see what I had, I cycled them twice, 1C discharge, 1C charge. Not a single pack was below 1700mA on the charge cycle. The Vapex low discharge cells I bought did not age nearly as well - several failed cells, a fair amount of lost capacity. If I remember I'll post the results. Pretty impressive given they'd just been chucked in a box for 10 years and not touched.

     

    1 hour ago, Jonathan M said:

    it appears that what the pack needed was a full in-out-in workout!

     

    I forget which electrode suffers most in NiMh but (IIRC) tiny crystals form on the electrode and block it from contacting the electrolyte. Some of these are broken down by a decent cycle. Formation is faster at full discharge and slower at higher charge levels. I think. I'm a bit hazy on the details here (sorry). Regularly used packs won't suffer too much though.

     

    As ever YMMV.

    • Like 2

    Eneloop performance?

    in Gadgets and Electronics

    Posted · Edited by Nigel R

    Mine uses 4mV as default, I believe.

     

    The lower the better for NiMh (the ideal point is where the voltage curve is flat, but detecting that point is beyond most hobby chargers). Too low and you would get false peak detection problems. I would stress 7mV isn't "too high" to cause any concern though.

     

    37 minutes ago, Jonathan M said:

    I don't slow-charge using a wart,

     

    Main benefit of slow charging nimh packs is that it will balance the cells.

    Eneloop performance?

    in Gadgets and Electronics

    Posted

    10 hours ago, Jonathan M said:

    On the discharge I set cut-off to 1.0v per cell, and on the charge I set delta-peak to 7mV.

     

    With NiMh, the lower peak the better (within the limits of your charger, some aren't accurate enough). They show a flatter peak than NiCd do. IIRC 7mV is getting toward a NiCd setting. Not exactly a deal breaker though.

    • Like 1

    Selecting Electric Retracts

    in Building from Traditional Kits and Plans

    Posted

    That's the rub Bruce, the torque rod setup is somewhat more straightforward to key into the main wing structure (especially in a foam wing). The underside block is mainly pushed upward into the wing, and backward; both of which it can easily resist in an average wing structure. The top block - holding the torque arm - is pushed forward; again, easily restrained by your average surrounding wing structure.

     

    With retracts, if you can attach the mount plate securely to a couple of ply false ribs, then you have a similar structure in place - this will also distribute load to the upper and lower sides of the wing structure.

     

    Coil springs on piano wire retract legs help absorb the loads. If I'm making my own legs I wind several coils on, rather than using a straight leg or a single coil. All grist for the mill. Sprung oleos are clear winners in terms of properly absorbing the bumps and bounces. All of which takes a bit of stress and strain away from the mounting points.

     

    Unless your landings are the butteriest (?) of butter smooth and you fly from the perfect tarmac strip, the legs themselves will often need a tweak. C'est la vie.

    Selecting Electric Retracts

    in Building from Traditional Kits and Plans

    Posted

    In my (slightly) limited experience of retracts: Solid install of any mount plate or bearers is key to long life. Get them keyed into the wing structure and spread the load, just like any regular U/C.

     

    That's it really. "With a long enough lever" etc. Get the retract on a nice solid mount and make sure it's firmly attached. Easier on a built up wing - foam wings (in my opinion) need extra structure embedded to achieve a decent mount for the retract unit.

     

    I would note, the average retract unit has about an inch gap between fore and aft fixing points. This is not so dissimilar to the length of "arm" on a torque rod setup. Nearly every fixed gear sport model I've built has that kind of U/C. To my mind this means the retract unit is putting a similar strain onto the wing structure as a fixed U/C would - so it's not impossible to handle. Fuselage mounted aluminium or carbon gears are similar - often quite narrow where they attach. These also need solid structure to bolt to.

     

    YMMV.

    Eneloop performance?

    in Gadgets and Electronics

    Posted

    1 hour ago, Martin Harris - Moderator said:

    My limited understanding is that they are physically/chemically different from “standard” NiMH cells, resulting in low self discharge but with a higher internal resistance resulting in lower performance at higher discharge rates. 
     

    it’s a design characteristic rather than a quality issue. 

     

    To the best of my knowledge, they don't have higher internal resistance than standard NiMh cells. Eneloop performance under high load is very good - as good or better than any other NiMh, I would think.


    Vapex are pretty good for the money, but - personal experience only - I have had several cells fail. I use these for household use, torches, remotes, bike lights etc. Not sure I'd use them for an airframe any more.

     

    YMMV of course.

    Selecting Electric Retracts

    in Building from Traditional Kits and Plans

    Posted

    22 hours ago, GrumpyGnome said:

    I don't use a retract servo, just a decent 'normal' one...

     

    retract servos run 180 deg for good reason, this puts zero load on the servo when locked either up or down; it also means the servo produces a lot more force at the extreme of travel, which all aids getting the lock in place; a normal servo does not.

     

    To put it another way, the geometry works for the retract servo and works against a normal servo.

     

    Of course you can modify some normal servos to travel 180 degrees, but far simpler and better to buy one designed for the job.

     

     

    Whilst a well adjusted mechanical retract is very reliable, it is well worth checking the operation before every flight. Legs can bend and foul the wheel wells. Find out before committing aviation.

     

     

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