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Feefo

I'm after advice on getting an old Needle 124 prototype back in the air. 1st problem is the ballast tube has a piece missing in the wing joiner area which I think is causing the ballast to get stuck. I can't see any obvious obstruction, and with a little bit of sanding with a stick that had sandpaper glued to it and a good amount of polish applied with cotton buds on a stick I managed to get them out. Due to the ballast tube being rectangular I'm not sure of a possible way to fix, access is restricted and I don't know if I can get in there anyway and do a decent job. A possible solution is to drill each ballast piece and run some string or wire though to be able to pull them out. I'd also thought about using a single bar but I'm not sure there will be enough clearance over the servo's, which is something else that needs sorting. I think I could probably use the plane without using the fuse ballast, but I have it and it would be nice to have the option to use even though it's not a huge amount. It does have the steel joiner but no extra ballast for the wing, TBH I have never had a plane feel so heavy and considering my return to the slopes I'm not rushing out to load it up to it's max anyway. 

Another thing it needs is servo's for the V tail, space is tight and it looks like I need the servo output shaft about 28mm from the base, otherwise it's forcing one of the pushrods to bend which will cause binding. Options look limited, KST08 plus would fit and possibly the KST DS145MG, the wing servo's are all S3150's on LV, so do I stick to LV servo's on the V tail or go HV and look to regulate the voltage to the wing servo's? I don't really want to refit new HV servo's all around. Other option could be to fit new longer pushrods and move the servo's forward as it needs something fitting to the nose to stiffen it up a bit IMO. 

Any advice appreciated.

 

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wookman

More vintage plastic! Wonderful. 

Mks 6100 are worth a look. Very small. Got them in the Radical. 

If you put the servos well forward and the rx behind them you may generate enough clearance to get a single stick of ballast in and out which will obviate the issue with the damaged ballast tube. 

Ballast could then be a solid bar of aluminium for light days and steel for heavier days. If you need more you will have to cast some lead into a tube carefully or bite the financial bullet and buy some tungsten. 

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Feefo

Cheers, I'd overlooked the MKS6100, it does look like a good option. Do you use 6100's all around Wookman? I have 5 in a small hotliner and find them a bit thirsty, but I only use a small 500mah 2s lipo for the receiver/servo's. 

Returning to the slopes is really for the days when it's windier than I like for my electric models, so I'm not sure how often I'll be flying when conditions are light but would prefer to have the carbon joiner available rather than only having the steel one if I fly on lighter days. Casting lead for ballast is relatively easy, getting some brass bar for the wings is a possibility too but I don't think I'll splash out on tungsten. I'm trying to keep this a 'cheap return to the slopes' plan, if all goes well I'll look at getting a newer 2nd hand model, but for now the plan is to just get out and fly and get back in to it. If it goes to plan I might considering doing some F3F races but I need to walk before I run so 1 thing at a time.

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Phil.Taylor

MKS DS6188 - for the fus - used them in a couple of planes now. Small & fast.

Phil.

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Feefo
38 minutes ago, Phil.Taylor said:

MKS DS6188 - for the fus - used them in a couple of planes now. Small & fast.

Phil.

Cheers Phil.

They're lower torque than the 6100's, but I'm not sure how much torque is actually needed out of a servo, especially elevator servo's and whether the AUW  comes into the equation. 

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wookman

Hi Feefo. Mks 6188 in the fuz on the Radical not 6100. They work well. Got the Radical from Phil! 3150 in the wing so it all runs off 4.8 volt nihm. Old skool. The 6188 is small quick and plenty grunty enough for v tails. 

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satinet

Ds6188 is somewhat taller. 

The mks 6100 and the bluebird equivalents are very small servos. 

As suggested above you might just want to use solid bar rather than slugs. 

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Feefo
1 hour ago, wookman said:

Hi Feefo. Mks 6188 in the fuz on the Radical not 6100. They work well. Got the Radical from Phil! 3150 in the wing so it all runs off 4.8 volt nihm. Old skool. The 6188 is small quick and plenty grunty enough for v tails. 

Good to know they're strong enough but went with the 6100's. I had an old Savox servo which the output shaft matched the height of the MKS 6100 (actually had a 6100HV but I'd arranged a return on it and didn't want to open it to check fit). Once they're fitted I'll look at the ballast options, but the nose is really tight as this was the prototype and there's not much room to move them forward. I think I'll fit in the old locations then check how balance is going, I need to consider I might need to add lead to the nose to balance especially if I end up getting the wing ballast and I could easily mess that up if I move things too much. Looking at battery options it'll need a 2+2 AA pack which will need to stand up but I think I'm abandoning the idea of adding any former.

 

 

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  • 2 weeks later...
Feefo

UPDATE

I looked at the ballast tube but couldn't see what was stopping the ballast sliding freely. In the end I took some 10mm square wood and glued some sandpaper to it which I used to clean up the inside of the ballast tube. I could feel something as I applied pressure but had to take my time to not overdo it and sand the tube unnecessarily. 2 pieces of ballast would then slide in and out easily but the others still wouldn't go past a certain spot. In the end I lightly sanded each piece of ballast and chamfered the ends which has worked and now they slide in and out no problem. I can't see how to fix the broken tube without risking getting glue inside and needing to repeat the above.

V tails were reset as they didn't seat properly, possibly because they're not the originals which is why I think the pushrods were too long. Rods were easy to fix, used an M2 die to thread more of the rod then trimmed a bit off and put on MPX clevis , servo's and battery fitted.

Balanced at 97mm , 3588g with the steel joiner, ordered some brass flat for ballast for the wings which needed a few minutes on the bench grinder to get them all the size. Worked out roughly how much weight needs adding or removing from the nose depending on ballast options, fully loaded it is just under 4.5kg.

Plans to go the Mynd today were aborted after finding a nail in my tyre, went to the garage and got it sorted and decided to go to the LMMGA site 'The Gate' instead. Ended up siting in the car until the low cloud and showers moved on but after a flight with the Sunbird and Typhoon I decided to throw the Needle off. Conditions weren't great, it had been a bit over 15mph while flying the others but it seemed to drop off as I readied the Needle. Undeterred and recalling posts saying it likes carrying ballast and is happy doing so in less than ideal conditions I decided it was being thrown off. And off it went....slowly dropping below the horizon as it moved out. A few seconds later (seemed longer when I was watching it heading down the hill) it picked up speed and I was comfortable to give a little up and we were in business and cruising around. It needed a fair bit of up trim, I think I'll move CoG back a bit and I think it needs more snapflap, maybe a touch more elevator as well but otherwise it flew pretty good, good enough I spent nearly an hour flying it around! Landing was easy and thankfully I avoided all the sheep droppings. 

Can't wait to fly it again 

Dave

 

 

 

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wookman

Look forward to seeing it out on the course. 

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Feefo

I need more time with it but I'm game for doing a few comps

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