Nigel R

Hello and welcome I'd steer clear of sticky tape for covering, the rolls of heat shrink film are tailor made for the job. You won't need to cover an RC airframe with basswood. The structure will be strong enough without it.

I think LiFe is a single specific chemistry. The terminal voltage is different to the typical LiPo cell that we use, so they're "easy" to tell apart, I guess. LiPo is more a construction method. Can include many variations of lithium chemistry, gel makeup, polymer, and cathode material. Both degrade with heat and extreme of charge/discharge, which includes developing the gas build up / puffing problem. Slow or fast charge? Just wondering if there has been a heat build-up issue, where the pack was buried inside a model during charging; fast charge might well exacerbate that.

Looks rather battle worn at this point! Phil, I thought it was the LiFe chemistry that was "less prone" to inflating. Maybe this pack had an internal fault that caused the swelling? Although it looks like both cells have swollen.

More high tech than my answer. Just goes to show, a little practice means even a makeshift tool can get good results. My low tech answers... For flat surfaces, I poke a scalpel blade through some scrap balsa to make a centre gauge (if it doesn't mark the exact centre, I have another go). Once I've marked out the slots with the above high tech centre gauge, I use a snapped stanley blade to make the hinge slot. If that all comes out "just a tiny bit off one way", I lightly fret out one side of the slot a fraction. For this I have a snapped off piece of metal band clamp - one side of the band is smooth, and the other has some roughness where the screw slots are stamped. It works far better for me than the dubro hinging centreline widget, which seems to be marginally worse than not using one at all, except that I paid £10 for the privilege of messing up some hinge slots. The ultimate low tech, low cost, self aligning hinge... use nylon string and sew them together.

Very neat - I like this.

I think the exhaust is simply cooler on two strokes as it leaves the engine - all that unburnt fuel + fresh oil that goes straight out will keep it cooler (and slimier).

Have you tried setting fire to a NiCad, NiMh, lead acid, etc? Sure... they can fail, but tend not to turn into an incendiary device. Both factors certainly do not help. Especially with our pattern of use. Fast discharge, fast charge. Charging needs monitoring, fast charging even more so. Etc. Like most other flyers here - I've never had a problem either... (which is exactly what all the folks with burned down garages said, right up to the point the garage burned down) We would all acknowledge that storing petrol needs to be done with certain precautions (out of direct light, cool place, no open flames, etc). Lipos are no different. Happy charging everyone!

I work in aerospace. My employer's client is very much worried about the possibility of cell fires. We make probably the most tested and safe chargers going. Fire is still of concern. We get sent back to re-do things if they're not happy with the approach or implementation or testing, at great cost. A cheap charger won't swing the odds in your favour. But it is not the only cause of fire. Cells have internal chemistry that can, as noted above, light up without warning. Even stored. Although the chances are much lower than during use (or abuse). I doubt any of the chargers in our sphere of use are tested to any great degree. Even the expensive ones. Safety for these things involves never charging unattended, and storing somewhere fireproof when off charge, too. The "peak risk" is during use/abuse, either discharge or charge. And immediately after. After working with batteries for some years, I prefer IC, too. Although I still have a few smaller lipos in use I won't go to larger cells with higher stored energy and more combustible material, nothing over 3s3000 size for me.

1930s aircraft with the upright inlines and a similar snub nose would have the opening in the cowl directly in front of the cylinder head for that reason. Spartan Arrow (DH Gypsy inline) for example / inspiration: Simpler... the Avro Avian just let it all hang out: The later (?) monoplane version of the Avro Avian was slightly more streamlined:

Could the nosewheel fold forward instead? There's no engine to get in the way 🙂 What about using 3 blade props?

29 would be a good choice, I think a 25 would be a bit too little. Mine is 480W of electric instead... great flyer. I don't mind showing it off - my dad built it many years ago:

I think Don has it. They are building aids. Only there to ensure everything is level until the wing sheeting goes on. The original Aeromaster, the bigger version, is a lovely flyer. I am a confirmed fan after building one a few years ago.

Those look somewhat challenging to fix securely! In your picture, I guess the left side of the rod is fixed in place and the right side controls the main articulation in the fork on the right side?

25kg at 15g presents a total weight of 375kg. That's going to need some pretty careful structural analysis. As an option, I would consider looking at a smaller airframe, like sub 5kg AUW. Plenty of RC pylon racers exist, at that sort of size, and they experience 20g in sharp turns when racing, so the structural and aerodynamic aspects are somewhat understood empirically, if not through analysis.

Looks really good. 👍 Must admit, if I did this project again, I'd build it as per kit without worrying about mods or retracts. It's a really nice sport hack model as is. And a simple build.

That'll do it. Neat solution. 👍

Yes that is close. But. I can't recommend making that a z bend enough. It's asking to vibrate out. Sorry to sound negative again, but I would not be happy without a locking connection or some sort there. Or make a big hole in the firewall and secure the snake about an inch back? Or a different mount with longer beams? Another tactic I've used is to bring the snake in from below the carb at 45 Deg, that gives more wiggle room for hardware.

That was put down pretty damn hard. Wonder what happened to cause that? I saw a report of strong crosswind, but the descent looked smooth and controlled... apart from being way to steep.

Indeed it does Ernie. The project brief is certainly very open ended. How are you getting on so far Michael? Regarding your research suggestion, I expect you may have noticed by now that early jet aircraft and aerobatic aircraft are very different animals, with very different mission parameters, speed ranges, flight envelope, structures and payloads...

Is there a particular reason you want to run the Veco 19? (rather than, say, a more recent engine)

Looks good. Scratch built airframes are full of these minor engineering challenges - all part of the fun 🙂 Sullivan are 'new ownership' and I'm not sure they produce in much volume, hence the price increases. The Dubro Lazer rods are as good as Sullivan, I think, and about the same price as Sullivan used to be. I can't possibly take credit for the bulkhead thing!

Might be tricky on a Zagi or a. n. other flying wing or weird shape airframe. TBH I doubt that bullet point had as much time applied to it as our two posts have spent discussing it.

is excellent stuff. I only don't buy it as I can't really justify yet more glue on top of cyano and pva!

Jonathan - I'd suggest a bit more foam to surround the battery - at least a complete wrap. Might be my eyes but it looks like the airframe is in direct contact with the cells? In most cases I would put in two light 1/8 or 3/32 formers across the width of the fuselage and just stuff it full of foam with the battery in the middle of it - total overkill? foam weighs next to nothing and there's no danger of the thing coming loose. here you could put two rectangle formers either side of the switch, then stuff that whole switch compartment with foam...

Hello and welcome You said there are 10 people working this project - which aspect of the design are you responsible for? What other design goals does your team have?