how do you manage weight to power / thrust?

[Marzipan]

some of the comments to @bisco about their Tiny Trainer and how the weight of the wheels they added would negatively affect it's performance. and on reddit, I followed along a thread on repairing a molded plane that crashed and snapped a wing off near the fuse. for the repair, different glues / epoxies were recommended as well as splinting it with carbon fibre rods, skewers or even toothpicks if they really wanted to keep any additional weight down. it was also recommended to do the same to the other wing to maintain overall balance.

assuming you have a motor that could handle more power, would you look to find a new balance with a bigger batter at a lower amperage to keep the same battery weight but be able to fly, even if it has less overall airtime?

 

[Monte.C]

Not sure exactly the question, but in the end it's not a complicated equation. Weight is always a factor. Let's just say you're flying a plane that'll tool along fine for you at 2s, but right away you want more speed & performance. Yes, No sweat to go to 3s as long as the motor'll be ok with 3s. Yes, for the weight issue you'll wind up with lower mAh - shorter flight time - but everything's a trade-off.

You buy a plane or build a kit or draw something and build it. You have a specific motor/prop in mind, and that motor is happy on 3s or 4s. Take it from there.

 

[Marzipan]

@Monte.C well, if I shorten my ask...how do you deal with the additional weight coming from repairs?

 

[Pieliker96]

some of the comments to @bisco about their Tiny Trainer and how the weight of the wheels they added would negatively affect it's performance. and on reddit, I followed along a thread on repairing a molded plane that crashed and snapped a wing off near the fuse. for the repair, different glues / epoxies were recommended as well as splinting it with carbon fibre rods, skewers or even toothpicks if they really wanted to keep any additional weight down. it was also recommended to do the same to the other wing to maintain overall balance.

assuming you have a motor that could handle more power, would you look to find a new balance with a bigger batter at a lower amperage to keep the same battery weight but be able to fly, even if it has less overall airtime?

Realistically you won't really notice ±5%-ish in weight, which most repairs are likely to fall under. Changing batteries to offset the weight and give a higher power/weight is an option, but you could also just choose a larger or more aggressively pitched prop to make up the difference.

In any case foamies typically have plenty of margin in both wing loading and power to weight ratio. The most you'll feel after a repair done proper - besides maybe a slightly slower acceleration or slightly higher stall speed - is having to retrim the airplane.

 

[Monte.C]

@Monte.C well, if I shorten my ask...how do you deal with the additional weight coming from repairs?

Yeah for me - and I fly small-ish planes - a bunch of Gorilla Glue and a couple bamboo skewers hasn't made much difference. It's easy to overpower these planes anyway, with today's electronics, and that's the way we like them. Lot's of wiggle room there.

Like in a lot of designed systems, you strive for absolute care and perfection at every step along the way (like in weight savings and aerodynamic characteristics) and then at the end you know you're ok to just take care of the last couple things in a more scattered fashion, like when you need to repair the plane.

 

[Merv]

...how do you deal with the additional weight coming from repairs?

Eventually the weight of the repairs adds up and will affect the performance, then it’s time to build another. I usually get 3-4 major repairs on a plane before I retire it, I don’t keep a count of minor repairs.

 

[quorneng]

The weight of repairs does depend on the structure of what you are repairing and the methods you use.
Do you need to 'splint' a break at all or can just a simple glue joint suffice? It depends on the type of foam and the glue used.
With a solid foam structure it is the surface layer that is under the greatest stress so a surface 'bandage' over the break can actually restore full strength for a tiny weight gain. The 'cosmetics' of a repair is a skill as well.

 

[Monte.C]

Ah, put some glue & a stick. It'll be fine.

 

[Hondo76251]

Only time repairs have been a problem for me is when im being lazy or in a hurry and i use hot glue. That can add up, especially if its in the tail area, but i mostly use white gorilla glue and packing tape. Weight after repairs is pretty minimal.

As long as you keep the CG correct you have a pretty large margin for overall weight.

 

[mastermalpass]

@Monte.C well, if I shorten my ask...how do you deal with the additional weight coming from repairs?

My Su-34 accumulated a fair amount of glue and lolly sticks over its career and its flight performance showed no noticeable difference. My philosophy is just build with a ridiculous amount of head room. Most of my foamies have enough power to climb directly up at 90º and can gently cruise by at 20mph or less. So when my 350g Biplane suddenly took on an extra 56g camera, it was hard to tell the difference. When my 290g Halfpipe took on the same weight, the CG was shifted lower and made it extra stable (a little too stable for my liking).

WHERE the weight is, makes a difference though. So I also like to leave lots of space in the battery tray so I can counter-balance anything offset without having to add dead weight. Though even cosmetic repairs on wings only really needed trimming out.