ErikElvis

My Feedback: (2)

Hey guys. I goin to make a battery tray for my sundowner that will be further back in the fuselage. I planned on hardening th e stringers first with some thinned epoxy. Then place a hardwood square runner on top of the stringer on both sides. Then adda tray between the stringers for the batt to mount on. Final step another hardwood runner epoxied in on top sandwiching tray between them. Think thst sounds like a plan?

Thanks,
Erik

MetallicaJunkie

for this particular application, it will work

Spitfire222

I'm not sure what you plan on setting up from your description, but I wouldn't use thinned epoxy to "harden" anything. If I'm not mistaken, that will only had weight, not structural support. Maybe add cross members between adjacent stringers, and then simply add the tray. If you feel its not stiff enough, add some extra support pieces of wood I suppose...

jetmech05

edited by jetmech

j.duncker

My Feedback: (2)

YUP THAT WOULD WORK.

Personally if I need to "harden or stiffen balsa" I use thin cyano. then glue stuff in with epoxy. Seems to stick ok.

TedMo

I just don't see the need to go for all that to provide a place for the battery. All you're doing is createing extra work and weight. Just wrap battery in foam and stuff it where you want it.

jaka

Hi!
Will work ...but why? when you can use CA glue and balsa...much lighter!!

OffroadBEAR

My Feedback: (2)

That'll work, but you really don't need to harden the stringers with extra epoxy and you really don't need the runners either. Extra epoxy will add strength but at a weight penalty, the strength is unneeded, and thus, the weight penalty unjustified for strengthening them with epoxy. When you epoxy in the tray, the epoxy added for this will provide enough strength.

Honestly, it sounds like you're wanting to add too much wood. If you are adding a ply tray that runs across the fuse sitting on top of a left and right stringer, just epoxy it down to the stringers and call it good, there's no need to add the extra wood (runners) and hardening epoxy, thats extra work and weight for pretty much nothing. Make the tray out of thin light ply and it will serve as a tray and a cross member without adding more wood than needed. Your efforts should be more concentrated on making sure the battery cannot come loose from its aft mount, that will definitely cause you problems during flight (shifting CG/longitudinal imbalance and/or loss of radio power).

Edit: If I were mounting a battery in the aft fuse (sounds like it from the OP), I would want some sort of tie down point, I would not want to rely on foam alone to keep the battery placed in the aft fuselage because if it shifts too far forward (the fuse cross section gets wider going toward the front and there would be less resistance to the foam moving, making it easier to shift as it went forward) the CG could shift drastically causing loss of pitch control. I recently lost a plane from such an occurrence (didn't have the battery held securely enough and it got loose from its mount).

ErikElvis

My Feedback: (2)

Its for the sundowner 50. It already a bit nose heavy as the 91 surpass is a little to big for the plane. Only way to not add dead weight is get that battery behind the wings. There is no room for adjustment anywhere else. Thanks guys. And to secure the battery I was going to cut a couple "dents" or slots in the ply wrap the battery in faom and throw velcro all around it. When Im done with it Ill mount everything but the battery and see how much weight I can play with.

I was just afraid of those stringers. They feel very soft and I wouldnt want any high g maneuvers to break them out with the weight of the tray and battery on them.

ErikElvis

My Feedback: (2)

Well after about 2 hours of sitting here going through different plans I decided to Ca the stringers to make them a little less soft. Then Im going to epoxy a sheet of balsa ply across them. I will then add a couple strips of 1/4 in hardwood squares on top to make sure it stays in place. I slotted the ply so I can run velcro around the batt and will run a zip tie in the other direction. I have only a small space to work with and this seems to be the easiest set-up for me. We'll see how it goes.

ErikElvis

My Feedback: (2)

Well in case anyone cares its in. Seems to hold well. It literally took me 25 mins to get the battery on it and strapped in. I hope it doesnt go bad for a long long time. I would have to remove two servos and work in a space as small as a roach motel. What a PITA. Time for giant scale...

Oh and should I use blu loc-tite for the engine mounts?

OffroadBEAR

My Feedback: (2)

Don't worry about the lock-tite. Just put some lock washers on the engine mount screws and everything will be good. If it will make you feel better, you can locktite it, but if you do, use allen head bolts so you won't strip them out when you want to remove the engine.

Hey, I care, I hope it works out better this time than last. I know battery installations can be a huge pain in the rear. I spent about 40 minutes trying to place the battery in my tail-heavy 4*, it sucks.

Did you fuel proof the forward fuse?

ErikElvis

My Feedback: (2)

Ha about 2/3rds of the plane is fuel proofed. I found an additional problem with the tank though. When I put the canopy on it would tilt the tank forward rubbing the fuel line on the hole in the engine mount. I used the dremel and added a notch to the hole so the bottom line has plenty of clearance. It needs to be ready tomorrow. I have a fella with a lil toni and a midget mustang goin up with me. If the thing runs with no glitches I should have them. The toni has a 1.08 OS and was faster than my minnow but at probably a pound lighter the downer should take em out. Oh and the mustang is running a Evo 61. The ol downer better do me proud. But I still cant wait to get my new minnow built with the YS 110.

opjose

Everyone is always complaining about how much weight thinned epoxy would add... you should really try measuring the difference sometime... I have...

You could coat the inside of a fuse ( I did ! ) of say a .40 or .60 sized trainer, and you end up adding a WHOPPING .5 oz to the whole plane...

Sheez, a lot of extra weight, yeah right....

For a small light plane, this MAY represent a lot of weight, but for something like the Sundowner, go for it...

JohnW

My Feedback: (6)

0.5 oz?!?!?! You know how much a pattern guy will pay to ditch 1/2 ounce? Probably $200-$300.