ESM Bearcat - powered by Laser

[Ron Gray]

[Ron Gray]

Another non blog thread based on the build that I'm just completing on the Bearcat. As per the title, it's an ESM offering and I think one of the last, judging by the mixed bag of missing and doubled up components in the ARTF 'kit'. Also, as per the title, it will be powered by a Laser 240v twin.

I bought the kit about a year ago and got stuck in with the wing assembly which was fairly straightforward despite missing bits such as the locating dowels and the wrong plastic gear bay housings. I didn't take any photos of this part of the assembly as it is much the same as other ARTF's. I then mounted the 240 to the bulkhead, mounting it upright to ensure that the feed lines to the carbs were not above the carbs. At that point I put it to one side as there were then lots of fiddly bits to do which I didn’t face doing!!!

Edited By Ron Gray on 17/01/2020 09:57:06

[Ron Gray]

Roll on about 10 months and I swept off the cobwebs and got back into it. Modified the tank to have 2 clunks and mounted that to the servo shelf, mounted the servos then go to grips with the rear end of the ‘plane.

[Ron Gray]

This turned out to be a long process, the tailplane fixings were missing from the kit so I had to make up my own elevator mounting pins and spar tube. The supplied tailwheel assembly was a bit rudimentary so I decided to fit my own which, although still not true scale, looks a lot better than the supplied coiled wired job. The wheel itself is really too big for scale but it does allow for some suspension via the tyre. The actuating mechanism for both the elevators and rudder are hidden within the fuse and although the elevator one is straightforward and easy to get at the one for the rudder definitely isn’t. The instructions for this left a lot to be desired in fact if I had followed them then I wouldn’t have had a rudder connected to any servo! No access holes had been allowed for in the fuse so I ended cutting out a chunk from the underside so that I could feed the actuating mechanism in and then fitted a hardwood block to the bottom of the fuse as a bearing block for the control rod. After connecting the pull pull wires I was then able to fit the mechanism in place and then sheet in the cut out I had made. A mistake that I made at this point was not directly connecting the tailwheel steering arm to the rudder control arm. I had planned to use piano wire from the tailwheel to the rudder servo as this would give me some ‘spring’ to absorb shocks but when I connected this up and tried it out, the difference in height between the tailwheel control horn and the servo horn is too great and allows the wire to flex in the middle, and there isn’t a enough space for me to get inside the fuse to fit a support tube. In the end I opted for a small MG servo to control the tailwheel and whilst not ideal, being mounted at the rear end at least it works. I may revisit this arrangement later.

Elevator control

Rudder control with the hardwood 'bearing' block just visible at the top

Cut out to fit the rudder control subsequently filled and ready for final finishing (later!)

Steering servo and connectors Mk1

Covering piece and tailwheel in place

[Chris Freeman 3]

Nice project this and it should be a great flying aircraft as the ESM Stuff normally flies very well. Pity they lost the plot in the end as they were very nice kits. Look forward to seeing the progress.

[Ron Gray]

I agree with you Chris, they are / were decent kits and it's a shame they went belly up.

Progress (on this thread) should be fairly quick as most of the work is already done but there are still things to complete such as fitting the canopy. Other bits such as making the landing gear doors (missing from the kit as was the drop tank) will be left until after the maiden flight.

[Jon H]

I have 3 currently flying ESM models and another 3 to finish off.

All 3 of the flying ones are great fun with the La7 and Sea Fury being utterly super to fly. The P39 is not as easy to fly as the other two but my research indicates that it mirrors full size handling traits almost exactly.

It should also be noted that my La7 will be celebrating its 10th birthday in March which is quite astounding to me. The P39 and Sea Fury will be 7 and 6 years old themselves at some point this year.

The Bearcat is looking great though and it will be cool having it sat on the flight line next to the tigercat. Its just a shame you cant fly both together for some formation passes.

The only thing i would suggest you change is the tail wheel linkage as any impact will break it. You could try using one of these **LINK** spring setups to damp any impacts and protect the servo/mounts

Edited By Jon - Laser Engines on 17/01/2020 14:07:59

[Ron Gray]

Beat you to it Jon, I have already changed the linkage to this (as I said in my post above, this thread is more a record of what I have done, not so much what I'm doing!!)

[Jon H]

that will teach me to skim read

[Ron Gray]

My fault, too many words, but that's the problem when retracing 'history'!! It will soon be up to date though, a couple more posts and we'll be there. Here the wordy bits that I had already written to go with the piccy

I did revisit the tailwheel controls and decided that I needed some form of shock absorbing in place so I have removed the pushrods and replaced them with springs.

Edited By Ron Gray on 17/01/2020 15:38:42

[Ron Gray]

So that was the back end sorted, for now, my attention turned back to the wing. I had already machined and refabricated some oleos and they fit quite nicely in the wells. however, the wells themselves need work to them as they are just an open structure and my concern, if flown like that, would be the slipstream getting inside the wing structure and possibly blowing the covering off. As the plastic covers (mentioned above) don’t fit, I’m going to sheet out the wells with some thin balsa and that is the next job on the to do list.

[Ron Gray]

The wheel wells have now been closed in and painted to match the dark blue of the rest of the airframe, just got to fuel proof them now.

Edited By Ron Gray on 17/01/2020 15:42:48

[Jon H]

looks great to me. On all of my ESM/YT models i have ditched the plastic wheel wells and just painted/fuel proofed the wood. Why? Well the plastic things supplied are a total pain to fit. They also fit the wheels/legs so tightly that any slight tweak means the gear wont retract. The final one is that most WWII era fighters didnt hav sealed wheel wells. The BF109 had canvas bags to seal them, but most were just open structures so leaving the plastic liners out is actually more scale.

Truthfully though scale considerations are lower on the priority list and i mostly do as Ron has done as it saves so much work.

[Ron Gray]

Some more progress, cockpit canopy trimmed and fitted (I will re-do the cockpit interior when a) the maiden flight has been completed and b)when my 3D printer has been delivered and setup!)

Nose weight added to chin of cowl

Looks nice with the canopy and cowl in place

Nicely encloses the V twin

[Ron Gray]

Given the poor weather I’ve done some more work to the Bearcat and it’s now ready for its maiden!

Upgraded the cockpit with some 3D printed parts including a new pilot.

Plus decided to change the engine to a new Laser prototype 5 cylinder radial!

[Jon H]

At this rate i think model clubs country wide will be awash with new models come the spring as everyone has been forced into build mode!

Its looking great though and im sure it will go like a rocket. Is that a 17x6 prop in the photo? i couldnt quite read it. If so slap something slightly bigger on it. 17x8, 18x8 etc as it will rev like crazy on the 17x6

[Ron Gray]

Yep, this is my third ‘cat now ready for maiden, Tigercat, Bearcat and Hellcat.

Re the prop, well spotted and it will be changed prior to flying, as will the prop washers which are too large! IIRC I ran the 240 with an 18x10 in the Wots Wot XL and it pulled that along quite nicely. So I think that a 17x8 should give me the speed that the Bearcat is associated with.

[Jon H]

It should go nuts on a 17x8. I plan to use a 19x8 on the 240 in the hurricane but i am after thrust more than speed

[Artto Ilmanen]

Another great model, Ron!

 

Have you yet maidened it?

 

 

[Ron Gray]

Thanks Artto. I did the maiden flight last year but suffered a lean cut on take off, the resultant harsh landing ripped the u/c out! There isn’t a great deal of damage but I just haven’t had the time to fix the legs back in but more importantly I need to investigate the cause of the lean cut. This will mean stripping the fuel lines and tank out of the fuselage.

[Artto Ilmanen]

ok. Sorry to hear of your mishap! 😥

I’m building an ESM Focke Wulf and have been guessworking wether to use Laser 150 or 240V. I decided to go for the 150 as it’s about 450 grams or 1 lbs lighter than the 240V. Also, the 240V is probaly overkill for the Focke in terms of power. However, It would have been interesting to hear how your Bearcat flies with a 240V. A 3 blade prop might help with excessive power and lopk a tad more scale, too. By the way,  both models, Focke and Bearcat, are about the same size, hence my interest in your experience with the Laser 240v

 

Hope you will soon finish your other Laser powered models and can again focus on the Bearcat!

 

Edited February 4, 2023 by Artto Ilmanen

[Artto Ilmanen]

On 17/01/2020 at 22:10, Jon - Laser Engines said:

looks great to me. On all of my ESM/YT models i have ditched the plastic wheel wells and just painted/fuel proofed the wood. Why? Well the plastic things supplied are a total pain to fit. They also fit the wheels/legs so tightly that any slight tweak means the gear wont retract. The final one is that most WWII era fighters didnt hav sealed wheel wells. The BF109 had canvas bags to seal them, but most were just open structures so leaving the plastic liners out is actually more scale.

Truthfully though scale considerations are lower on the priority list and i mostly do as Ron has done as it saves so much work.

 

Have  you Jon experience any issues such as balsa covering stripping of due the airstream? Or any strange flying behaviour when gear down due to open structure causing some turbulence (potentially?)

 

extract what Ron's wrote: "..the wells themselves need work to them as they are just an open structure and my concern, if flown like that, would be the slipstream getting inside the wing structure and possibly blowing the covering off."

 

I'm not using the plastic wheel wells with my WSM Focke Wulf due to the very same reasons: more scale without them and they do not fit well in anyways. I'm tempted to save some weight & work and just paint and fuel proof the open structure.

 

 

[Jon H]

I have no noted any issues caused by removing the wheel wells. I have had issues with gear doors twisting into the airflow and that drag is felt, but no other problems. 

[Ron Gray]

2 hours ago, Artto Ilmanen said:

extract what Ron's wrote: "..the wells themselves need work to them as they are just an open structure and my concern, if flown like that, would be the slipstream getting inside the wing structure and possibly blowing the covering off."

My comment was related to the film covering, make sure that it is well stuck down around the edges otherwise the slipstream could rip it off. The supplied, rubbish, plastic infill pieces do cover that joint thus getting over the issue.