Experimental build - 1.7m wingspan F8F Bearcat

[Simon Chaddock]

I still favour planking, ship building style, for complex curved fuselage skins. As long as the formers are the correct shape and size the final curvature is a smooth transition nose to tail.

Some sanding to completely smooth the plank joins and that's it.

This AN2 fuselage has substantial flat areas. It almost like building in balsa old style except 3mm sheet foam and printed formers in this case.

First formers.

All the formers.

The skin complete.

Maybe not everybody's cup of tea but it works for me.

 

Edited June 25 by Simon Chaddock

[Lipo Man]

9 hours ago, Simon Chaddock said:

I still favour planking, ship building style, for complex curved fuselage skins. As long as the formers are the correct shape and size the final curvature is a smooth transition nose to tail.

Some sanding to completely smooth the plank joins and that's it.

This AN2 fuselage has substantial flat areas. It almost like building in balsa old style except 3mm sheet foam and printed formers in this case.

First formers.

All the formers.

The skin complete.

Maybe not everybody's cup of tea but it works for me.

 

Looks to work really well. I will almost certainly try that next time…

[RICHARD WILLS]

13 hours ago, Lipo Man said:

Had a break from this project because the retracts for me Warbird Replicas FW190 arrived in the post, so I needed time to fit them then even more time enjoying flying it!

Anyway, I’ve started on the exterior skin of the big Bearcat. No plans for this - it’s a trial and error fit and trim operation so a slow process and the finish will be poor up close. However, as it’ll be in the air and moving that won’t matter. The intention is a big cheap plane that looks good in the air and doesn’t need to win any scale competition prizes close up!

I really would like more people to have a go at this sort of "evolving own design " . 

Foam board or depron is dirt cheap so size is not an issue . The inner box body is perfect for test flying and also makes lining up tail and wing , plus sorting the balance point all easy and flexible until you know it flies . 

When you consider that there are loads of cowls and canopies available for traditional scratch building , the possibility of "guiding the lily " later is available to everyone . 

The flite test models are exactly that and can look a bit basic , but once you add some decent plastic parts and a spinner they look much more up market . 

Here is a picture of my Flite test P38 which looks way better than the standard kit with cardboard canopy and cowls . 

 

[Lipo Man]

2 hours ago, RICHARD WILLS said:

I really would like more people to have a go at this sort of "evolving own design " . 

Foam board or depron is dirt cheap so size is not an issue . The inner box body is perfect for test flying and also makes lining up tail and wing , plus sorting the balance point all easy and flexible until you know it flies . 

When you consider that there are loads of cowls and canopies available for traditional scratch building , the possibility of "guiding the lily " later is available to everyone . 

The flite test models are exactly that and can look a bit basic , but once you add some decent plastic parts and a spinner they look much more up market . 

Here is a picture of my Flite test P38 which looks way better than the standard kit with cardboard canopy and cowls . 

 

I’m not even slightly surprised that your Flitetest build is the best looking version I’ve ever seen. That is quite the inspiration!

[Lipo Man]

This week I’ve got the fuselage exterior mostly done - which means I’ve got the first opportunity to put the big bits together to see how it’s looking. As it’s intended to be a cartoonish scale build I’m pretty pleased - and the size is exactly what I was going for. Hopefully that will give me the inspiration to push on and get it flyable!

Does anyone know an easy way to make a clear canopy?

🤔

 

[RICHARD WILLS]

You can do a lot with a 2litre Coke bottle . Have a look at a chap called Julius Perdana on you tube .

I imagine that a P47 Thunderbolt canopy is pretty close in shape. 

Belair do a 70" Ziroli P47 which would have a similar canopy . 

[Futura57]

This is how I mould simple cowls and canopies from plastic bottles. I hope the link works.

 

Plastic Bottle Moulding.pdf

 

 

[Lipo Man]

1 hour ago, Futura57 said:

This is how I mould simple cowls and canopies from plastic bottles. I hope the link works.

 

Plastic Bottle Moulding.pdf 1.03 MB · 11 downloads

 

 

The link worked perfectly. Thank you - this looks to be just what I needed!

[Lipo Man]

The moment of truth… I cut away the fuselage to allow the wing to be mounted properly, so everything is now bolted together. Putting a pair of 2600 4s batteries in the nose (they will run in parallel) allowed me to tip the plane inverted and check the CG - and it’s sitting about where I wanted it with no added nose weight. Hurrah!

So - all up weight nearly RTF is 2.49Kg which (if my calculations are correct) gives a very low wing cube loading of 5.3. I think that weight is pretty low for a 1.7m wingspan warbird (albeit a belly-lander) that’s not unexpected. Should be an absolute pussy cat!

[RICHARD WILLS]

Pussy Cat ?

😁I don't think Grumman did that one . 

[martin collins 1]

On 26/06/2024 at 11:51, RICHARD WILLS said:

Here is a picture of my Flite test P38 which looks way better than the standard kit with cardboard canopy and cowls . 

That looks very impressive Richard, it shows what can be done using your adding detail and weathering techniques, i bet that most if not everyone wouldn`t have thought that the P38 was a foamboard/depron model.............

[Graham Davies 3]

22 hours ago, martin collins 1 said:

That looks very impressive Richard, it shows what can be done using your adding detail and weathering techniques, i bet that most if not everyone wouldn`t have thought that the P38 was a foamboard/depron model.............

I think this is an interesting point Martin. Most people have a perception of foamboard or depron. Whilst the techniques may be different, there is a whole spectrum of outcomes from simple and functional up to full scale beauties. For me, it’s been like the light of building fun has been switched back on. 
 

Again, and shamelessly as I’m really proud of it, my depron 1/6 scale mk1 spitfire…

[RICHARD WILLS]

Graham . With the cost of balsa being a factor on sheeting larger models, can you expand on your experiments with adding a hard skin to either depron or foam board ?

Traditional balsa and brown paper covered models are very robust , so how would the chaps make their foam skinned models as tough ?

I know you have tried various off the shelf products .

[Lipo Man]

4 hours ago, RICHARD WILLS said:

Graham . With the cost of balsa being a factor on sheeting larger models, can you expand on your experiments with adding a hard skin to either depron or foam board ?

Traditional balsa and brown paper covered models are very robust , so how would the chaps make their foam skinned models as tough ?

I know you have tried various off the shelf products .

The Bearcat is currently so light I’m tempted to try fibre glassing. Ideally with a water based system but epoxy if all else fails. I’m hoping to re-maiden it this weekend if I can get the FW190 take-off dolly adjusted in time. 
Has anyone used lightweight glass cloth with water-based varnish?

[Graham Davies 3]

15 hours ago, RICHARD WILLS said:

Graham . With the cost of balsa being a factor on sheeting larger models, can you expand on your experiments with adding a hard skin to either depron or foam board ?

Traditional balsa and brown paper covered models are very robust , so how would the chaps make their foam skinned models as tough ?

I know you have tried various off the shelf products .

I haven’t yet got them as tough as a balsa or veneer skin, but mine are reasonably tough. The spitfire is covered with lightweight glass cloth applied with b&q water based varnish. It’s cheap and easy and provides a reasonably tough surface. The underlying foam is soft though so it’s still easy to mark.

 

For the replacement wing on the p51 I used foamboard and left the paper on the outside and then glass clothed over this. It’s a little tougher still. Certainly into practical scale model territory.

 

i think there may be further gains trying heavier cloth and possibly some tougher resins, but so far results are good.

[Graham Davies 3]

11 hours ago, Lipo Man said:

The Bearcat is currently so light I’m tempted to try fibre glassing. Ideally with a water based system but epoxy if all else fails. I’m hoping to re-maiden it this weekend if I can get the FW190 take-off dolly adjusted in time. 
Has anyone used lightweight glass cloth with water-based varnish?

Yes, it works really well. B&Q varnish doesn’t damage the foam, and dries reasonably hard. You’ll need 2 or 3 coats. With the spitfire I sprayed a coat of silk over the top of the paint too to give it a nice even sheen

[Lipo Man]

 

A trip to the field this morning and the weather was fine for a maiden. A quick taxi test on the takeoff dolly showed power on 4s was more than enough, so full throttle and full up elevator and away she went!

Flight performance was as I’d hoped - the light weight and large size made for slow and realistic manoeuvres. Rolls are very slow, but elevator response is more than adequate and she is very stable and easy to fly. 
I flew two flights. The second was for 6 minutes with some rolls etc. and on landing the two 2200mAh 4s batteries were still at 54%, so eight minutes should be very comfortable!

Next flights will push the envelope a little to test inverted, loops etc. Really pleased with how she looks in the air. The slow flight looks very realistic - given the 1.7m wingspan and only 2.5kg weight ready to fly that was what I’d hoped for!
I’ve put some fibreglass onto a scrap of foam with some water based varnish I had lying around. If that works I will sand the airframe and fill the worst gaps before fibreglass and paint to finish. It will be very rough up close, but I think it will look great from a distance in the air!

 

 

[RICHARD WILLS]

I really like that . Excellent work and a very friendly flier .  You can tell that with that very light wing loading , even a retractable undercarriage wouldnt be a problem . 

Perhaps build a second wing ?

Just a thought . 

[Ron Gray]

1 hour ago, RICHARD WILLS said:

Perhaps build a second wing

Cor, a biplane Bearcat, now that would be something.

[Lipo Man]

1 hour ago, RICHARD WILLS said:

I really like that . Excellent work and a very friendly flier .  You can tell that with that very light wing loading , even a retractable undercarriage wouldnt be a problem . 

Perhaps build a second wing ?

Just a thought . 

I would never have thought of that before building your FW 190. Having done that I’m tempted, and as I was able to add those after the wing was completed I have to admit to having a little think about how I’d add retracts to this as well. Hypothetically speaking. 

[Graham Davies 3]

13 hours ago, Lipo Man said:

I would never have thought of that before building your FW 190. Having done that I’m tempted, and as I was able to add those after the wing was completed I have to admit to having a little think about how I’d add retracts to this as well. Hypothetically speaking. 

You’ll need to add a bit more “structure” to the wing to support the retracts, and a bit to the wing join to absorb the take off and landing loads. I use hardwood spars for the main spar, a secondary spar and liteply ribs up to the retracts. This prevents twist and gives a hard point to attach a ply plate for the retracts. I then make sure these spars are joined to tough points in the fuselage. Easy enough if you plan it out. Be aware, you need to add a bit of complexity if you want wheels!
 

it’ quite possible though. I fly off a quite rough strip and both the spitfire and my regianne have no problems.
 

let me know if you need any details.

 

Regianne for reference…

 

Graham

[Lipo Man]

As usual the few finishing touches are taking as long as the big structural bits! Two things I was quite pleased with this afternoon.  I’d intended 3d printing the front of the cowl, but my printer is playing up. Plan B - laminate strips of 6mm foam with foaming golden gorilla glue, using a paint can as a former. It was a random idea but it worked brilliantly! I’ll carve and sand to the final shape tomorrow after the glue has set. 
The other bits I was pleased with are the side cooling vents. They’re quite noticeable on the full size, and I need a way for warm air to exit the fuselage to cool the ESC and batteries. So I cut slits in the skin and pushed them in to mimic the full size. They look pretty good - I’ll finish them with metal self adhesive tape to mimic the full size - some seemed to have an unpainted polished panel around the vents. 
Last but not least, I had a go applying glass cloth to the belly cover. I used water based varnish which seemed to work well (not as stiff as with epoxy, but so much easier to do). I’d got a match pot if navy blue emulsion from Dunelm and this went onto the glass surface well - so I’ll repeat for the rest of the fuselage. 

[Lipo Man]

The Bearcat is getting closer to being “finished”. The fuselage is fibreglassed (with water based varnish) and has a first coat of paint. I’m already flying it to get used to it - not without incident! Some issues with the takeoff dolly lead to a punctured lower wing skin (after a nose-over) but it was an easy fix, and once I’ve got to the shops to buy some more glass cloth the wings will be more robust (photos of the damage and the repair below). 
 

However - once off the trolley it flies really well. I’ve increased the size of the ailerons by about 30% over scale as rolls were soooooo slow. But it flies slowly, smoothly and has plenty of power. 
 

My clubmate Scott filmed some chase footage with his drone this afternoon so here is some air to air filming to show it in flight!

 

 

 

 

 

[Lipo Man]

I’ve been flying the unfinished Bearcat quite a bit, so progress has been slow. However - some more things slowly getting ticked off the list. Paint is 80% complete after covering - a mix of fibreglass and brown paper. I’ve 3d printed a dummy engine and finally sorted out how to fix the belly cover in place. Getting closer…

 

[Futura57]

Still lacking an office though 😉