Topic: BT 1/6 scale F4U Corsair

Hello gents...

I've got a little head scratcher for you...

The real F4U Corsair had 2450 hp engine and weight (loaded) 6653 kg (14669 lb)... That gives us power-to-weight ratio of 0,368 hp/kg or 0,167 hp/lb...

If my 1/6 scale Corsair ends up with (for discussion's sake) 9 kg or 20 lb (I'll try to keep it lower ) and I get a DLE 30 with 3.7 hp, I would get power-to-weight ratio of 0,411 hp/kg or 0,185 hp/lb...

Is it possible to make calculations like that for scale models or I got it all wrong...
I don't know why, but 50 cc engine seems a bit too big and overpowered for a model like this (80+" wingspan)...
I'm not looking for unlimited vertical performance, just normal flying characteristics...

I'm certainly no expert, but this how I look at it:

Bear in mind that the real thing would probably just take off fully loaded with fuel and ammo.

Also, you can't scale the grass or the bumps down. A bit of extra power is no bad thing, really.

Plus, the larger engine gives you a more scale sized prop.

Well, I know that a bit of extra power can't do harm, but I'm concerned if 50 ccm engine would fit inside the cowl... It would be a real shame to cut a 2" x 2" hole in the cowl for cylinder head and spark plug to stick out... So I could go for a 40 ccm petrol swinging a 20" prop...

hello gents...

it's been a while, but the build still goes on... I managed to catch few spare hours during the Easter weekend and I made some progress on my Corsair...

Elevator and rudder skeleton has been finished, along with lightening holes cut on the elevators, which are now ready for further sanding to the desired shape and sheeting with balsa... I still have to cut lightening holes on rudder... I also played a bit and put and glued all the parts I've done so far with masking tape to see how it will look...

Hello gents...

This build went far on from the last time I posted...

Forget about layers and stuff I've been writing about, it didn't turn out well, so I learned my lesson.
I have already started to make new tailplane, fin, rudder and elevators...

Wing skeleton is complete and port side flaps are hinged...

Port aileron is also complete...

Retracts are 90% complete, I'm still waiting gears for turning to be made... (I didn't take any pictures of them, yet)...

more pics...

I don't know why, but I am allowed only 2 attachments per post...

Excellant, I'm glad that you've carried on with the build.  I'm building the 109, his models and plans are easy to follow.  Keep it going!

BB

Hi mr. BB,

thank You for Your post.

Hi all,

the build went on, but unfortunatelly my camera is broken, so no pictures for now.

Being the beginner, I made many mistakes when I started the build so now is the time to make corrections. As I said before, new tailplane, fin, elevators and rudder are being made, because the ones I made are too big (as my plan copying was not very proficient). Tailplane skeleton is done it just needs to be sheeted, and I cut some of the fin half ribs.

All 6 flap segments are hinged and it took me 3 days to hinge them properly (dad helped me with hinging). Due to mistakes made before, hinging was not entirely scale.
I also hinged ailerons, again not entirely scale, but I'll make dummy hinge covers and it won't be that noticable.

That's all for now, more work waits tomorrow.

cheers,
Robert 

I managed to take some pictures with my mobile phone...

 

and one picture of bits for retracts...

Rob,
Its going well, I hope that you manage to keep going with it. I'm having trouble with the flaps on my 109, I can't get the correct movement with servos, I changed from bell cranks to make it easier.  It isn't.

I'll keep going, I hope ou do too.

BB

Hi mr. Bucksboy,

yes, I learned myself that some things are best kept as great BT drawn them... 

The build goes on, but unfortunatelly very slow due to my studying.

I run some pushrods through the wing ribs and I learned that steel ones are way too stiff for what I need them, so I will order some Sullivan Gold-N-Rod semiflexibles... but will stay on bellcrank system...

unfortunatelly, I forgot my camera at my girlfriend's so I wasn't able to take any pictures...

I'll try to take some pictures for the Easter weekend...

Where can we see your 109 pictures?

Cheers,
Robert

I hope this has worked!  This is my 109 at present, still sorting out the cotrol surfaces before I get any paint on it

Thanks

Bucks

Nice...

Hi all

Sullivan semiflexibles are in so I ran them through the wings and I am very impressed with lack of friction...
I also sheeted fin and tailplane halves and glued them together... now I'm waiting till the morning to remove the clamps and to see if it is all OK... I also sheeted one elevator but forgot to take pictures... 

That's all for now

Cheers

hi all.

it's been a while since I posted my progress. I just couldn't find all the time I would need. I had few short periods of free time this summer when I could attend to my build. You'll see results in pictures.

I threw out belcranks and semiflexibles because I got big slop, so flaps couldn't retract all the way. So I placed servos right behind flaps to get desired flap movements. My father cut some grooves in spars, so I can reinforce them with come carbon rods + epoxy. 

more news soon... 

hi all.

Just a quick question here. I'm planning to reinforce the robs between which I have glued servo holders. Would it be enough to reinforce them just from the outside with glass cloth + epoxy? Or should I use carbon cloth, or kevlar, or carbon - kevlar hybrid cloth?

Are you going to be able to access and remove a servo if/when necessary?
Servos are very reliable today but I would hesitate to completely bury a servo, especially in a scale model.

I usually reinforce the ribs with triangle stock along the servo plate and rib junction, but seems you used very thick ply plates so maybe the plates themselves are enough?

Hi mr. Erez, thank You for Your reply.

Yes, I will be able to access servos, I will make service hatches, which I'll try to incorporate into panel lines to achieve desired scale details.  Service hatches will be detachable via 4 small screws at corners, which I'll try to incorporate into riveting scheme.
I used 10 mm ply, and I'll use triangle stock, as You say, because a bit more strength goes a long way.  Still, I'll reinforce ribs themselves with some glass cloth + epoxy.

How's it coming along?

very, very, very slowly... 

since I made some foolish mistakes I have to make some things again. also, studying doesn't help me either... 
this weekend I'll go home and spend some hours on Corsair. New ailerons are half done, but I didn't take my camera to take pictures...

cheers,
Robby