[canadianice]

Haveing built two of them myself I think I have worked out he problem. Both where underpowered. Twins are buy nature larger than our single seat fighters larger planes have more drag and weight. Two 15's can not get the speeds needed to compete in WW2 and you wind up being chased by every one. Before you say well get a better engine. I did,OS CVA's, they cost more than our FX's 50% more and will not turn bigger than an 8/4 prop. I am proposing that we let 25's that we already have be used in them and see if that will get more of them to built and flown. Will they be faster yes, are they going to be faster than our single's dont know yet. I am building the twin Mustang and will be using 25 FX's in them to fly at our Sunday scrambles will let you know how it works and the reaction of the guys who fly agianst me.

[Patch]

I like that idea. faster, yeah, but harder and more expensive to build too. Maybe putting a prop limitation on it would satisfy the nah sayers.

[Buzz]

Well, here's the nay sayer.

Maybe the problem is that all the other planes are getting too fast.

I believe, just as it is written in the rules, the objective of WW2 scale combat was to recreate WW2 era combat. It seems that we have an unsatiable need for speed in this class, far exceeding scale speed for these planes, which should be at best 40mph. To me this matters in the sense that it takes away from the scaleness of the class. There are no rules governing speed in this class, but I personally think it is not in the spirit of the intent of the class. There is a class for this however, and its called open B.

In Europe, WW2 combat is alive and well. They use .20 size plain bearing engines and seem to make it work just fine.

But I digress. Aside from my little rant, here are some points to consider:

* An OS.25FX engine spinning a 9x4 APC prop at 18000rpm, produces about 6.38 lbs of static thrust (just shy of twice the maximum weight allowable in the class)

* An OS.15LA spinning an 8x4 APC prop at 17000rpm produces 3.55lbs of static thrust, thus a twin would produce 7.1lbs of static thrust. Considerably more than a single OS.25FX.

* Wing loading on a P51 mustang weighing the allowable maximum of 3.5 lbs and having a typical wing area of 240 sq.in. is 33.5 oz/sq.ft.

* A typical p38 with an allowable wingspan of 57" and weighing the allowable maximum 4.5lbs would have a wing loading of 30 oz/sq.ft.

This is just an example, but here you have 2 planes with relatively the same wing loading, with the twin example having roughly 11% more thrust.

Our combat planes can already climb until they lose radio range. Do we really want to go this route?

This year I am focusing more on WW1 combat, but with the allowance of BB engines, I fear that class is headed for the same fate. WW1 was designed to be much slower, with pilot skill, "E" management and calculating your engagements mattering more than chasing a plane down.


Just my opinion.

[Bent]

Jeff
You're supposed to slow down a little after getting married! Warbird twins are very cool and I've had a P-38 on the back burner for years. I'm willing to bet an FX powered twin won't be much faster than a single. With the extra weight it definitely won't be as manouverable. Looking forward to the flight report.

[canadianice]

Yea I know I think it is mid life chatching up with me. I just bought a Mecedes CLK 320. You want to talk fast. Point well taken, I'm going to bulid it any way and use it for demo's and Sunday scrambles.

On the WW1 side of things, I am building an other DR1 for Jeff Decalawy I am using undercamber airfiols and increasing the wing cord 1/2 inch 3 degrees of positive incedence in the tail [first ones flew with a ton of down trim]. hope the under camber will help with slowing it down some and giving more lift. as this one tends to come out on the max weight side. then maybee I can slow it down some. The pusher was probably the sowest flying plane at the meet the other weekend and it took the most cuts. Mind you in the hands of a rookie disaster it flies about 10 mph above stall so you realy got to manage your manovers.

Ted came across some great wheels for WW1 at Wall Mart, they sell baby strollers for 12 bucks and you get 8 wheels that are mint should make landings better.

[godfrey]

Hey Dan,
How'd you figure out those figures for thrust? It's interesting that a .15 can produce enough thrust to fly a 3.5 lb airplane. Makes me want to try it so i can hide the engine in the cowl better!
I think you and I have had this disscusion before: the .25 versus .15 debate.
The Fokker d-8 spad that I'm doing weighs about 1.2 lbs (without radio gear) so my .15 should be able to pull it around no problem. I was wondering if it was gonna have enough poke to do the job..
Greg

[Buzz]

Greg,

I used the thrust calculator algorythm that's available on our website, in the library section under "other documents".

These are static thrust figures, and we are talking at maximum RPM. Even if the figures are off somewhat, they are good for relativity. It allows you to put 2 case scenarios in there to compare the results.

[Midairplarina]

Hey i got a p38 on the go for JEff as well soem day ill finish it hes got to cva .15 for ti so it should be just fine..

[Ryan]

Hi that P 38 is Crapppp LOL No it look's Sweet

[Gert]

I flew my some years old JDB-kit Lightning with OS LA.15 engines in the biggest European contest at WASG in Znojmo Czech Rep. last summer.
Engines turned with APC 7/5 props and 25% fuel nearly 17000 Rpm ( limit here in Europe), plane was fast as the fastest single engines here. In first round where I used the P 38 one enemy was Dan Pek - Cz Champ of 2004 with his quite fast Me 109 H with MVVS 3,5 engine. All planes behind my Lightning the did not get my streamer, after a risc attak of Dan I got his streamer, he not mine! But the singles have been more manuveral, the double only fast - and a beautiful picture in the air !I was the onliest user of a twin in contest, the Sweden had a very good Tigercat, but the did not use it in contest. A foto is on ACES Slovenija Foto WASG 119 1970
Watching your forum always with interest -
regards G e r t NC of Austria