I suspect that you could have some tip stall problems at low speed with that wing... watch the ratio between tip and root chords.
I also strongly suggest that you make a weight and balances charts in order to place the wing properly and to recalculate better the tail volumes; also it could help to stimate final weight of the ship.
Cheers!!!!

Guille

PS: may be Mr. Daniel Raymer and his book could give some advices too!!!

Guille 2006

So, your concern is the excessive taper ratio, made worse by the leading edge sweep? While I agree the taper may have been over the top, and has since been changed.I'm not particularly worried about the taper ratio, most other competitive aircraft of the moment have taper ratios of around 0.46 which is spot on for what I have. Also I'm usng a slightly higher percentage thickness airfoil on the tip to reduce the tipstalling threat. While I realise I'll never acheive a true elliptical lift distribution, I have at least got a wing which doesn't peak out so much at the tip as before at higher AoA, due to the reduced leading edge sweep. Thanks for pointing that out.

As for the weights and moments, I have acutally got a weight table from the previous model (see post 1) and with some judicious juggling of battery packs and ignition modules my projected CG is acheivable.


If I've missed something though, please, do let me know, after all this is what this thread is for!

Curare

Hi Renegade;
Using hte plant view you posted I made a couple of rough number and ASSUMING UNIFORM FOIL THICKNESS came that you could have a wing tip stall before root stall... a very undesirable situation. For this condition the right taper was 0.49; you see? you're not really far.
Just 1.5% more thickness gives you a near uniform stall; so you're on the safe field now... or you can keep the thickness uniform BUT necesarily you need to round the leading edge (OK; it's not convenient).
If you want to go deeper on that (I really don't think we need it anyway) you can download from the MIT site the AVL software for making some analysis... it's free!!!
Keep posting;

Guille

Guille, yeah I didn't intend on keeping the same section throughout the wing, I just don't think it's very effective, and I do like the idea of having a thicker wing at the tip for structural reasons, hence we seem to be on the same side of the page here.

All I really need to do now is lock in a laminate and start cutting cores, but there is much reading to be done first, and possibly a few test panels to work with. It seems that in the case of the wet bagged discus launched wings, the biggest issue is not the aerodynamic stresses but "ding" resistance. The laminates can be exceedingly thin, but you'll put your find straight through the wing. I think at this stage this too, will be my biggest cause for concern.

Just out od curiosity,what engines would be used for this type of airframe? I think you have a great idea seeing how the price of Nitro will be more this year and maybe years to come.

I saw George Miller's Pentathalon powered by an OS 1.60FX converted to gas last weekend and was very surprised at the power it had. Certainly wasnt up to the 1.70DZ's, but more than adequate for most of the patterns. Especially on a fairly light airplane. Check out the Pentathalon thread and you can get some more info on it.

Arch

Yeah I have to admit the MVVS isn't quite up to a 170, so keeping the weight down is something of a mission for me, also considering I also have to cart around an extra battery pack and ingnition module it does add up. Having said that the economy of the fuel and how little it uses is brilliant, I can get 2 sequences of the advanced pattern out a 12 oz tank!

THe MVVS is a highly strung engine and does need a lot of love, I've gone through a few con rod bearings already, but I'm willing to do the work to get the power I need out of the engine..

AS for what type of engine could be used, I think any of the 140-160 2 strokes would work effectively with some judicious moving of the firewall to suit.