Xb 35 ? - RC Groups
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May 15, 2012, 07:25 PM
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Xb 35 ?

Just scanned a plan set for an XB35 From Model aviation circa '96
Dunno on the appropriateness of this. So it's only here as a Wee jpeg.
Also a couple of piccies of a semi recent and Exquisite xb35 model
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May 15, 2012, 07:55 PM
HerkS's Avatar
Interesting construct Bare

Can you read the dimensions. The resolution of the picture is not good enough for me to read the fine print

Thanks - Herk
May 15, 2012, 09:55 PM
Registered User
OK; I have good resolution images.. but discretion seemed the best path.
It's of 1/32" ! scale.
Original was a BIG plane.
wingspan: 64.5"
length; 17.5"
wing area ; 562.5 square inches
weight: : 46 oz ,
albeit using 4 Peck 'silver streaks' (ersatz S400's I would imagine) and 7 1500 NiCad cells
Even so the wing loading is just under 12oz /ft
Oddly, this model/build article used 1/32 sheeting which imo is too fragile/ thin.. legacy of the nicad cells and the cast iron motors I suppose.
The Lovely photo'd one is glass/epoxy laminated then covered in " Flite metal' .
A genuinely exquisite job .. well detailed too.
Something for me to aspire to :-)
May 16, 2012, 07:32 AM
HerkS's Avatar
I've been looking at the Northrop history quite a bit lately. Have been focused mostly on the N9M which was the test model for this big one.

The experiment I did with it indicated that the design wing twist of 4 degrees seems about right. I couldn't see anywhere on the plan an indication that it should have twist. It may of course have been described in the article - or it may be on the plan but I can't read it.

I also felt that working drag rudders would have helped a lot.

As drawn, the slot would be ineffective and probably would have actually detracted from the aerodynamics of the wing. Slots and slats need to contract toward the exit, and the exit needs to be aimed over the upper surface of the wing.

If you thought of building something like this, a slope glider version of the B-49 jet version would be a good starting point - avoiding all the weight and complexity of the power system. The basic wing plan layout would be the same.
May 16, 2012, 07:42 AM
You know nothing....
Stuart A's Avatar
Herks,3o washout indicated on the plan.I noticed from some photos of the plane the tip appears to be an inverted airfoil.Is that the case?This would give a wash out effect?
May 16, 2012, 08:01 AM
HerkS's Avatar
An inverted airfoil would have the effect of washout. So does up elevon trim.

Northrop however was adamant that his designs have symmetrical airfoils all the way from root to tip, so an inverted airfoil would not be scale.

On one of the N9M prototypes the part of the wing outboard of the elevon was used as a pitch trim surface. If some up trim was introduced to that surface it would look somewhat like an inverted airfoil. The N9M that has been restored, has drag rudders in that area. I think all of the bombers had drag rudders out there.
May 16, 2012, 08:57 AM
Closed Account
That looks quite interesting :-)

May 16, 2012, 09:14 AM
You know nothing....
Stuart A's Avatar
Herks,my mistake,it was the curve on the tip giving an illusion.

Jens,"that looks quite interesting"? You wouldn't be......or would you.
There's some really good pics first page of a google search.Xb35,HoXVIII-they'd make a nice pair.Both using Herks drag rudder system.
Regards Stuart
May 16, 2012, 10:13 AM
Closed Account
No no Stuart I have other plans right now ... but .... that is an interesting set of plans and ...

May 16, 2012, 11:44 AM
Registered User
more info that was illegibly on the plans image posted :
Washout is /was 5 degrees on this model
There are No rudders drag or otherwise, the Author claimed no instability issues . Presumably those 4 props add significantly.
Also the leading edge slots used in this plan, albeit of erm... reduced/simplified design were soon 'taped over' as they caused problematic drag at takeoff.
Stability is stated as good, allegedly a well behaved flying toy as no bad habits were encountered other that the typ sensitivity to CG issues.
But then rarely do any of these build articles ever mention much about 'aggressive' flying.. so that aspect often remains unspoken of... until trying it.
The full size paper plan (and article ?) is available from Model Aviation as 814 XB35
I believe that the shiny photo'd one...
was scratch built sans benefit of 'plans' :-)
Last edited by Bare; May 16, 2012 at 11:55 AM.
May 16, 2012, 11:36 PM
Retired CAD guy
birdofplay's Avatar
Found this pic out there
May 16, 2012, 11:45 PM
internet gadfly
nmasters's Avatar
The twist isn't easy to see but the blueprints say 4 degrees and the tip control surfaces are pitch trimmers with integrated drag rudders. They are not part of the roll control system therefor not elevons. The next surface inboard of them is the elevon and inboard of that is a landing flap. This arrangement of control surfaces is why I wouldn't recommend Northrop's control system. By cutting the elevons off short of the tips it creates induced drag that contributes to adverse yaw.

May 18, 2012, 07:43 PM
Registered User
erm what Are? you talking about ?
These plans say 5 degrees and ken's model is similar, albeit built entirely from 3 views Seemed to work 'just fine' by my observations.
Charitably: (I could do far worse :-) Real Life is a whole world away from theory, picked up gawd knows where.
As example:13 year old Boys have lotsa theories re Sex... I know I certainly did :-)
But often (usually bungle the reality.. when the rubber meets the road.. speaking figuratively... certainly true the first few times for most of us :-)
May 18, 2012, 11:41 PM
internet gadfly
nmasters's Avatar
Originally Posted by Bare
erm what Are? you talking about ?
Note the caption under Bob's picture of the N9-M
May 30, 2012, 04:03 PM
Registered User
TRP's Avatar
I just ordered a set of plans from: http://www.modelaircraft.org/plans/plans96.aspx

24.00 - for the two plan sheets plus the construction article
Half price for a second set.
Shipping is 9.00 (Flat rate)

AMA members get 10% off.

Now I need to find someone to laser cut me some parts. Brian - are you listening?

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