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  2. GU vs LS-1 (was Re: Q-talk 155 . . . .)

Re: GU vs LS-1 (was Re: Q-talk 155 . . . .)

Gary McKirdy
 

Hi Folks,

Sticking to the issue of structural strength alone, I know of 3 LS1 canards
on tail dragger Qs where the carbon spar did not fail during heavy landing
but the top skin delaminated (compression failure) from the foam core
approximately 1 foot from the fuselage in a chord wise bubble. The lengths
of this bubble varied between 4 inches to over a foot of chord. I have
never seen this mentioned before but suspect it must have happened in the
US as well as UK.

I deduced the weakness in the LS1 is the thin compression (top) skin which
can buckle before the spar breaks. Having seen this, here is a potential
solution.

If I was building (or repairing) one I would include on the canard upper
surface 3 "T" section layups made from bonding 2 "L" shapes back to back
about 1 inch on the vertical and 1 inch on the top horizontal when bonded
together set in to the foam span wise in to a shallow maximum 1 inch
straight hacksaw blade cut made in the foam at the root from the fuselage
tapes outboard about 2 feet in length. All 3 ends of each T can be tapered
about 5 to 1 to reduce stress transfer at the ends. If they were set 3 to 4
inches apart chord wise centred at 50% canard chord (excluding elevator)
this problem could be addressed.

The purpose here is simply to give the thin canard upper skin a better
surface area to bond it to the foam to prevent this tendancy to delaminate.
I would sand a gentle rebate for the horizontal of the T to sit in to keep
as smoth a cross section as possible. Flox it all in, peel ply or sand
later and let cure before laminating the skins on. The skins should now
stay where they belong. No known downside but use at your own risk.



Regards
Gary

On Tue, Oct 30, 2012 at 6:31 PM, Mike Perry <dmperry1012@...> wrote:

**


Hello all:

I have wondered for a long time, has anyone documented the performance
difference between the GU and the LS-1? and the difference between the
GU with Vortex Generators and without? wind tunnel data? anything?

I think if I was building a single seat Quickie I would use the GU
canard but not otherwise. I suspect either airfoil is better than most
other airfoils. But I have no data to compare them, and no data to
compare the the GU with VGs to the LS-1. I think wind tunnel data
exists, but it doesn't include the VGs. I think you are crazy to fly
behind the GU without VGs (Murphy will get you!).

Anyone got some numbers?

Mike Perry
ps: I agree with Sam re the Q2 but not sure about the Tri-Q.

On 10/29/2012 6:01 PM, Trevor Fernihough wrote:

Hi folks,
Two question for the group of folk who have built and are flying /
have flown their Q's.

I have cut the foam previously (years go in fact) to build the Canard
as a Q2. Subsequently I decided to go in the direction of the Tri-Q
and bought the kit including the new templates for the LS wing, carbon
fibre spars and undercarriage. The undercarriage is now fitted to the
fuselage. When looking to recut the foam for the canard, it is evident
that the new profile just goes outside of the already cut foam,
leaving me to have to get new foam blocks (no simple matter here in
Australia).

First question: Listening in on your chit chat, leads me to believe
that the GU is a more efficient wing than the LS canard, and that by
installing vortex generators on the GU, I would have the more
efficient canard without the contamination deterioration issue.

Have I interpreted the facts correctly in that regard ?

If so, then the second question is: To use the previously cut GU foam,
is it simply a matter of squaring off the inside ends of the innermost
cores and laminating the wing just exactly as though it were for the
Q2 with the shear web etc just as per plan. This was obviously built
to take landing loads and begs the question that if now not doing so,
it could be / should be laid up with less cloth saving unnecessary
weight ?

Any thoughts and advice greatly appreciated

Regards

Trevor

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