Comment

Comment by Ron D Leclerc on April 27, 2012 at 10:14am

G'Day champ...

 

Are you using metric thickness for the PC?   I checked for what is available here and I can get 1/8"(3.3mm), 0.093"(2.4mm) or 0,08"(2.0mm).  I would use the 1/8" for both thr roof and windshield... I was also thinking of a butt joint!   The thiness PC is  0.06"(1.6mm)... I would use for the doors!

 

They use 1/8" for the 750 roof and there is no spec for the 701 roof!!!

Ron

 

Comment by Chumphol Sirinavin on April 27, 2012 at 1:01am

My second thought is butt joint will be better without the bulging of the overlapped edges and you don't have to look for rivets with long grip. I will try 3 butt joints with 2 mm. scrap pieces, using hot glue, epoxy and dichloromethane.

A friend suggested (rather late for me) that 3 mm is much more stronger for windshield.

Champ

Comment by Ron D Leclerc on April 25, 2012 at 10:46am

Hey champ...

 

Just looking at your beany mod... and what do you do with the joint between the windshield and new roof, is that a butt joint or is the windshield overlaping the new roof/  How thick is  the new roof... I checked out my drawings and Zenith did NOT indicate a material thickness.  Just the door(0.04) and window(1/8")!

Ron

Comment by Chumphol Sirinavin on April 23, 2012 at 12:55am

For CH 701 roof mod without the diagonal tube, see my comment on Sebastien's blog New CH 750 Features.. My first CH 701 roof will remain with the bent up diagonal tube as shown above.

Comment by Paul Saccani on April 22, 2012 at 10:08pm

With regard to an air balance tube between the wings.  This strikes me as a useless exercise, which under some cases (like unbalanced flight), could cause loss of fuel via flow from a high side tank to a full low side tank and overflow.

Varying fuel flow from tank to tank would have much more signicant elements (fuel level, hose routing, unbalanced flight, vapour locks) than ram air pressure differences, so I would suggest that it would just be weight put to no good purpose.

Comment by Chumphol Sirinavin on April 22, 2012 at 9:57am

Hi Paul,

Please see my comments on Sebastien's blog New STOL CH 750 features introduced at Sun'n Fun and look at my pictures there for my cabin roof frame mod.

Actually, I used 2mm polycarbonate and I do not think the curved up roof will ever cave in. Now, If you use 3mm, you will have a very strong roof with no tubes or angles to obstruct your view through the roof, like the 3rd edition 750.

Best,

Champ

Comment by Chumphol Sirinavin on April 22, 2012 at 3:44am

Paul,
My internet connection is rather erratic today. I could not attach pictures for you. I will have to try with a direct email later.

Dave,
Just imagine that each of your wing tank has two outlets, one at the front and one at the rear. one of them or both will keep fuel supply to the engine, the front one at nose low attitude and the rear at nose high attitude. If you have fuel hoses from both wings connected at a common low point, one of the wing tanks if not both will keep fuel flowing. For unbalanced fuel between the two wings, a T-connector at each wing root before going through a valve will give you choice to use fuel from which wing or from both. The balance tube you mention might work, but I need some time to think it over for all flight attitudes possible.

Best,
Champ

Comment by david shrader on April 22, 2012 at 3:01am

I love it champ. I keep thinking there has to be a way to incorporate a balance tube for tank venting now that the wing profile is carried thru over the cabin. Looking at your pics it appears the beanie mod. almost allows enough room (height) to keep a balance tube from being a low spot. I know your tanks are wet but if they were standard could a tank vent balance line make it straight across from L/H tank to R/H tank without having to drop down at the cabin? I've read that fuel flow rate is different between wings (fuel imbalance) because there is a slight difference in ram air pressure between L/H & R/H tanks, the easiest solution would be to install a balance tube between them if there isn't a low spot where fuel could block the line.
Dave

Comment by Paul Saccani on April 22, 2012 at 1:12am

Yep, plenty smart.  I was thinking of just drilling new hole where the windscreen contacted to the tube, but it is much smarter to spread the stress with an L angle.  Perhaps a 2 or 3 cm strip of 20 thou between the windshield and tube, at a tangent to the contact point might serve as well for stress relief, for less weight?

When I do a major overhaul next, I think I will be making a new 7F18-1SP (cabin frame) and deleting 7F12-2 (cross tube).  On 7F18-1SP, I would delete the diagonal tube and entry handles and extend the 4130 upper tubes to 250, with a diagonal tube of 3/4" 4130 from 200 to 200 from the corner of the upper tubes and the centre tube of the cabin frame on each side.  Much like the 3rd edition 750, needless to say..

I have a stupid question - on the wing, the ribs do not act in isolation, so the upwards force on the skin does not tend to pull them towards the sking.  On this one, the cabin root ribs seem to have a fair bending moment on their attachement to the upper tubes of the cabin.  Is the curve of the 3mm PC over the ribs going to provide enough strength to stop those ribs bending inwards?  Polycarbonate is a good deal more flexible than aluminium, but on the other hand, that is quite a thickness.  Please forgive the curiosity.

Regards,

Paul.

Comment by Chumphol Sirinavin on April 20, 2012 at 8:57pm

G'Day Paul,

If without this inverted L angle, the upper corners of the windshield will be more stressed with a smaller radius of turn.

Have a nice day.

Champ

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