DR-1 (Sands): Builders Group - Page 107

gipsymoth236k · 21 February 2006, 11:34 AM

Jim,

I thought I should include more information about Dr.I airfoils:

F.I and standard Dr.I airfoils had a cord of 800mm, with an axle C/L of 260mm aft of L/E, and 540mm from there aft to T/E. This is very important to know today, as many replica Dr.Is are being built with an incorrect axle C/L dimension of 240mm, which puts the resulting 560mm T/E dimension farther into harm's way with ground contact!

Due to experience with such field damage, later Dr.Is were modified with a shorter cord of 670mm, with an axle C/L of 225mm aft of L/E, and 445mm from there aft to T/E.

These details are clearly reflected in photos on pages 54, 78, and 106 of Alex Imrie's most excellent book, "THE FOKKER TRIPLANE."

I'm surprised that the model companies, as well as the most recent Triplane drawings seem not aware of such small, but important Dr.I details!

Regards, Gary

Jim Bruton · 21 February 2006, 12:51 PM

thanks Gary, guess i'd better get those 30" tyres after all.

gipsymoth236k · 21 February 2006, 02:33 PM

Jim,

As you probably already know, standard Fokker Triplane tires were 710 x 85mm, which is about 28" in diameter.

Regards, Gary

Jim Bruton · 21 February 2006, 02:58 PM

i know! i was just teasing you, in light of your observation of modern day close-to-ground tolerances of the subwing.

gipsymoth236k · 21 February 2006, 10:02 PM

As previously posted, here is a good example of a short-cord, 670mm landing gear airfoil on Dr.I 581/17, as compared to two photos of 103/17's 800mm cord:

Regards, Gary

gipsymoth236k · 21 February 2006, 10:20 PM

Here are two more, both from the front view clearly showing the 800mm long-cord airfoil of 163/17 as compared to the 670mm short-cord airfoil of 525/17 pictured on the right:

Regards, Gary

Jim Bruton · 22 February 2006, 05:37 AM

Hi Gary,

You really can see the difference in the chords of the 2 styles of subwings- I had not noticed it before.

Thank You!

Jim

franzkait · 22 February 2006, 04:20 PM

this is a 160 mm drum, for your Dr1 a 150 or 140mm is OK

Jim Bruton · 22 February 2006, 06:15 PM

Franzkait, the hub looks good- this would allow someone to have a drum brake up inside the hub, rather than a more visible disk type brake. do you have a photo of this type of hub rigged up with the braking system? also, if you can email me a price range, that would be great!

jim

RFC Pilot · 22 February 2006, 07:12 PM

Just off the top of my head, our plane has a front and back section, that butts together around the box.

There are two strips that then screw down over the top and bottom seams, to join them together.

Then there are two thinner straps that run front to rear, on the right and left edges, to assist in holding the two pieces together.