Hi electro fans,

after reading a discussion in the waterplane forum about schneider trophy racers: https://www.rcgroups.com/forums/showthread.php?t=419315
I deceided to ask Jim Young if he would allow me to build from his plan, but in 1/7 scale instead 1/8, as the plan is drawed for.
I chose to build the floats first, and milled them at my parents home. Man, are they slim!
Here are some pics from the beginning.

Kuni

Hi Kuni,

Looking good so far. For the floats, I was planning on cutting sections of 4" foam and then shaping before planking. I'll keep an eye on how yours come out before I make a final decission. I probably won't start building 'til December. I'll start on something else so we can learn from each other's mistakes.

I've been working on the plans, and made a few updates. I'm still struggling with the elevator, and have two shapes drawn. Let me know whick one you like. Also, I think I've worked out a good way to do the landing gear struts. I'll send a new DXF file.

-Jim

Jim,

have downloaded your plan update. Looks good so far, but I just can't judge about the stability of the strut-in-foam solution. I have never worked with foam. The elevator shape is a bit less rounded, hmm? Ribs look good, but you know I will build with a tube spar. No problem at all, I draw my own.
Do you plan to add washout to the wings?

I worked a bit on the float today, adding the side-longerons. It looks more like a float now. Jim, I had to crack the second float former and insert a small (2mm wide) triangle just behind the longeron for a proper smooth curve. Maybe it is my inserted former who will hold the front strut in place, but I feel there is a mistake in the bottom edge curve. The others fit fine.
Maybe we will have a problem to get the right prop spinners later, because the S65 had at the rear prop a very long, straight spinner. Anyone has an idea?
Okay, That's it so far.
Here are the pics.

Kuni

Hi Kuni,

I'm pretty confident in the strut in foam. I plan to use Gorilla Glue, and that foams us to fill in voids so I think it will be plenty solid. The elevator shape is less rounded, and I don't like it as much as the original drawing. However, I think it is more scale according to the photos. It is your choice. I'll take a look at the float formers, this is good feedback to make a viable plan. Keep it coming.

I don't think any washout is needed, but you could add in a bit. Just slide the trailing edge jig forward a bit at the tip. To hold the trailing edge up off the board, I put in a 1/8" strip on the plans as shown by a pair of dotted lines. This will put the main spar flat on the board. After you sheet the top of the wing and flip it over, use a 1/2" strip to keep the wing flat while you sheet the bottom. You may need to move these a bit forward for your larger scale plan. I'm planning on a fully sheeted wing (1/16" balsa).

I'd like to see your tube spar construction (no comments from the peanut galery). What size do you plan on using? how many? I found a local kite shop that deals with all kinds of sizes, shapes, and strengths of carbon tubes and rods.

-Jim

P.S. How are you going to fix the struts into the brass tubes you sewed to the formers?

-Jim

Hi Jim,

I plan to hold the wires in place with working rigging cables from nylon covered steel wire. The struts will get a stopping point soldered to them, than slide into the brass tubes (I still have to mount the front one), and attached the wires to the floats and bottom of fuse. This arrangement can flex only a little bit, and should be stiff enough to hold the floats in place.
Maybe the Savoia engineers worked some time on the elevator shape; I have a pic that shows the rounded shape you drawed first. I would use it also.

For the main spar I want to use a single 10mm carbon tube, shear web and fully sheeted wing. I built a wing some years ago with this method (for a trimaran sailing boat) and it lives! Plenty strong and instantly built-in joint.
But I will use working rigging cables again. They can hold the whole plane together, without the need of anything else to do this job. Screws only for the struts and middle wing-to-fuse-joint.

Kuni

Hi,
worked on the formers again. I had to double some balsa strips onto former 2,3,4 and 5. Pictures show this well. Now the float seems to have a smooth curve at all angles, if one plank strip is used. The max. thickness of the strip is 1,2mm, so it may be marginal, but I wanted prevent the look of a hollow deck, if fully planked.
Next I will plank the whole rounded deck area, than paint the inner side, plank again the bottom, and remove from the building board. Than the foot-parts can be removed, paint the rest and plank the middle deck. Float finished!

The pictures show the first plank and the nose block for a better shape.

Jim, do you have photos of this bird that are not shown in the schneider thread?

Kuni

Hi Kuni,

Most of my photos I got off of the model link you posted in the Schneider Trophy thread. You are welcome to what I have colected so far, 55 photos and drawings (14MB). Let me kow if you want me to send it and how much you can accept in an email. The other option is to start posting them here.

-Jim

Jim,
I only wanted some more pictures for later detailing. Posting them here will be okay; I can download what I need from here.
The attachment points on the floats seem to be inside the hull, hmm? Nothing to see except the wire. I will have to attach the wires to somthing glued to the formers, for stiffness.

Kuni

Kuni,

You are Awesome! First the S-55, now this -65. Looking forward to your pictures.

Terry

Hi Kuni,

If you look closely at the photo of the guys wheeling it out of the shop, you can see a faint hint of a flying wire between the front struts. In two photos I got from Martin, it shows a flying wire attached basically at the base of each of the struts. What I'm thinking is since the struts will be music wire with some wood or carbon wrapped around them, you could hide the attachment point under this. In the front shot, you can't see any flying wires between the float, but also notice that there is only one strut going up to the tail booms. This must be an early photo, and later they added the addition strut and more bracing.

-Jim

Terry,
thank you for the kind words, but I don't think it is awesome. For me it seems to be the logical next step. I could learn much about contra-rotating prop-systems while trying with the S55. I built a coaxial motor, that will drive a MC72 some day. The S65 is nearly a S55, but more streamelined. The wing is easier too, as should be the flying habits. With the same power she should be much faster.

Jim,
the inside and inter-strut wires are not my concern. What I mean is the attachment of the wires going from the floats to the wings. They will pick up much flying loads, and have to be attached careful to the floats. I thought about gluing some aluminium part to the ply formers, that also hold the brass tubes. But always there will be a part looking out of the hull. Maybe some small eyebolts, glued permanent to the ply formers?

Here is what I did today: the fully planked float deck.

Kuni

Hi Kuni,

I would keep the stress off of the floats, and attach any flying wires to the struts just above where they insert into the floats. You said you were going to have a stop on the struts anyways. Just make this a tab you can attach the flying wires to. Just a suggestion.

-Jim

Jim,
you are right in all facts, but when I look at the front view, there would be a big difference between the original attachment point and the one on the float strut. I am worried it will not look right, when finished.
I will make a test with selfmade eyebolts.

Kuni

Just don't pu the front view in your documentation package!