This project does not have an official plan or design anywhere but in my head. By now if you've read my projects in the past then most of this is common sense stuff just adjusting components, scale and general design for different flight characteristics.
Because this is a tow plane I already decided I did not want to tow from the wing as a mounting tow point. Instead I opted to line the inside of the fuselage with 1.5MM balsa to re-enforce it. Then I used 1CM square balsa to add support braces.
The tail recesses into the tail fuselage section so control lines are as flat as possible.
Now all the fuselage components are installed.
Now for towing I installed a plywood mast post which is recessed into the support frame of the fuselage. This will transfer all the towing load to the fuselage through the wing and not the wing itself :)
To give the tail more strength even though as a finished box shape its pretty tough I added some block ribs. Through these I ran the control lines for the least flex and maximum input torque to the control surfaces (lines being allowed to bend take away from the amount the "flap" moves).
I 100% love the Armin wing, so simple to make. This one has a 70CM wingspan with no carbon fibre support as it's not really required and only adds more weight. For more info on the armin wing google or use the search box above.
The stock weight of the model AUW (All Up Weight) is 189 grams (yes lipo battery in there).
Clear view of all installed components minus the tail servos which are now hidden under the box frame structure of the tail.
The 2nd part of this project I wanted to try out was water take off / landings. I created some floats using images from RCGroups (thanks) to design basic shape and dimensions to go from.
My floats however failed, as you can see in this photo the model did actually float and was able to taxi around on the water just fine.
Another image as evidence it did actually go out on the water lol.
Not such a clear image but out of what images turned out its the best. You can see how I've built up speed and was almost up on the step but as it did the floaters kept digging in on the front and almost made it nose down completely. As the primary purpose of the model is towing the floaters failing is not the end of the world, it was fun to try and I will again but for now I accept my design failed.
So I took of the water floaters and added proper wheels to the wings as far out as I dared on the wing, the reason for doing this is the same as cars - increase the wheel base and you increase stability.
But again they failed as on our field there just too small. So while at the club I measured everyone's wheels who where having no issues taking off and landing while others kept nosing over and such. The best size was 10CM so why "re-invent the wheel" (hehe), I took the foam off the stock wheels and used 3 layers of 6MM depron to make 10CM diameter wheels.
This was then UHU Por glues to the hub because the glue has a rubber compound which helps reduce shock load being transferred to the frame. To finish them off and give a little traction I put some elastic bands on again using UHU Por.
You can see I've also changed out the motor. The original did actually tow an Eflite ask-21 glider several times but the power was low, this one has more kick lol. These wheels work excellent on grass and just about anywhere and because the model can fly SO slow perfectly in control you can land almost like a helicopter anyway. So for where it matters (taking off) its golden now :)