That's impressive. I'm looking forward to practising. There was a 108-2 on floats near me with an IO-360 Conti that could get airborne in 11 seconds on 2425s. Do you remember which Fowlers he put on it?

Since I'm going to be running electronic ignition, I don't have mags in the way so I'm going to stuff that O-540 right up tight against the firewall and put a minimum 4" prop extension on it. It may even be possible to put a 6" on there. The C-of-G looks much better when I ran numbers based on those scenarios. I'm determined not to have to carry ballast.

VortexAlternator wrote:That's impressive. I'm looking forward to practising. There was a 108-2 on floats near me with an IO-360 Conti that could get airborne in 11 seconds on 2425s. Do you remember which Fowlers he put on it?

Since I'm going to be running electronic ignition, I don't have mags in the way so I'm going to stuff that O-540 right up tight against the firewall and put a minimum 4" prop extension on it. It may even be possible to put a 6" on there. The C-of-G looks much better when I ran numbers based on those scenarios. I'm determined not to have to carry ballast.

If you can, design a engine mount that can swing out like the super cubs have. Much easier to work on the back side of the engine that way. Especially since you are tucking it so close to the firewall.

A1Skinner wrote:

VortexAlternator wrote:That's impressive. I'm looking forward to practising. There was a 108-2 on floats near me with an IO-360 Conti that could get airborne in 11 seconds on 2425s. Do you remember which Fowlers he put on it?

Since I'm going to be running electronic ignition, I don't have mags in the way so I'm going to stuff that O-540 right up tight against the firewall and put a minimum 4" prop extension on it. It may even be possible to put a 6" on there. The C-of-G looks much better when I ran numbers based on those scenarios. I'm determined not to have to carry ballast.

If you can, design a engine mount that can swing out like the super cubs have. Much easier to work on the back side of the engine that way. Especially since you are tucking it so close to the firewall.

A1 Skinner for the WIN, a fantastic idea

I like the idea and I am considering a swing out mount but there isn’t much to maintain on the back of my engine once the vac pump, fuel pump and mags are removed. When I mock it up and hang the engine where it’s going to live, I’ll have a good think on it. In order to swing it, you have to have extra hose length or disconnect your controls and hoses. It may be possible to mount all the firewall accessories within easy reach without having to swing.

There’s lots of extra planning and fabrication to do it right and make it really functional but when have I ever shied away from overthinking things?

Got some work done on the mount in the last few days.

I made up a pull test jig with a hydraulic cylinder and gauge to get an idea of the strength of my welds. Test is .049 x 7/8" to .065 x 1". This single weld held over 30 times the weight of my motor in straight tension.



This coupon was the first pass and was a bit fast/cold. Sheared the weld instead of the tube.



I slowed down my passes and put a bit more heat in there. I'm used to welding stainless where you want to get in and out as fast as possible.



Penetration was fine on the first pass but I think more heat allowed the 4130 to cool slower resulting in a stronger, less brittle weld. This is counter to what I've heard some people say about welding 4130. Using .045 ER70S2 rod. This pass failed at the tube, not the weld.



Mount to Lord isolator pads...



Ring setup. Experience making tight mitres in wood seems to have paid off. Really happy with this fit!



Some challenges showing themselves in there.



Tig welding in the tight areas was a challenge but some tin foil, a swivel vise, purging and some patience really paid off.



Picked up that vise a few days ago and all I can say is "where have you been all my life" It's been such a great help in getting the welds into position.



All tacked up.

When we did the airframe and motor mount on our Bearhawk we did it with tig and used 309ss filler rod and it worked really well for us.
We cross drilled all the connections. pulled a vacume to remove the moisture the pressurized them with 10 psi of dry nitrogen and two gauges on the dash. You can watch the gauges go up and down with the temp, part of the preflight check. No pressure no fly.

That's a good idea. I purged these with argon before welding them closed. What's the advantage to using 309?

VortexAlternator wrote:Since I'm going to be running electronic ignition, I don't have mags in the way so I'm going to stuff that O-540 right up tight against the firewall and put a minimum 4" prop extension on it. It may even be possible to put a 6" on there. The C-of-G looks much better when I ran numbers based on those scenarios. I'm determined not to have to carry ballast.

I had a similar line of thinking when I built my Bearhawk; a nice CG that would would make the plane handle nicely without ballast. Unfortunately there’s always a trade off and Cessna knew what they were doing. My BH flies great without ballast but it’s impossible to load it to gross weight with people and gear; it exceeds the aft CG limit first. I wish I had used a big heavy engine so I could use my airplane for the intended purpose. But it sure flies nice when light and maybe that’s your mission.

175 magnum wrote:When we did the airframe and motor mount on our Bearhawk we did it with tig and used 309ss filler rod and it worked really well for us.
We cross drilled all the connections. pulled a vacume to remove the moisture the pressurized them with 10 psi of dry nitrogen and two gauges on the dash. You can watch the gauges go up and down with the temp, part of the preflight check. No pressure no fly.

This never crossed my mind but is extremely interesting.

Do people ever do this with fuselages?

I had heard about using 309 and was told it was easy to use and a perfect match for 4130. I check it out with a couple of very experienced welding instructors as well as The Lincoln people and they all said it was a very good choice so we went with it and it worked great for us. The reason to cross drill and pull a vacuum was to remove all the air and moisture then fill it up with nitrogen,. No water or oxygen no rust and the gauges just prove the welds are holding.

175 magnum wrote:When we did the airframe and motor mount on our Bearhawk we did it with tig and used 309ss filler rod and it worked really well for us.
We cross drilled all the connections. pulled a vacume to remove the moisture the pressurized them with 10 psi of dry nitrogen and two gauges on the dash. You can watch the gauges go up and down with the temp, part of the preflight check. No pressure no fly.

I flew a acrobatic Zlin many years ago that had the same feature done with the main wing spar.

I had a similar line of thinking when I built my Bearhawk; a nice CG that would would make the plane handle nicely without ballast. Unfortunately there’s always a trade off and Cessna knew what they were doing. My BH flies great without ballast but it’s impossible to load it to gross weight with people and gear; it exceeds the aft CG limit first. I wish I had used a big heavy engine so I could use my airplane for the intended purpose. But it sure flies nice when light and maybe that’s your mission.

Aft limit is not a problem. I'm trying to keep within the original Stinson C of G which can't be out of aft limit no matter where you put the load in the cabin. The ballast is required in some of the heavier engine installs which put the plane out of limit of the forward C of G.

Update time. Been busy with everything as usual but fit some time in there for the Skook.

I had to let the mount marinate in my brain for a while before continuing. Deciding on the swing out or not situation was finally concluded with a yes. You can see how close to the firewall I’m going but my accessory case has been gradually depopulated to the point where all
I have on there is the Airwolf remote filter adapter. I just made the decision to turf the vacuum system and gauges but I’m considering adding a back up alternator on that pad as I have a dual plasma EFI so electrical redundancy is pretty darn important. Anyway, here’s the mount so far.



A little rotary table work makes for such a nice radius.



Mount hinges are 0.128 4130 and will have a web welded on both sides to box them otherwise that bend radius would be too small by itself.



My notcher is a cheapo unit from Princess Auto that can’t cut shallow angles so I had to set these up on the lathe. Very satisfying to cut compared to a drill and a hole saw.



Some unboxing now… hmmmm. what’s this mysterious metal for the firewall?



What time is it?!? Got have some extra steam to make up for the loss of the AI.



A succulent serving of servo.



And the darn home wrecker breaking up the six pack:



And just because I can, so you may enjoy, a Canso. It was parked at Bounday Bay for some filming. How could I resist?

Looking great!
Man the canso sure looks different painted grey. It's home is a 15 minute flight from me and they've been bugging me to start flying it with them. Come next summer I think I'll have the same conclusion as your post, how could I resist?

I was in Fairview for fuel this Fall. I wondered why the Canso was absent. This is good. The foundation can use the income from the movie job.

That mount is absolutely awesome!!!! Every airplane should have a swing mount, in my opinion!!!
John

Pinecone wrote:I was in Fairview for fuel this Fall. I wondered why the Canso was absent. This is good. The foundation can use the income from the movie job.

Where does she live normally?

VortexAlternator wrote:

Pinecone wrote:I was in Fairview for fuel this Fall. I wondered why the Canso was absent. This is good. The foundation can use the income from the movie job.

Where does she live normally?

She lives in Fairview. A foundation based there got her on flying condition again and a group of guys maintain and fly her. She was repainted for the movie, and as Pinecone said the extra cash flow will be great for keeping her flying for the years to come.

Here she is in her fire fighting livery: https://youtu.be/FHK4beS7eoo

Engine mount is looking great. Now I want a rotary table for those radii.

I feel intuitively that a swing mount has much less internal tension than a one piece, and will be less prone to cracking.