Cobra 3520/14 Nose Mount

[Ken Culbertson]

I am having a real hard time designing a proper front motor mount for a full body fuselage around my Cobra 3520/14.  I have some of Tom Morris's nose rings which should work fine on a profile but I don't see how to use them for a full body.  I also need a recommendation for a collet prop adapter.  The set screw ones I have are too short to reach the set screw position.  I have scoured the site for some pictures but all I could find were ones for a molded CF front mount.  Again, why am I better off using a front mount?

Ken

[Crist Rigotti]

I am having a real hard time designing a proper front motor mount for a full body fuselage around my Cobra 3520/14.  I have some of Tom Morris's nose rings which should work fine on a profile but I don't see how to use them for a full body.  I also need a recommendation for a collet prop adapter.  The set screw ones I have are too short to reach the set screw position.  I have scoured the site for some pictures but all I could find were ones for a molded CF front mount.  Again, why am I better off using a front mount?

Ken

Search my build logs over in the electric section.  You'll find all your answers there.

[John Rist]

I recommend  the Motor mount by Bob Hunt (G-10 hard noise).  Robin's View Productions in the vendor's section.  I have used several.  They provide a solid mount.

https://stunthanger.com/smf/robin's-view-productions/new-product-hardnose-electric-front-mount/

[Ken Culbertson]

I recommend  the Motor mount by Bob Hunt (G-10 hard noise).  Robin's View Productions in the vendor's section.  I have used several.  They provide a solid mount.

https://stunthanger.com/smf/robin's-view-productions/new-product-hardnose-electric-front-mount/

The mount looks great, I will probably order one but what I am looking for is the overall nose design.  With a front mount I just don't see how you get a solid mount.  The only pictures I have been able to find so far are either profiles or rear mounts.

Ken

[Ken Culbertson]

Search my build logs over in the electric section.  You'll find all your answers there.

Crist:
I have been unable to find what you are pointing to.  There is nothing in your anchored thread about front mounts.  I am probably looking in the wrong place.

Ken

[John McFayden]

Bob Hunt will send you a detailed pdf explaining how to solidly install the mount he sells. Just ask him to email it to you.

[Crist Rigotti]

Crist:
I have been unable to find what you are pointing to.  There is nothing in your anchored thread about front mounts.  I am probably looking in the wrong place.

Ken

Start with Reply #89
https://stunthanger.com/smf/gettin-all-amp'ed-up!/2016-electric-stunter-build-log/50/

[Fred Underwood]

Crist,
You need a new build thread.  I enjoyed those.

[Ken Culbertson]

Start with Reply #89
https://stunthanger.com/smf/gettin-all-amp'ed-up!/2016-electric-stunter-build-log/50/

Thanks Crist, that was exactly what I needed to get the design juices flowing.  Since I have never done a front mount electric I had no clue if simply building a reinforced shell around the mount would work.  If that plane flew then it did!  I hope you picked the Thunderbird finish.  My favorite too.

Ken

[Crist Rigotti]

Thanks Crist, that was exactly what I needed to get the design juices flowing.  Since I have never done a front mount electric I had no clue if simply building a reinforced shell around the mount would work.  If that plane flew then it did!  I hope you picked the Thunderbird finish.  My favorite too.

Ken

You're welcome Ken.
Read on on what I decided on the paint scheme.

[Ken Culbertson]

You're welcome Ken.
Read on on what I decided on the paint scheme.

I will forgive you.  It really did turn out beautiful.  I do have a couple of follow up questions. First, how has the top hatch worked out?  I am seriously considering using one.  Most everybody uses bottom.  Mike puts his on the side.  I sort of like the top.  Second the engine offset.  My first e-flights were with my twister that I am using to make all of the rookie mistakes.  Engine thrust line changes seemed to have a more positive impact than they did on IC.  Am I imagining that?  If so then we need to start thinking about "Macro" trim flights before putting on the final finish.  I just hate it when the spinner doesn't fit.  With a rear mount you can build an adjustable cowling but I don't see how with front mount.  At least they don't distort as much as IC.  Lastly, how is the plane today?

Ken

[Howard Rush]

Again, why am I better off using a front mount?

I use a rear mount.  That said, from what I've seen of Cobras, the bearings tend to go bad sooner when they are rear mounted.  I think you did the right thing by front mounting it.

[Tim Wescott]

Again, why am I better off using a front mount?

The location of the bearings in the motor puts them closer to the prop when you use a front mount.  Which is probably why people have observed motors working longer with front mounts.  Speaking just as someone who's watched from afar, it does seem to vary by brand -- I'd use front mount if I switched to electric, though.

[Crist Rigotti]

I will forgive you.  It really did turn out beautiful.  I do have a couple of follow up questions. First, how has the top hatch worked out?  I am seriously considering using one.  Most everybody uses bottom.  Mike puts his on the side.  I sort of like the top.  Second the engine offset.  My first e-flights were with my twister that I am using to make all of the rookie mistakes.  Engine thrust line changes seemed to have a more positive impact than they did on IC.  Am I imagining that?  If so then we need to start thinking about "Macro" trim flights before putting on the final finish.  I just hate it when the spinner doesn't fit.  With a rear mount you can build an adjustable cowling but I don't see how with front mount.  At least they don't distort as much as IC.  Lastly, how is the plane today?

Ken

Thanks for the forgiveness.  Than you, it did turn out nice.
When I make another one, it'll have a side hatch like Mike's.
I have always liked 2 degrees of out thrust. My ECL uses a pusher configuration so about 2 degrees of up thrust was used.
The plane was used in the Labor day contest at Hobby park and flew well.

[Howard Rush]

The location of the bearings in the motor puts them closer to the prop when you use a front mount.  Which is probably why people have observed motors working longer with front mounts. 

My observation, equally as limited as that for Cobras, is that E-flites work better rear mounted. I suspect resonances in both cases.

[Ken Culbertson]

Thanks for the forgiveness.  Than you, it did turn out nice.
When I make another one, it'll have a side hatch like Mike's.
I have always liked 2 degrees of out thrust. My ECL uses a pusher configuration so about 2 degrees of up thrust was used.
The plane was used in the Labor day contest at Hobby park and flew well.

What I love about this hobby is that no matter how long you have been doing it and how much you think you know there is always more.  I totally see the benefit of the front mount but I hate the fat nose it produces.  The molded fiber fuselages solve that but with balsa it is difficult to get that smooth taper into the spinner.  Your build has given me the ideas I need to make it work.  I am going to take some pictures of Mike's setup tomorrow.  I love the ease he makes battery swaps and it looks great.  I am fascinated by the upthrust.  I have never paid too much attention to the fuselage angle and I probably should.  I am not after a 20 pointer and will most likely MonoKote the wings so a trim flight or 2 before finishing the nose should solve my "blending the spinner" fetish.

Ken

[Vitalis Pilkionis]

This is a Cobra 3520 front mount I designed for my Strega's fuselage. I am going to make it from a fiberglass circuit board plate I bought at the local advertising materials store. Two layers of 3/64 thickness will be used. I retained stock hardwood rails, just had to change their profile for a motor to fit.

Vitalis

[M. Scott]

Remember,  I was telling you about Bob Hunts detailed
Plans, he is a great help. He also follows
Stunt Hanger.. . So he may post a video.
Mike

[Ken Culbertson]

Remember,  I was telling you about Bob Hunts detailed
Plans, he is a great help. He also follows
Stunt Hanger.. . So he may post a video.
Mike

Robin sent the entire set yesterday!

[Dennis Toth]

Ken,
Tom Morris has a complete front mount with side bearers for large and smaller motors. His mount ring is secured to the hardwood beam mounts with screws as well as glue. This is the most secure way of doing front mount as glue alone has been know to fail. I have done something similar on my Stuka using small screws through the plywood doubler to keep the mount ring from twisting and working lose.


Best,   DennisT