Electric conversion of an old 84in Svenson Britten Norman Islander

[Murat Kece 1]

I have got an old BN Islander and a Lysander from the collection of a deceased club member. I am converting it to electric.. Has anyone got this Svenson  produced mode (Outerzone plan: oz9714)l? It is about 12 pounds.. It has two HP40 glow engines (I will clean and put them out for sale). Reviews suggest that these mores were overpowered and 30 size motors would have been adequate.

 

I estimate a total power of 1000 to 1200 W. I am thinking of using 2 x 4-Max PO-3547-960 out runner motor 960 KV giving about 600W each  on 10x6 prop and  4S LiPo (or alternatively 11 x 8 on 3S).. I think they should be counter-rotating (CW and CCW) As for the battery I am thinking of 4s 5000 mah 460gr.  May I have your views?

 

I asked George from 4 Max for his advice.  

 

 

 

 

It is in a sorry state  -  it seems like it has accumulated a lot of humidity/damp which makes it soft and fragile, also the covering is separating from the balsa.

 

              

 

First task is to remove the engines and strip it naked.. Wish me luck...

[Andy Gates]

I would wait to assess your power requirements when you have the bare airframe weight known.

 

Personally I do not bother with opposing rotation propellers as I have never found the need.

If the model is flown with respect (i.e. no 0-100% snap throttle movements) then opposing props are not needed.

[Eric Robson]

I'm with Andy, all of my twin electric planes have the same rotation props. All fly well,  three of them are hand launched and fly off dead straight. Big plus no need to keep two sets of spare props.

[Piers Bowlan]

Great restoration/conversion project Murat, following with interest. 👍

[Murat Kece 1]

Started stripping the beast..  It was covered with water-based glass fiber and painted.. It must have loosened due to the dam and water ingress . All came off fairly easily when pulled. A few dent holes under cover were found.. It has seen a previous repair of he throttle control with the mechanical system replaced by servos installed next to the carburetors. The balsa seemed very flexible.. But with drying over a few day it is getting firmer.. 

 

When stripping the fuselage the tail was very loose and came off. It will require a patch up and repair.

 

I also took the 2 x H40 motors and the fuel system out and cleaned the fuel residues with detergent, acetone and rubbing alcohol. Took the UC fairings off as they will be replaced with new built depron ones. Started drawing the new power system up.

I have not striped the tail and the fin and will try to se them as they are.. 

 

                               

 

 

 

 

 

 

The uncovered plane weighs about 4kgs.. George suggested 3547/800KV with 12 x 6 Prop.. AUW estimate is as follows:

 

 

More later..............................

Edited March 1, 2023 by Murat Kece 1

[leccyflyer]

Hi Murat - given your description of the degradation of the balsa due to damp, you will want to remove the covering from the tail surfaces as well, so that you can examine them for damage and structural integrity and especially the joint between the horizontal stabiliser and the fuselage. It's a large heavy model and you need to be 100% sure that the degradation of the timber hasn't also weakened the joints. It's not worth trying to save a bit of covering on the tail.

[Chris Freeman 3]

Very nice project, I built one in the late 80's from the RCM&E plans and also used HP 40's. It flew very well and was eventually sold. i think that less power than your estimates will be needed as twins are very powerfull. I had a TF DC3 that flew well on only a total of 660 watts and that had a 83inch wingspan and was not light.

[Murat Kece 1]

Thanks for the comments.. Brian I  will recheck the fin and the horizontal stabilizer..

 

The  build is going to be better than I anticipated.. It all seems to go smoothly.. The balsa dried and looks in good shape too. While waiting for the delivery of the motors and ESCs, I started with the motor mounts/firewalls and then the missing lower cowls.

I sketched the motor installation on the exiting plan.

 

I tried and tested with a 3547/960 motor that I have..

 

 

 

Using the existing IC motor mounting rails, top of which is the motor centre line,  I built the new firewall and is supports (the lower/bottom support will be added later).  

 

 

I tried the motor and ESC giving a perfect alignment, plenty of room and easy access.. 

 

 

Th I built a jig to make the lower cowling.  I covered it with doculam to prevent any accidental gluing.  I then laminated 2 x 1 mm balsa with epoxy glue. Cut and shaped the cowl intake and epoxy glued it.

 

 

 

 

I am satisfied with the 2 x 1mm laminations even though the plan says 3 x 1.5 mm .. The rigidity seems adequate. It is not load bearing.   

 

 

I am pleased with the days work.. The clearances worked perfectly. Now I need to add the air intake and repeat the process for the port motor.

 

 

 

To be continued....

[PeterF]

I am following on here, I have the plans from RCME now available through Sarik for a design by R Norris which looks very similar to this which I am thinking of building and converting the design to electric. I have all the stuff that was in a Topflite DC-3 and I am looking for something a little less "on the edge" when it comes to flying. As with a previous poster I used to fly my DC-3 on around 800W total for 2 motors, 3S, 970kV motors with 12x6 props running at around 8,500rpm and drawing 37A each. My DC-3 was a bit too heavy at 12lbs, which is what made it a little hairy to fly at times.

 

Have you thought about battery placement yet, are you going to cut a hatch into the fuselage.

[Murat Kece 1]

Hi Peter

Go for it. It is a builders plane.. And I like the looks of it. This will be my first twin engine model.

Mine will be over 12 lb. I could have done with a smaller motor nut I bought them already.. A bit of extra power is good at times.

 

There is ample space for the battery. I ill see how the CG comes up. I think i will just lay it at the bottom of the fus. I do not intend to cut a hatch to maintain the hull rigidity for the impacts from the front U/C... I will use the wing seat opening .. I will  need to unbolt it for battery change out.

 

 

[Murat Kece 1]

Completed the building of the second nacelle for the port motor. This time I used 2mm balsa on its own. I soaked it with water spiked with 5% Ammonia. It worked a treat. I then wrap it around the jig with a few elastic bands and let it dry. Bingo -  It was much easier than laminating..

 

 

I also started cutting some access holes on the bottom of the wings for wiring..

To be continued...

Edited March 3, 2023 by Murat Kece 1

[Murat Kece 1]

 

 

Both 4Max 3547 800kv motors are installed for trial. The wiring is completed with the ESCs in nacelles. The wing holes were plugged back and te servo functions were tested.

 

Used Freddy's Sauce (great stuff)  to smooth out some areas and the nacelle joints.

 

 

 

[Tosh McCaber]

Well done Murat- It's really taking shape.  Looking forward to seeing it fly at the field!

[Murat Kece 1]

I am planning to cover it with Hobbyking covering without any fibre-glassing of the wing or the fuse. Any views on this will be appreciated?

 

[2.4g Shaun]

I have found the Hobby King covering excellent. I've even used it on a 1/3rd scale cub. I buy mine from 4-Max, I'm assuming they buy it from the same factory as HK as it appears identical and I've used both. Bargain price, next day delivery and someone you can talk to on a phone.

Looking forward to the test flight video.

Edited March 16, 2023 by 2.4g Shaun

[2.4g Shaun]

Forgot to mention,

it's only £22.50 for 5 metres for solid colours.

[john stones 1 - Moderator]

H.K films superb, same stuff via 4 Max and Rapid RC I reckon.

[leccyflyer]

Agree 100% with how good the HK film is - a real pleasure to use, right up there with Profilm, but at a fraction of the price.

[Murat Kece 1]

Thanks I got some from 4Max..

[Albert Ace]

On 28/02/2023 at 18:26, Andy Gates said:

I would wait to assess your power requirements when you have the bare airframe weight known.

 

Personally I do not bother with opposing rotation propellers as I have never found the need.

If the model is flown with respect (i.e. no 0-100% snap throttle movements) then opposing props are not needed.

The real one doesn't have opposite rotation props. Nor arfe they needed

[Albert Ace]

On 03/03/2023 at 07:50, PeterF said:

I am following on here, I have the plans from RCME now available through Sarik for a design by R Norris which looks very similar to this which I am thinking of building and converting the design to electric. I have all the stuff that was in a Topflite DC-3 and I am looking for something a little less "on the edge" when it comes to flying. As with a previous poster I used to fly my DC-3 on around 800W total for 2 motors, 3S, 970kV motors with 12x6 props running at around 8,500rpm and drawing 37A each. My DC-3 was a bit too heavy at 12lbs, which is what made it a little hairy to fly at times.

 

Have you thought about battery placement yet, are you going to cut a hatch into the fuselage.

I too have that plan. Somebody in my local club built that model for two I/C motors, didn't last long. A big build, particularly the wing/ Electric is the twin model answer.

Albert Ace

[Murat Kece 1]

 

 

I decided to retain the original livery of Loganair using HK covering materials.. I have some white, red and dark blue.. They should do. 

 

Well continued to clean  and tidy up the wing. I removed the ailerons (chopped the steel retaining pin) and the flaps. Repaired them and covered them with white HK covering. I changed the hinges on the flaps but retained the ones on the ailerons.

 

 

Then I decided to strip the rudder and the elevator as recommended by my friend Leccyflier - I am glad I did they need some TLC too. Then  I noticed that the elevator is a bit skewed to the port side. It was very well epoxied on the the tail.. I took the saw and cut off the elevator and part of the tail. I raised one side and checked against the wing. I left its reinstallation until after the fuselage is covered. 

 

I also removed the front steerable u/c. The retaining /steering collar will need a replacement. The nose needs strengthening. I will make te access hatch removal as its removal was problematic.

 

-----------t be continued.

 

 

 

[David Ovenden]

Great job Murat. It will be a fine model again when you've finished the rebuild. So nice to see an "old" model given a new lease of life. 

 

 

 

 

 

 

 

 

 

 

 

 

[PeterF]

Get the battery(s) well up front and hopefully you will not need all that lead.

[Murat Kece 1]

That is the plan..