Bowman Models Sunduster

[Tom Thomas]

bought this second hand, the right wing was already part built.

Copyright 1972 on the plans so another oldie.

I may modify the bulbous nose because A it will look better and B with electric motors these days the room isn't needed, or is that disrespectful to the original?

A few pics.

Below is the entirety of the build instructions, brief much?

Edited By Tom Thomas 2 on 08/09/2017 02:51:28

[Ian Moody]

I have built and flown a couple of these in the early eighties Tom and can fully recommend it. I once caught a thermal and ended up in the air for about an hour and a half, It floats on and on. Not sure how the weight of lipo will affect it. Looks great with translucent film covering as well and is a dead simple build. Enjoy.

Ian

[Tom Thomas]

What do you think about my idea of streamlining the nose Ian? I just don't like the bulbous look it has!

[Ian Moody]

With an electric motor that would be no problem Tom. I think the reason for the bulbous sides at the front was to maybe hide the cylinder head of the engine more than anything else. It would look sleeker if you narrowed it down a bit. It will be interesting to see it like that. I now live in the North of the UK and we don't get the sort of light winds here for a Sunduster unfortunately.

[Nigel Dell]

Hi Tom

Back in the day I think a lot of us modified kits and plans to suit our needs and make things a little individual, so I think any mods you may do would not be seen as disrespectful just what would have happened back then, you are not changing the core part of the model but bringing into the 21st century with electric power so enhancing the design not detracting from it.

Was a good design in the day just build as you wish and enjoy!

[Tom Thomas]

Well I couldn't have put it better myself Nigel ( no really..... I couldn't)

That's a great way of thinking about it, thanks!

[Tom Thomas]

I need some help please

I've built many models but the tips of the wings have always been a sanded to shape block.

the plans here ask for 1/4 inch sheet.

Now in the pics below you'll see that the ribs have quite an under camber, I'm confused at the 1/4 inch sheet? If that's the width of the tip then how thick is the sheet? It can't mean 1/4 inch thick sheet!

And how do I apply this tip? If it's indeed sheet do I bend it to follow the camber of the rib? Do put it at the top of the rib and follow the contour? In the centre and follow the contour?

Or find a 1/4 inch square piece and sand it to the shape?

I've built lots of models but this has me stumped, have a look at the pics and please explain the simple obvious that I just can't see!

By the way, are those digital caliper things easy to read? Because I'm going to get one, I'm fed up with being unsure of the gauge of balsa I'm using on models with vague instructions.

That's wider than a quarter isn't it?

Below is the camber 

Edited By Tom Thomas 2 on 10/09/2017 03:00:38

[John Emms 1]

The model was designed for the 7.5PG class, that is 7.5cc of fuel in a powered glider from memory.

I built one from the kit, and was surprised that the ribs were a LOT more undercambered than shown on the plan. I am sure it would have flown a lot better with the planned undercamber - or with more power than the worn out DC Merlin. So if anyone found a yellow one in the club room at RAF St Athan in the very early 80s, it was the one I left behind.

On the digital calipers, I would avoid the very cheapest. I use a Draper Expert at work (a Christmas present), which I can rely on being accurate to about 0.03mm. The Draper Expert is kind of okay as a guide for marking at work, but will get lots of use at home in my model tool box, for which it is overkill. The scale on the Draper is easy to read, and the batteries are a common type.

[Ray Dunn]

Hi Tom

That Sunduster wing tip will be quarter inch sheet vertically applied. You posted at 3am UK time. Hopefully things are a bit clearer this morning.

I bought my Sunduster for the club 7.5cc duration competition back around 1980 (it was quite successful, from checking the trophies) a real lightweight floater. With my interest moving towards gliders, I used it a lot for its convenient powered launch method. A few years back, I recovered the wings with lightweight tissue and converted to electric power. (After an experimental single channel model conversation!). Great memories of my test flight immediately hit a good thermal.☺

I'd go with slimming that front end. That high front was a real problem, on a gusty day wing tip landing, the wings twisted had nowhere to go and made a real mess of the fuselage. Or perhaps I was just using too many elastic bands😞 It gained quite a bit of weight during the repairs.

The kit was still for sale recently, which amazed me. Though now showing only as out of stock.

I hope yours flies as well as mine did.

Ray

[Engine Doctor]

1/4 inch sheet looks right to me ? Just cut a rib shape from softish 1/4 sheet and sand to fit . Perhaps it's the early hours tricking you . A rest , a cup of tea or something stronger  and all will be clear .

Edited By Engine Doctor on 10/09/2017 10:21:45

[John Emms 1]

I made a control line speed type cowl for mine out of soft balsa block (with a small air intake in front of the cooling fins).

[Tom Thomas]

Would you would you chaps be implying I may have had a tipple?

Ok maybe I had a small one I get it now thanks chaps! A senior moment me thinks

[Tom Thomas]

Many thanks for the advice and personal experiences of this glider

Cracking on with the horizontal stab tonight.

[Tom Thomas]

Horizontal stab finished! I even managed to put the wingtips on!

[Tom Thomas]

Fues started tonight, longerons, wing seat ( which I have made with 3/16 rather than the stated 1/16) for strength and I have trimmed a bit from the nose section.

I've had to shift the front down a little on the plan because the stab incidence was off, doesn't matter as the rest will come together fine.

The section I removed from the nose.

Edited By Tom Thomas 2 on 13/09/2017 03:09:47

[Tom Thomas]

The manual says to add the doublers, no where on the plan can I see where the doublers are defined, so I took the liberty of adding my own.

in another pic you can see just how much I've taken off the nose,

Adjusting formers etc to fit the new nose is actually quite easy.

Been enjoying it so far.

[Tom Thomas]

Had to double up on 1/8 longerons at the points where the rear formers sit as they were well out!

I'm also going to reduce the width of the wing seat area of the fues as I dry fitted the sides together and I would need to weld the things together to get the nose sides to meet as per plan, don't need the room anyway.

[PatMc]

Hi Tom, I didn't recognise the Sunduster when you asked advice in the Amigo thread. I thought you were converting a pure glider to electric power, that's why I asked for details of size etc.
When I saw this thread I twigged what it was, in fact I once taught a friend to fly the non-powered version [Simpleton] as a slope soarer.

Here's the Bowman ad from an old RM mag.

You were asking about a suitable power combo - I reckon a motor about 50 - 60g weight, a 15 - 25A esc up to about 1200kv & 800 - 1200mAh 3s lipo [lipo size dependant on available room in the model & cg]. This should give about the power of a good 1cc diesel of old, a little more than the DC Merlin shown on the plan.

I like Keda motors and I'm fitting a slighty longer version of this motor in the Amigo which think it would probably suit the Sunduster.
For a model like this I'd usually get Turnigy Plush 25A or Hobbywing FunFly 25A from HK.
I prefer Zippy or Turnigy brand lipos [excluding Turnigy Nano tech] also from HK.

Please bear in mind that I've given my own preferences, there are plenty of other equally suitable choices.

BTW, your build is looking great but if I were you I'd get the power bits together & draw them up on the plan before doing much more on the fuselage.

[Tom Thomas]

Wow, that's just the advice I was after, cheers pat

You couldn't have been more clear, very much appreciated mate

[Tom Thomas]

Well, on you're advice pat I've looked up the motor and its 32mm long, so, I've glued F1 in with 40mm clearance to the nose to give a little room for manoeuvre.

I've got 100mm room behind for the lipo, is that enough do you think?

I've slimmed the fues sides down at the wing seat area also.

[PatMc]

Hi Tom, 100mm should be enough for the lipo but remember the ESC also needs to be accomodated & allow some space for the connectors. I've made a false floor for the battery in the Amigo with the ESC housed underneath. The "floor" is from liteply with a number of 20mm or so dia holes drilled in it the ESC is held in place with a velcro strap. It's a system I already use in an OD 2.4mtr glider & a vintage Veron robot.
Also which way round are you going to mount the motor ? If you're using the X mount on a firewall you'll need to leave some space for he exposed but redundant shaft projecting into the battery area. I suggest you fix the firewall with about 2 degrees of downthrust but this can easily be adjusted with washers if necessary. Personaly I wouldn't bother with any sidethrust, I'd just let the model climb with a natural turn so long as it's not too severe.

[Tom Thomas]

Hi pat, I had thought about the false floor, I was planning on mounting it from the front end, but I'll see once I bought the motor, money's tight so I buy a bit at a time.

Thanks again for the advice it's very much needed and appreciated

[PatMc]

Tom, mounting on the firewall leaves more useable space than mounting from the front. Other advantages are that the wires are clear of the rotating case & access is easier if ever required.
The 2.4mtr glider I mentioned earlier was converted from a geared brushed motor to brushless some time ago by hacking off the nose, gluing in a firewall & some ply hard points to take small servo screws for a cowl. Once the motor was mounted the cowl was pretty well built around it from thin ply & balsa block scraps.

Original brushed motor nose.

The nose is now longer but the brushless motor is lighter than the brushed + gearbox.
Model was flown a number of times with no cowl in case any adjustment proved necessary.

Top & bttom of cowl are flush with the fuselage lines, the sides overlap. Paint on cowl & top hatch was a lucky match with the Solarfilm.

[Tom Thomas]

Oh I see, thanks Pat, I've had artf leccys in he past, but of course it comes with all the gubbins fitted and done!

A bit different when you do it yourself isn't it!

[Tom Thomas]

Bit more done, had to put a balsa laminate either side of the fin base, I was sanding something and snapped the damn thing off

Beefed up the rear of fues where the fin is as left as per plan it would have been very weak.