Sealand Project Diary

by Trevor Hewson

As the Winter of 2006 approached I felt the need to undertake a proper building project, especially after having something of an ARTF year (Piper Cub and Mig 3). But what to build? As a browse through my online log books will show, I already have too many models which don’t get enough flying so it would have to be something that would extend the flying opportunities. Remembering the fun of flying the Miss Hyperion off water, the idea of a flying boat of some sort arose. However, we really don’t have a regularly available aquatic site so, if the model was going to see some air time, it would have to be flyable off land too, so I started looking around for amphibious subects.

The need for back-friendly easy rigging at the field ruled out biplanes but, to take full advantage of electric power, a twin engined subject had some attraction. It would be neat to say that my choice of the Sealand was inspired by finding the above poster for sale on eBay. However the reality is that, after a bit of web surfing, I alighted upon the plans of Canadian modeller Ivan Pettigrew and I eventually chose the Sealand from his extensive collection (at ). This model spans just under 75in and Ivan’s prototype flew on 8 CP1700 NiCds at an AUW (without wheels) of 60oz. With a wing area of just under 700 sq ins, this model is very light at a loading of 12.6oz/sq ft. For once then, I could look forward to building a model without looking for opportunities to lighten it at every stage!

Once the plan arrived (Ivan's service was very prompt), I ordered up a selection of wood from FliteHook, cleared some space in the workshop and made a start. Throughout this project, I have reported progress by e-mail, with accompanying pictures, to a few fellow modellers, seeking their advice and discussing various issues as they arose. During this time, one of them (Mike Roach) took over the care and maintenance of the Christchurch and District Model Flying Club website and promptly launched a 'Projects' section where he began posting pictures of the Sealand along with extracts from my e-mail messages. This worked so well that I have shamelessly cribbed the idea for what follows. I have tried to keep each diary entry fairly brief, but you will see several 'More..' links which you can follow for more pictures and/or explanations if you are interested in that stage of construction.

November 2006 (More on November)
The main fuselage framework is built up from 3/16in square balsa sticks. At this stage the model looks alarmingly reminiscent of the Keil Kraft rubber powered models of my youth - I distinctly remember struggling to build an Achilles, which never did fly successfully. Pulling in the lower longerons at the rear step position looked a little alarming but it all worked okay.

At this stage I opted to defer putting the upper bulkheads in place so that the model would sit inverted on the building board whilst I tackled the hull. Although I wanted to follow Ivan’s lightweight construction approach, I must confess that I did add the two X braces you see in the picture below to reduce the risk of distorting or damaging the structure whilst working on it.

December 2006 (More on December)
Building the hull involves persuading some 1/16in sheeting around some interesting contours but the construction has been carefully thought out and it worked out very well. Ivan recommends sheeting the forward underside in either 3/32in balsa or 1/32in ply. I opted for the balsa route but, suffering from a bit of brain fade, just carried on with the 1/16! Rather than strip it off, I decided to glass cloth and epoxy the lower fus on the basis that this would help to resist the water - and any floating debris as well.

Before doing this though I set about the undercarriage arrangements. Having resisted the efforts of various clubmates to talk me into doing full working retracts, I opted instead to make the wheels removeable and keep the option to replace the tailwheel with a water rudder should this prove necessary. Then, with help and advice from Andrew Tubb, I set about the glass cloth and epoxy treatment, which I must admit went rather better than I feared it might. With the undercarriage sorted and the glassing complete, December culminated with a flotation test, just to check that everything was watertight.

January 2007 (More on January)

This seemed a good opportunity to get all the control linkages, servo mountings and hinges sorted out, whilst everything was accessible. No matter how well drawn the plan, there is always an element of making this up as you go along but again, seeing the control surfaces actually move for the first time is a rewarding stage of construction.

Attention now turned to the tail end of the model. As you can see, the tail surfaces are very lightly built. I wanted to route an aerial tube up through the fin which added to the complexity a bit but, as is often the case with these things, once I did manage to get it all fitted together, the end result was rather satisfying.

After sheeting from the fin fairing forward to the wing seat, the fuselage was put aside and work started on the wing.

February 2007 (More on February)

Again, aileron servo, linkages and hinges were sorted out early, before applying the leading edge sheeting. As in the flotation test, my old NiCd batteries were pressed into service as weights.

The string you can see hanging from the front of the wing is for the subsequent routing of the motor wiring.

Rather than building the wing as three separate panels construction starts by building a full span spar. Thereafter, one is faced with working around a wing of just over six feet in length. This called for some re-arrangement of the workshop - and a lot of care to avoid breaking the structure during its early stages of construction.

Once the main wing sheeting was complete, it was time to attend to the nacelles and engine mountings. The motors are Hyperion brushless outrunners. They were chosen to pull between 10 and 15 amps each on a three cell LiPo battery, turning 10 inch propellers. A quick test showed a current draw of 13.5amps on one motor so hopefully, they will be about right.

Being brushless motors, two speed controllers are needed. If these were mounted in the fuselage, there would be six motor wires to connect when the wing was fitted. If mounted in the wing, the speed controllers would be rather inaccessible and not get much in the way of cooling air. Also the battery leads would need extending - not a good idea with brushless motors. Eventually I decided to permanently wire the speed controllers to the motors, but leave them dangling beneath the wing, the idea being to pull them forwards after the wing is installed, so minimising the length of the power leads.

Next, a balance check was carried out, prior to fabricating and mounting a battery box. Then it was a case of hitting the 1/16in sheet again to tackle the wing fairings, nacelle skins, motor cowls, front upper fuselage, top hatch and cabin roof.

Finally, with the addition of a noseblock, the model is really beginning to look the part. About this time I started doing a bit of research into the full size Sealand. Eventually I managed to correlate this with the colour poster illustrated at the top of this page, which I found on eBay. It seems that these were the colours used for the sales promotion tour. Indeed the original poster may itself have been produced as part of this promotion.

Click here for more on researching the full size Sealand.

March 2007 (More on March)

Before tidying up the workshop in preparation for covering, I thought I had better try to get as much of the balsa-bashing as possible out of the way, so started work on the tip floats. These are yet again of 1/16 sheet , over a basic framework.

I also noticed that the full size had a mast on the top of the fuselage behind the cockpit, which would make a useful handle for removing the hatch which, being retained by small magnets, was otherwise only removeable by reaching into the fus and pushing it upwards!

Then there was the issue of a battery box and, before long, I had built up quite a collection of ancillary parts.

After fitting a frosted windshield, I reached the point where the covering could be delayed no more. I don't dislike this task, but it always seems to take a lot longer than I expect. However, the result was worth it and suddenly the model began to look less like an intricate construction project and more like a streamlined flying machine.

Having got the airframe covered, I then set about applying the white pinstripes and added some stickers to simulate the side windows. This transformed the model yet again and, if I look a little self satisfied in this photo (taken on an inspection visit by Mike Roach), then I can only say that this is what makes these projects worthwhile.

Sorry I forgot to fit the tip floats for this picture!

By the end of the month, I had got the wiring done, control surfaces hinged and working and was beginning to get that pre-maiden flight feeling....

April 2007 (More Flight Pictures)

... and it flies!

The model handles extremely well and I can easily get two 15min flights out of one 3700mah 3s LiPo battery. Being so lightly loaded though, it looks best when flown in fairly calm weather.

After a while, I felt that it would be nice to see the model in 'wheels up' mode, so it was a case of waiting for a suitable occasion...

July 2007 (More 'Wheels up' pictures)

After two wet months, I finally got to the flying field on a day when the wind was light and plucked up the courage to fly the model without wheels and with the tip floats. It looked really good and, to my relief, the air was perfectly smooth on the landing approach and the tip floats never even touched the ground.


The only problem now was that, because of the very wide fuselage, I was finding difficulty in recruiting volunteers to hand launch the model, so the wheels went back on for a while. Sooner or later though, something had to be done. . .

October 2007 (Even more 'Wheels up' pictures)

The original undercarriage wires on the Sealand turned out to be a bit thin and 'twangy' so were replaced fairly early on with a heavier guage wire. When I came across the original u/c wires during a tidy-up, the idea occurred of trying a drop off undercart, so that I could fly the model 'wheels-up' without the need for a hand launch.


The picture shows the Mk. II fixed (but removeable!) undercarriage legs at the top, and below, the original legs soldered together to make a drop-off u/c. Whilst the first trials of this showed promise, the u/c did not always drop cleanly and, having come close to crashing the model during increasingly violent manouevres in an attempt to shake the wheels off, this approach was eventually abandoned. More beautiful wheels-up pictures did though convince me that I didn't want to revert to the fixed u/c option.


Recently, I have found that such is the power of these little brushless motors that the model will generally take off from grass without the aid of wheels at all - so now both sets of wheels are surplus to requirements!

May 2008 (More 'wet' pictures)

Over the Winter of 2007/08 I had hoped to get the opportunity to fly the Sealand from floodwater but, one way or another, it never quite happened. Early in May, clubmate Mike Roach finished his Catalina (another Ivan Pettigrew design) and persuaded me that we should don waders and stride out ot a sandbank in Christchurch harbour.


This proved to be a very successful outing - click on the above link for more watery pictures. Steering using differential throttles (coupled to the rudder stick) was very powerful and the tip float retention mechanism worked well. I was also delighted to find that the inside of the Sealand remained completely dry.


All in all, a very satisfactory way to round off the Sealand's first year of flying.