D.B. SPORT @ SCALE SE5

John Rickett 102 · March 5

The mould, having now been used, benefits from the previous coats of release wax so only 5 coats were applied this time.

Here, the second rocker cover is curing while the first one, after 30 hours is now sufficiently hard that it can be cut with a rotary disc. Its been cut right down to be as realistically proud of the cowl as I can make it (without being able to measure the real thing) leaving tabs which, once the cowl has been suitably slotted, will provide a firm fixing.

John Rickett 102 · March 6

The second cover was released from the mould after 18 hours. I'm pleased to say it came away easily which I think shows that the initial coats of wax are still working and so less coats are required for subsequent lay-ups.

One unexpected benefit of using 25gm cloth as the base layer was how smooth the surface is. I'd used the fine cloth to ensure that the fairly tight curves were followed without using gelcoat, which I don't seem to be able to master (I'm sure its me as others have success) however, the surface is much smoother than starting out with 50gm cloth, which is what I've done previously when making something with gentle curves like a cowl. I suppose this is an obvious discovery now though its something to remember for future lay-ups.

A plus for using fibreglass for this task instead of getting another set of ABS mouldings is the weight, the undamaged ABS moulding weighs 23gm, the fibreglass repalcement, 17gm. Its only a few grammes of course and up at the front end doesn't affect the cg, but an interesting observation that fibreglass can be lighter than ABS.

John Rickett 102 · March 9

With there being no damage to the exhaust headers and as the whole model is firmly in the ‘sport’ category, the headers were used again in a similar position as before. The exhausts should exit the cylinder heads (if there were any) but these were just put as low down on the rockers as possible.

Having only used a few layers of glass cloth, the walls of the rocker covers came out at 0.5mm thick which provides little support for the exhaust stubs. Small pieces of 1/8” ply were added to support the joints, I thought this prudent as its likely the exhausts could be used as handles when removing the cowl, so didn’t want too much flexing and eventual breaking of the fibreglass bits.

All the main components have been completed now so it’s a waiting game for the weather to improve to get on with painting.

John Rickett 102 · April 4

After a protracted wait, the weather eventually decided to cooperate in providing suitable painting conditions.

The cowl was given a couple of coats of 2K primer, rubbed down and then KlassKote colour applied. The colour had been mixed from other standard tins, fortunately some of the paint from the earlier restoration had been saved . The difficult bit was mixing the (Part B) catalyst so that the dried paint had the same sheen as the rest of the model - I wish I had written down what I did earlier. After 4 attempts (and 3 rubdowns) this will have to be near enough.

The radiator shutters, rockers and exhaust should be easier as there isn’t a requirement for matching.

Everything will be in 2K paint to resist glow fuel attack.

EarlyBird · April 5

Immaculate, as usual, and that's only the primer?

Steve

GrumpyGnome · April 6

Certainly already a much better finish than the full size ones probably had......

Outrunner · April 6

1 hour ago, GrumpyGnome said:

Certainly already a much better finish than the full size ones probably had......

Equal to the Old Warden SE5a...

John Rickett 102 · April 6

Well chaps, as much as I don’t like repairing, the earlier damage didn’t warrant discarding of the model so thought it best to try and do an acceptable job prior to selling. Selling has been the intention for some time as it takes up valuable space. Over the years the model has been flown intermittently – I’d rig it, fly it and enjoy the ease and grace but because, once rigged, it’s the only model I can get in the van and then occupy a lot of space in the shed, it’s had an alternating frequent flyer, hangar queen, type of life.

The model is over 25 years old, one of the earlier one-piece wing types. Eddie Stoker, when he bought the company recognised that being able to break down the model into smaller, easier to rig pieces was the future, but this one pre-dates that. It also has Mick Reeves (handed) flat wire rigging, which improves the structural strength so will withstand quite high G forces, not that’s what the model was intended for, this though only adds to the rigging time.

Do you think a bit of weathering or patina would look more realistic – it is only a sport model after all?

John Rickett 102 · April 12

The extra bits have now been painted and attached to the cowl.

This is as far as I can get until the engine has been returned from repair. With the uncertainty about how long it would be to get a replacement crankcase, if there was one of the imperial thread type to be found during the Laser Engines clear out, the decision was taken to get one of the experienced LMA machinists to clean up the damaged front face and, if necessary, fit a shim to make good again. Should a replacement crankcase eventually be found, it could still be used.

The model will now gather dust again for a while but with the weather now more suitable for painting its on with the next project...........

John Rickett 102 · April 22

The engine has now been returned following the repair and check of the main rotating components. Its been bench run and declared fit for service.

Installed and ready for in-situ running - once the rain stops!

John Rickett 102 · May 12

Having installed the motor and run it, some spitting back when nearly at full throttle was evident from the right hand carb. I suspected a broken valve spring (rare but not completely unknown) as I’ve seen before that a Laser can continue to run with a broken spring, but with the rocker cover removed all looked good.

Back in the workroom and with the head off, some paraffin was poured into both intakes to check for leakage. Sure enough it wasn’t long before the paraffin appeared in the cylinder head and the level had dropped in the carb intake, so - exhaust valve good, inlet valve not.

I thought it would be a fairly simple job to remove the valve, check the faces and lap the seats. Not wanting to run the risk of losing a collet, I tried working with the cylinder head and hands in a large plastic bag, but the bag fogged too quickly and I couldn’t (with my aging thumbs) push against the springs far enough to release the collets. And all the time I was worried that if I lost a collet, it would effectively be the end of the motor until (if) collets are included in the spares that have been slated to be available.

I have a later version of the 200v which was planned to be used in the SE5 if the original couldn’t be repaired, though I wasn’t expecting a problem with a passing valve – time to swap motors.

Apart from the external cosmetic differences, the dimensions are the same. The backplate also has the same spacing and hole size as the earlier engine so it’s a simple swap. The original engine can go into a cupboard until such time as the situation with Laser spares is clearer or I can improvise a valve compressor.

The repair efforts came to fruition with having two flights last weekend, the weather was gloomy and perhaps a bit gusty for this type of model but nevertheless successful, so it was a satisfying end to the repairs.

Before I put the model up for sale elsewhere, does any RCM&E forumite want a DB SE5?......Proven flyer, covered in cloth and painted with 2K fuel proof paint, Mick Reeves silver soldered rigging, Futaba servos, closed loop control on rudder, both elevator halves and tail skid. The engine mounting is for a Laser V twin, if another engine was to be fitted the (plywood) mount would have to be released from the bulkhead, or simply cut off. The bulkhead sits 138mm back from the front of the model, the engine mount itself is 105mm from the front. The 200v is available if the complete model is wanted.