Rubin

Brian wrote: I like your choice of colour scheme Mike, its almost like looking at two different models. Do you seal the balsa before covering, and do you use a primer on the overlaps in the film?

No and no. IMHO, the last thing you would want to do is seal the balsa before applying any heatshrink film. You want any air to be able to expand into the grain of the balsa as it is heated. To be honest, covering a foam wing using film is not easy because the foam is airtight. So for a built up wing you might seal all the edges before shrinking the film, but with a foam wing (or any soling surface) I lightly tack corners and edges every 10cm or so and then work from the centre outwards. This avoids trapping too many air bubbles.

As for sealing the edges of overlaps, I know Jon does seal his overlaps after covering (perhaps he can link to the product he uses?). I don't and get away with it partly because I do not use fuel and also because I haven't seen the need to do so. The only area where I did use Cover Grip (Balsaloc) is in a few places where a film edge was against the fibreglass bandage. But I don't apply Cover Grip over the whole bandage because I don't want it to stick too much here. I've done it in the past and as soon as you get a wrinkle it is virtually impossible to remove.

Phil Ford wrote: Mike, if the dark blue is Oracover 52...

Why would you assume Oracover. You know I'm [strike]a tight git[/strike] careful with my money.

MikeSeale wrote:

Phil Ford wrote: Mike, if the dark blue is Oracover 52...

Why would you assume Oracover. You know I'm [strike]a tight git[/strike] careful with my money.

At the present time that is good policy.
:lol: I did not assume Mike but I thought you might have some old stock of Oracover hanging around that someone gave you.

MikeSeale wrote: .
As for sealing the edges of overlaps, I know Jon does seal his overlaps after covering (perhaps he can link to the product he uses?)

I use this, same one has done several models.

signgeer.com/brand/sealit-pen

Although I don't seal all the overlaps, only edges of the separate trim pieces, especially any points. For overlaps, I just make sure they face downwind

A few statistics from the completed model now that all the servos are in.

The ready to fly weight is 3.9kg which is 400g lighter than Wolfgang Matts original which he quotes at 4.3kg with a YS120.

And I ran the motor with a 14x12 prop on a new 8s battery that was in supplied state (storage charge). This pulled 73A and I think it was spinning at over 9k. I'll need to check this again because my tachometer kept going to zero - do optical tachometers wear out? Anyhow, I think the motor will be at least as powerful as a YS120.

All in all, I'm very pleased with these figures and can't wait for lock down to end. I imagine that it will be very busy at Cashmoor when we're finally allowed out.

Mike wrote

do optical tachometers wear out?

I'm probably teaching my Granny to suck eggs but I've found optical tachos are very sensitive to background light.

I was thinking the same...Very bright light in the garden yesterday. I'll try to get another reading on an overcast day.

Mike wrote

I'll try to get another reading on an overcast day.

Don’t worry Mike, as it’s not IC powered as long as there isn't anything which would be damaged by being blown about it’s quite OK to do it indoors in a darkened room.

joneb wrote: Mike wrote

do optical tachometers wear out?

I'm probably teaching my Granny to suck eggs but I've found optical tachos are very sensitive to background light.

I used a piece of black silicone tubing as a 'lens hood' over the sensor on mine, and found it to be much more reliable.

That's worth trying, thanks.