Week 42 - Safety cell mod - Part 3

Hours to date: 382.0


Been working solidly on the cell mod for the last 2 weeks - the end is in sight now.


Had a little delay while I waited for some Kevlar Shears to arrive. I tried cutting the Kevlar with normal shears - no chance! Also the rotary cutter was defeated by this most strong material. The shears are not cheap at £28 - but essential for the job.


I started off by doing a test piece - to see if I could make a sandwich of honeycomb properly. This worked out very well and is incredibly strong even with just one layer of Kevlar on each side.


Next up I 'tacked' the front of the cell in exactly the right position using Flock. I used duct tape and pieces of wood to hold it in the right place while the flock set.


Then it was a case of making up templates in many sections out of cardboard, these were then covered with aluminium tape and given 3 coats of release wax. Taped in place these provided a perfect shape for the outer layer of Kevlar to assume when bonded.


Once the outer layer was set it was time to make up an inner layer that consisted of another layer of Kevlar on each side of honeycomb (Nomex), followed by peel ply.


If this sounds time consuming it's because it is!


It's worked out well though and when the pieces are overlapped the whole thing becomes very strong.


Almost done this now - just a few small fiddly pieces to go around the firewall support area. I will finish by putting another layer on all round of Kevlar - maybe even 3 layers on the part where my feet will be.


The other thing I've been working on is modifying the block that is bonded into the footwell and is the attachment point for the rudder pedals.


I had to change the angle of the back of it to match the new angle of the cell (a side effect of the mod). Also I found it needed to be made taller - by about 20mm to have the carbon bracket fit on it properly. I did all this with micro - as you will see from the photos - and finished up with a layer of glass (same as the factory had done).


Hopefully I will have finished the cell mod by the end of next weekend - which is a 4 day affair due to the Queens Jubilee and Bank holiday falling on consecutive days, Monday and Tuesday. I should be able to make some good progress.

Test piece bonding and after cutting

Kevlar Shears

Tacking in place with Flock

Cardboard templates with aluminium tape

3 coats of wax helps them release from fabric

Partly done.

Almost there.

Block needs to be made taller to fit Carbon bracket

Cardboard to make micro assume the right shape

With micro in place and drying

Block done (pre layer of glass)

Week 40 - Safety cell mod - Part 2

Hours to date: 352.5


Getting closer to bonding the safety cell mod but first there is a lot of prep work to be done and that's what has been taking up my time this week. Got a case of 'Sanders elbow' doing this.


I also spent quite a bit of time doing test runs with tape holding the front of the cell in the right position - my earlier calculations seem to be right. 5 inches at the base and 7 at the top. A side effect of changing the angle of the footwell is that the Micro block that the rudder pedals get attached to will have to be modified to sit flush at the right angle - easily done, just got to add more material to it.


Just as well I didn't order the BRS option on this kit - there would be no room for it. The space I am taking up with my mod is normally reserved for the Ballistic parachute and explosive charge.


I also bonded in the seatbelt reinforcement plywood blocks and sanded everything down smooth so nothing can chaff the belts. Still got to fill in the honeycomb with micro on that job.


Finally I made the top access hole in the fuselage a little larger so access will be easier for the cell mod.


Hopefully this week I can begin the bonding of new Kevlar and honeycomb to the front of the safety cell. This will be done in several stages - most likely a 'tacking' stage first with flock on the struts then once that is dry the outside layer of Kevlar followed by honeycomb in the void and then finally another layer of Kevlar on the inside.

Front of cell roughened up for bonding

Ditto at the other end and on the firewall support struts

Seatbelt reinforcement flocked in place and sanded

Upper access hole made bigger

Week 39 - Seat belts and Safety cell mod

Hours to date 343.25

Made some decent progress over the long Bank holiday weekend.


I took the plunge and cut the front off the Safety Cell. 


It will need extending by 5 inches at the base and 7 inches at the top. Such is the freaky nature of my long legs!


The upper part curves inward - hence the top being extended further - that way my toes won't hit the end when full lock with the rudder.


It was a bit of a mission to cut. Kevlar is super strong and destroys the Dremels cutting wheels. I went though my 2 best wheels and then about 12 of the cheaper cut off wheels. All in all took about 4 hours to mark and cut.


The weird shape of the cut is due to the safety cell being attached at the front lower portion by a huge amount of Micro. Rather than grind all that away I just went around it.


A further complication is the carbon reinforcing struts that come back from the firewall. They will get in the way of the front lower part of the safety cell when it is moved forward. So I will have to modify the shape of the cell in those areas to accommodate the Carbon struts.


I also cut out the lower and upper access holes - which are needed anyway - but needed now so I can work on the outside of the cell when I extend it.


I plan to attach the front of the cell temporarily in the right position with strips of plywood and 'bondo'. (A technique I learned from Mike Arnold on one of his videos). It's going to be a mission to do this mod - also I have no experience of working with Kevlar and have heard that it is hard to wet out properly. Still it's got to be done. Comfort in the cockpit is paramount!


Next up is the seat belts. The manual shows the two plywood reinforcement strips  already in place. Mine as you can see from the photos were not done. Studying the photo in the manual I saw that this area has been reinforced by carbon. So I've applied two strips to stiffen up this area and distribute the load some more. When that is dry I will add the plywood reinforcements with a load of Flock.

Micro at front of cell

Footwell of cell before marking or cutting

Bingo!

View through to firewall and carbon struts

Seat belt holes and reinforcing plywood - pre fitting

Plywood blocks now shaped to fit better to the cell

Carbon reinforcement - prior to bonding on plywood blocks

Lower access hole cut

Remnants of cutting wheels - Kevlar is tough stuff!

Fuselage dolly

Finally finished the fuselage dolly.

It took me a bit longer than planned as I wasn't feeling the best after suffering from another cold.

All done now and fits good.

I don't think the paint stand will work for the rear of the fuselage - it's too high - so I may have to build something for that. It will be pretty straight forward - just a mini saw horse type thing with maybe carpet or foam on top.

Hope to get this sorted soon and actually make some progress with the kit! It's been a while.

I'm thinking that one of the first jobs will be modifying the safety cell - so I have to determine by how much. While I'm thinking about it this will mean a lot of sitting in the cockpit and making plane noises...

Dolly partly made

All done - fits good

The great swap

Well not much has happened since I last posted.

I had my brother staying with me so didn't get much done (other than building the wing stand).

Also Pete stalled a bit on getting back to me about the wing swap and in the end told me he no longer has the room for storage.

So I ended up having to find a new place for the wings. Luckily my friend has space is his garage so the wings are there now.

The fuselage is in the garage okay but everything is a bit of mess at the moment - so I need to tidy up before starting any jobs.

First job after tidying up will most likely be to build a dolly for the front of the fuselage. I plan to put the rear on one of the paint stands and see how that goes. I may have to build a dolly for the rear fuselage - but for the moment we'll see how we get on without one.

Hope to build the front dolly this weekend.

Fuselage finally in the garage

What a mess

Week 33 - Wing stand

Finally got the wing stand finished - it took three times as long and cost twice as much as expected. This rule seems to hold true when building a plane (or boat).


Also thought I would put a couple of pics in of the plywood washers that I made for the bell crank. Pete turns a single piece out of Nylon block. I don't have a lathe (or those skills) so I made 2 separate pieces of plywood. All very snug and no movement in the bell cranks now.


I'll hopefully get to swap over the wings and fuselage during this Easter weekend.

Small washer in bearing

Then larger washer on top

Port wing - up to speed

Insulating foam in wing stands before cutting out

Wing stand in progress - one end nearly done

All done - now to see if the wings fit!

Wings fit very snug - no movement

Viking engined Twister in Oz

The Australian Twister agent is putting a Viking engine in his one.


It will be interesting to see how it goes for him.


I wonder where the radiator will go?


Should be an interesting cowling exercise to follow.


These pics are of a US based Twister that is also having a Viking engine (I think).

Week 31 - Port wing update and wing stands

Hours to date: 305.25


Passed the 300 hour mark - so if my estimate of 1,500 hours holds true then we are 20% of the way through this project. Hopefully I can keep up my 12 hour per week average.


I've brought the Port wing up to the same standard as the Starboard wing now. 


There is nothing really left to do without the fuselage so I am now building a wing stand so the wings will have somewhere safe to sit when I take them up to Pete's.


I also found some pics of a newly registered Twister in the UK. Another fixed gear one - although with the old style tailwheel. Paint job looks good.

Week 30 - Fill, sand, fill, sand etc.

Hours to date 295.25


Started on the filling now. Pretty easy going. But man does that filler stink! Lots of good ventilation and a mask is essential. Quite enjoy this job except for the smell.


Pete says to use Micro as a filler on weight critical parts - such as control surfaces.


So the Rudder as you will see below has Micro on it, the wings and tailplane have normal filler.


I also decided not to be so lazy and completely reinforce the inside of the rear rib behind the flaps. Really poor access for this job - so a bit of a mission but got there in the end. Not a pretty piece of work so no photos!


Switched wings now too so I am bringing the Port wing up to scratch with reinforcing of the root rib with Carbon. After that there will not be a lot left I can do - so soon it will be time to swap out with the fuselage.

Fiberglass 101 DVD - Highly Recommended

This DVD is just brilliant and if you are considering building a Twister then you should definitely buy it and watch it a few times.


It won't win any Oscars for acting, directing or cinematography but to hear a guru such as Sam James share his decades of experience and knowledge like this is just invaluable. It is almost totally practical too - only a bit of history and theory at the start then it is straight down to how to build parts. Then in the second half Sam covers building moulds. 2 hours of gold.


All-in-all a must have for any budding builders out there.


Buy from Tech books on the below link.


http://www.actechbooks.com/products/act193/

Silence Twister Hybrid

I've been thinking...


With the ever rising cost of AVGAS and the ever increasing power of batteries there will come a time when the humble piston engine will have had it's day.


We are some years away from that moment but in the meantime the most logical solution is a hybrid.


Because batteries take so long to charge up again this is the only practical solution for the foreseeable future - until there is a step change in battery technology.


Click on the pic below for a bigger view which outlines my 'mark 1' configuration.

Advantages of this set up are: 


Reduced running costs (Jet A-1 can be bought for less than half the price of AVGAS here in the UK - plus the battery charging cost is a tiny fraction per KW of power output). Also the Twister would only need approx 45kw continuous as a sustainer in the cruise - so fuel burn of the turbine could well drop to 20 LPH.


Potentially quiet operation in noise sensitive areas - battery use alone for climb out to cruise (5 mins) or approach to land. 


Greater fuel availability (Jet A-1 is much more widely available than AVGAS). 


No loss of performance with altitude (actually the turbine runs better the higher it goes).


Potentially more reliable. (In the early days this will not be the case but turbines and electric motors have extremely good track records of reliability so should be able to be made this way in this set-up).


Reduced drag. (With a very narrow cowling and only a small NACA inlet on the bottom plus the thrust from the turbine this has potential to be a more efficient setup than an air cooled piston engine).


Increased performance. (The electric motor produces phenomenal torque and 135hp for a 60 second peak, combine this with the thrust from the turbine and the climb rate would be MUCH better than standard - also the cruise speed would most likely be higher, or the same speed but with a much reduced fuel burn)




Disadvantages are: 


Initial cost of turbine and battery (both unknowns at the moment and the Bladon turbine is not in serial production yet). 


Potential noise issues with the turbine (if it cannot be made quiet). 


Weight (I believe the battery will push this over the traditional air cooled piston set up for weight).


Approval. (I can see the LAA and CAA taking a conservative approach here and not liking this one bit! So the UK may not be the place to take on such a challenge - the USA or NZ with their Experimental categories would be much better for catering with such innovative thinking)




Whilst the technology and affordability are not quite there yet it certainly points the way forward.


Maybe one day we will all have a wind turbine and solar panels on our hangers charging up our plane and be able to fly for little to no fuel cost.


As Howard Hughes would say (most likely repeatedly) "It's the way of the future".


Link to a video about the Bladon Jet here:


http://www.youtube.com/watch?v=pUf_NFOM1L4&feature=BFp&list=WL0DCC83F4EC5EF376

Week 28 - Full and free movement

Hours to date: 275

Well the starboard aileron is now pretty much complete. Just got to add the counterweight and it's done. The factory were very kind to send me a replacement bell crank bearing free of charge - thanks Matthias!

Quite a time consuming task fitting the control surface and getting it to have the right deflections without snagging on anything. Got there in the end.

The counterweight hole had to be made quite a bit bigger but the pushrod hole and aileron root end just needed fine tuning.

After that it was back to the root rib to reinforce with carbon strips. Worked out easy this time now that the edges of the rib were smooth with a little ridge of micro on the top.

It will be time to switch back to the Port wing very soon and get that up to speed.

Fully deflected down - 90mm (wing is upside down)

Fully deflected up - 100mm

Inside wing view of the bell crank and pushrod.

Micro ridges added to the edge where the carbon reinforcing is to go.

Carbon in place - went on quite easy with the ridges.