Corky's Build

[Corky]

Thanks Kent...I remembered you had something on yours but I did'nt remember what.....Did you weld it fast or did you wiretie it to the cage ???

And thanks Papee for the clarification...As you can guess it's a tough decision with so many choices on what to do...I was checking out the weight and the 1/8th inch wire is amazingly heavy for what it is...I'tll add up quick if you go overboard on the grid...

[kent]

Fencing wire is welded to the cage. Just a quick shot with the MIG...

[Corky]

I made more progress this week even though it's like an oven outside !!! 90s and high humidity...I'm wooped until I get home but luckily I have a dehumidifier in the shop and it cools the garage like an AC unit...Anyhow I finished up the rear cage rudder mounting tubes and the reinforcements...Check out the cool diamond shaped design I came up with for the bottom run of the cage !!

[Corky]

The 1/8th inch cold rolled steel wire is going on the cage here's pics of the first layer...I ended up going 5 inches on center for this phase...All I can say is WOW...What a pain...This stuff is very tough to weld it wants to distort{at the weld} if you don't get it perfect in the first few seconds...I've got the hang of it now though...A quick tack on each side of the wire starting on the EMT seems to work the best...

[Corky]

I just did'nt see the need to add a big overlaping second grid to make squares...I simply split the area in half and went with it...It's very rigid and will protect the prop to a degree I'm happy with...I've had my other mini on the water for 30 years and don't even have the secondary mesh on the main cage...So here's what the secondary mesh looks like for this build..

[Papee]

I think you'll be fine with it you'll just have to watch your passengers and make sure they keep things secure that may get into it like plastic bags and such. I'm always bending my 4x4 wire somewhere to get my hand through to adjust he carb or something so the bigger openings are good in my opinion.

[Corky]

I finished up the front swiveling seat...The quick release works well and the two are a tight fit...Swivel release arm is out the right side...I've added the grab bar{attached to the seat } so it gives the passenger something to hold on to if need be...But it's low enough to be out of the way for casting and reeling in the fish...Both the operator and passenger seating has an aluminum reinforcement plate under them for added strength..

[Corky]

Next on the list is the rudders...I'm going with the aerodynamic rudders instead of the flat style...After some investigation there seems to be little difference in performance between the favorite NACA profiles being used for the rudders so I went with the NACA 10 profile...Here's the end caps in the process..A sharp eye will see a difference in length on the left..Two of them will be the bottom end caps with the extensions for the steering hardware...

[Corky]

I'm using .040 5052 for the rudder sheetmetal for a few reasons..The biggest being I want to weld the end caps,aluminum tubing, and all the joints on these..
So here we go...I found the centerline of the 40x40 inch sheet and bent it in a 90*angle...I folded it together at the back and added a 1/4 inch aluminum end cap between the sheetmetal so I have a nice, thick back edge...Welded it up and then ground the weld down for a seamless look on the trailing edge...

[Corky]

I cut the airfoil shape from 1/8th inch plate and installed them inside the sheets...I installed them flush with the sheeting on the bottom and tacked them in...What this did was hold the sheet to the exact dimensions needed and also make a backer for the next phase of assembly...I then used my bottom pieces also cut from 1/8th inch plate and sat the whole assembly on the bottom plate and tacked them together...There also was a series of plug welds on the bottom plates to join the two together...Next up is dealing with the foam...

[aerokirk]

[Doozit20]

I like it. Welding that .040 must have been a pain in the you know what. Great job.

[Corky]

After talking with aerokirk in his build thread I decided to make my own hot wire foam cutter to fill my rudders with a contoured foam sheet...I had a bunch of transformers but none had the amps needed to safely heat the 50 inch span of the nichrome wire...So I ordered one from Jacobs ...For anyone looking to buy a transformer, nichrome wire, and other materials needed to make a hot wire foam cutter here's the link.. http://jacobs-online.biz/index.htm


Here's my foam cutter and bow..It uses a three gang box..An on/off switch with a pilot light to show the power is on..This allows me to dial in the dimmer and leave it set then just cut the power at the switch...I used extension cord ends to connect the unit to the hotwire bow for the easy disconnect...

[Corky]

After playing with the hotwire cutter for a while I dialed it in and cut the foam inserts for the rudders... You need to use some type of non-conducting,non-heat transfering ends for the contour duties...Looks like wood is the easy way out...It's just a matter of cutting the foam, sliding it into the rudders then tack welding the aluminum insert into the top...

Next up is welding the end cap on top of the insert just as the bottom was done...I had some long {as in 18 inches !!} wood bits that I used to drill down through the foam core from each end so my aluminum pivot tubing could be installed through the rudders...I could have easily used some EMT and made up some "teeth" to cut through the foam also but the wood bits were the easy way out for me...After the Sch 40 aluminum pipe was installed through the rudders I welded around the pipe to attach it to the end cap...

[Corky]

Here's a detail shot of the sch40 aluminum pipe and the plug welds...They were 1/2 inch holes so there is more than enough to hold the insert and end cap in place... The pipe will get cut when the cage tabs are welded on and the final measurements are figured in..

[Corky]

Now for the end cap detail...I'm using all metal filler to cover and reinforce the end cap tack welds...All metal is basically a powdered aluminum filler with a clear hardner...When it sets it's extremely tough and waterproof...I've used this filler for years for my automotive restorations and it's the perfect match for this application...A standard body filler would'nt be able to take the vibration and moisture conditions on an airboat..This stuff will probably outlast the .040 sheet aluminum in the long run..

[Corky]

Moving along... The rudder cage mounts are simple... I'm going the high grade stainless 3/8 rod route on this build...It will pass completely through the rudder and will use the nylon spacers between the rudder's aluminum sch 40 tubing and the stainless bar...Not only will this keep the rudders in position top and bottom but if done correctly will hold everything together even if for some reason the hull/cage gets flexed or bent {}....Like I said before I want to give myself every chance to make it home if I slide or plow into something...Pic is the top rudder cage mount and second is the stainless rod being test fitted...A nut and washer gets welded on top of the rod and the bottom gets pinned or keyed...Pics of that to come later...What I need to stress here is that all mounting tabs have been completely plumbed up with the cage and the rods fit perfectly with no deflection or binding...

[Corky]

Before the rudders are installed the engine oil cooler needs to be attached to it's location in front of the prop...The oil cooler I chose is an Earl's Performance Temp-A-Cure part number 41306{6AN fitting size}...It measures 13 inches long,4 inches tall, 2 inches thick and has 13 rows for the cooling duties...I chose this unit because of the low flow resistance and the superior cooling compared to other brands...This will cool as good or better than a cheaper unit double it's size...Here's the pics...

[Corky]

And the cooler in it's final resting place...About 1 inch above the transom...I wanted to keep it low for less of an obstruction...It's 4-5 inches from the prop so it'll get the air pulled through even at a slow RPM...The mount's nuts and bolts will end up getting replaced with some stainless hardware including some nylon locknuts after the breakdown for paint...

[Corky]

I wanted to touch on this next subject while I'm thinking about it...
I feel there's really only two choices for properly preping bare aluminum for the initial coating...First choice would be an etching primer or wash followed by either a sealer or if need be a primer surfacer{and after the work a sealer}...Now, in the past few years the new generation of epoxy primers come in a DTM {direct-to-metal} formula that basically will mechanically grab{as in bond to a sanded surface} the aluminum and seal it without the need for the initial etching primer...

So Here's my own experiment and I'll report on how each component is holding up...The hull will get the DTM epoxy primer/sealer... And the rudders will get the self-etching primer followed by a 2K{urethane primer with hardner}primer surfacer...After any small imperfections are sanded out the rudders will get a urethane sealer applied and be ready for the colorcoat...

So here's two pics of the rudder prep...I can get away with shooting these at this stage, in the garage without too much concern about what's in the garage...I've got an air filtering system and a large fan that pulls the overspray out fairly quick...But the hull prep will be a different story requiring the garage to be spotless and bare...

First coat {green} is the etching primer followed by the grey 2k primer/surfacer... The rudders will be assembled and fitted at this point and will be sealed/topcoated with the hull after the teardown for painting in case they get chips or scratches during the build...