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Ducted fan build

Old 07-06-2009, 07:55 PM
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srw1960
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Default Ducted fan build

Ok here goes my first build to be shared here..so if I do something really stupid cut me a little slack....

I am building a ducted fan air boat. It will use air rudders and be a small v hull of my own design I do not have any plans other than whats in my head so bear with me..
I am going to try to keep the weight to a minimum so I am using balsa and lite ply for the structure and after it is all built I will lay 2 layers of light weight glass to sturdy it up..My intention is to get this running good and use it as a plug to make a mold and then some fiberglass hulls ..
I am using a 89 mm fan unit with a brushless motor,14.8 volt lipo battery,40AESC,mini servo for the rudder. ( I dont think ill need that much torque to turn it) and a spektrum radio system...

I started by drawing out the hull shape on poster board.once I had it where I wanted it I cut it out to give me the deck..Then I marked off how far I wanted to space the bulkheads out.
then I drew out the transom and cut it out to check the fit against the deck..once I had the transom fit and shaped where I wanted it I used it as a template for the other bulkheads and adjusted the width and angles for where the bulhead would be in the hull..once everything was drawn out on the poster board I cut them all out..

Once I had all the bulkheads I taped them into place on the bottom of the deck to check all the angles and sizes to ensure there was a nice smooth transition on the sides as well as the bottom of the hull remeber this is a shallow v hull not a flat bottom...I made adjustments as needed to the poster board templates until everything looked good and the dimensions all were even and then I transferd the shape to some 3/32 lite ply and cut out the bulkheads..and also cut out the top deck from a piece of 1/16 balsa...

Ok now for some fun..I set each bulkhead in place making certain the deck remained flat at all times and using a square block to make sure they glued in straight. I glued all the bulkheads in place...Next I had to cut some holes in the bulkheads to make a channell down the center to make room for the fan unit I did this for 2 reasons one was to keep the CG low and the other well just cause I thought it looks good..I used the trim ring from the fan unit set it in position over the bulkhead and traced around it to get the shape I needed then I used a dremel tool with a spiral cutting bit to carve the holes out and then a light sanding to finalize the shape..

I made blocks to attach the fan unit on to and glued them in place and then I set about making a hatch to go under the fan unti as that is where I will mount the radio gear.the lipo batery will be accesed threw this hatch as well..

Thats as far as I got today I will work on it more tomorrow and post the progress..any coments or sugestions will be much appreciated like I said im kinda new to this air boat thing and definatly new to electric power...

Yall have funnnnn and take care
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Old 07-06-2009, 09:30 PM
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DONS BOAT WORKS
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Default RE: Ducted fan build

I'm watching this build!!!
Old 07-06-2009, 10:42 PM
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srw1960
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Default RE: Ducted fan build

Cool sounds like you like it so far..Ill post more pics tomorrow have to run to the LHS and get more lumber. the cowl I am planning on will take a bit of wood to build..this will look pretty good when done I do beleive..any thoughts on what I have so far??
Old 07-07-2009, 12:36 PM
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Default RE: Ducted fan build

It is looking pretty sharp srw1960. If you are concerned with weight, you could probably get away with one layer of fiberglass cloth. Good job. Keep the pictures coming. Dennis
Old 07-07-2009, 04:08 PM
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Default RE: Ducted fan build

I don't think that weight should be your greatest concern... You are running a brushless and lipo setup - have you ran the fan yet? how much thrust does it have?
My guess is that the hardware you have in the boat will be more than capable of moving the thing at respectable speeds (I am new to ducted fans so I may be wrong)
Keep the build going - I will certainly be visiting while I wait for the glue/paint on my hovercraft to dry! [8D]

EDIT: and by the way, make sure you mount that duct securely! I learned the hard way: [link=http://s215.photobucket.com/albums/cc21/ISIRC10/?action=view&current=LOLfail.flv]Bad Driving/Motor Mount[/link]
Old 07-07-2009, 06:47 PM
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srw1960
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Default RE: Ducted fan build

I am fixing to go out and take pics of todays progress I stayed up till 3 am working on it..I have not fired up the fan yet the esc I bought came in and the rating on the package and what it was suposed to be rated at are 2 differant things and im afraid ill fry the esc and who knows what else may fry in the process.So until I find out more ill wait to spin it up BUT its a 89 mm fan biggest one I could find and its suposed to have like 1150 grams of thrust it was the bigest and strongest one I could find.
And I have mounted wood blocks to mount the fan unit on and I promise they aint going no wheres.youll see in the pics if you think I need more then let me know and ill beef em up a bit...Ok nuff talk Ill go get some pics..
Old 07-07-2009, 07:18 PM
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srw1960
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Default RE: Ducted fan build

Ok heres pics..I got a good start on the cowl today got the bottom plate made and mounted with 6/32 stainless screws and t nuts..fabricated a battery box last night err early this am rather..I will epoxy a deans plug to the bulkhead so I can keep the radio box sealed up good the battery will be accessed by removing the cowl I have made the cowl to where only 3 screws will hold it...mounted a piece of lite ply to mount the servo and you may be wondering what the little block of wood with the fuel tubing coming out is for.. thats my antenae mount...the antenae tube slides into the wood block from the top of the deck it will be epoxied in after paint I put a small piece of brass tubing in the bottom of the block and drilled a hole through the servo plate and stuffed a piece of tubing through and stuck it onto the brass tube this way when I change receivers I wont have trouble routing the antenae wire out the tube...the hull sides went on again I used a pice of poster board to make a template and then cut the balsa and laid it on fit like a glove....I will fill all the cavities with foam for flotation and lay the bottom of the hull on tomorrow and see if I can finish the cowl..just had a cool idea for the cowl Ill fab it up tomorrow and suprise you guys with it..I bet you like it...

Yall have funnn and take care
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Old 07-07-2009, 07:22 PM
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srw1960
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Default RE: Ducted fan build

more pics
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Old 07-08-2009, 10:19 AM
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Default RE: Ducted fan build

Nice build!

I'm curiuos, as to how it will run, as an airboat will never reach the speed a ducted fan is intended for (200Km/h), so the air speed will be high, but will the thrust be high enough?
I see only large, low pitched blades on 'conventional' airboats...

Finish it and we will know!

Regards, Jan.
Old 07-08-2009, 11:33 AM
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Default RE: Ducted fan build

I see you've thought ahead and put in a drain tube for the center portion of the hull....That IS what that green tube is, right?

Do you plan on putting a layer of epoxy on the inside of the hull?
Old 07-08-2009, 06:01 PM
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srw1960
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Default RE: Ducted fan build

MMMMM no..the green tube is a guide that the receiver antenae goes through to let it pass through the servo mount and out of the top deck...I plan on sealing the cowl down with a silicone gasket if after a couple runs I see a water in the hull problem I will install tubes then.and yes I plan on rolling a thin coat of epoxy in it and it will be covered in glass as well..
Ok for todays events..it was UGLY....made progress on the build and I will post new pics in a bit I need to tell you guys what happened so you can avoid the same mistake.
I puchased a esc for this from one of the chinese vendors on e bay.the description listed the specs as being rated for 3 to 16 volts lipo or nimh batteries,and 40a continuose curent rating..well it came in and as I was looking at the package I saw a spec sheet and read it. it said it was rated for 3 to 13 volts and 40a SURGE..30 a continuose..contacted the vendor and after a 3 day wait for a reply he said it should work ok to try it and if it doesnt work he will replace it or refund it..ok so I hooked it up and followed the directions, they said to hold full throttle while hooking up the batery so the esc will auto detect and set itself..well I did..BIG MISTAKE and never hold these things in youre hand...It imediatly exploded in my hand..thank god I have fast reflexes cause then it caught on fire..im lucky my hole shop didnt go up with all the balsa dust laying around.(yes I keep a fire extingusher in my shop)so anyway please learn from my lesson avoid chinese parts and if you do use them use them cautiously.....

Ok got the bottom hull laid on and Im working on the cowl hope to have it done later tonight..Ohhhhh and after the fire I wanted to see how much thrust the fan will put out.I dug around and found a esc I had and hooked it up to it I used a standard what is it 7.2 volt car battery pack and the motor is rated for up to 14.8 volts..anway I fired it up and OHHHH MY GAWD..it was all I could do to hang on to it and its running at half voltage...I bought the biggest badest highest thrust fan I could find and I think I may regret it..may have to go to a lower voltage lipo pack to be able to handle this thing..Pompebled I do beleive this will have more than enough thrust to get this motivated very well..

Ok Ill go take pics now...yall have funnnn and take care
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Old 07-08-2009, 07:58 PM
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Default RE: Ducted fan build

Well, I guess we all live and learn - some of us are just better at letting out that magic blue smoke than others!

About the fan having a lot of thrust - that is awesome to hear! keep that power on tap and you can eat a nitro boat without even noticing that it was there! Oh, and the faster you go, the farther you fly, the harder you crash - Build a sturdy boat and you will be able to laugh it off when you hit a wave and do a few backflips (and get it on video of course!)

On a more serious note, kinda sucks that your ESC went poof - hope that doesn't slow down your build
Old 07-08-2009, 08:12 PM
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srw1960
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Default RE: Ducted fan build

It falls into the category of s!!t happens...and I bought a new esc this afternoon from an american vendor cost more but the old saying is true..get what ya pay for..

I will do my best to finish the cowl,mount the servo and I have to engineer the rudders now and make the control rod for them tomorrow..gonna be a hot one here inHouston thank god I have ac in my shop..

Ill keep building inspite of the esc incident plenty to do with out it..hopefully itll be in glass by this weekend.
Thinking about making a jig to mount the fan onto and measure how much thrust it has..well yall have funnnn and take care..more to come
Old 07-09-2009, 12:29 AM
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srw1960
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Default RE: Ducted fan build

Ok went back out in the heat a bit cooler after the sun goes down but not much..and I have the cowl finished and the rudders enginered and ready to mount tomorrow they are just tacked on for the pics...I want to ask yall's opinion..I was going to take a piece of 1 inch dowel rod about 5 inches long and sand it down to a sharp point and mount it in the center of the cowl opening..overkill or not???? anyway enjoy the pics and itll be glass time soon
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Old 07-09-2009, 06:25 AM
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pompebled
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Default RE: Ducted fan build

ORIGINAL: srw1960
.I dug around and found a esc I had and hooked it up to it I used a standard what is it 7.2 volt car battery pack and the motor is rated for up to 14.8 volts..anway I fired it up and OHHHH MY GAWD..it was all I could do to hang on to it and its running at half voltage...I bought the biggest badest highest thrust fan I could find and I think I may regret it..may have to go to a lower voltage lipo pack to be able to handle this thing..Pompebled I do beleive this will have more than enough thrust to get this motivated very well..
I think I get your drift...;

I once tested an airboat set-up with a 700 motor and used my regulated powersupply on the 15V setting.

I've seen dust coming out of every nook and cranny of my workshop and everything light enough took off in flight...

Good luck on your build!

Regards, Jan.
Old 07-10-2009, 10:59 PM
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srw1960
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Default RE: Ducted fan build

Ok a little more progress...mounted the rudders they work good just have to get them hooked up to the servo. you can see the conecting rod I made to join them and I will cut small pieces of tubing to fill the gap between the rudder and the cowling...since no one comented about the skike?cone or whatever you want to call it. I went ahead and made it and installed it...easy to remove if it just doesnt look good..I like it but I would like to hear from you folks.....heres some more pics enjoy..

yall have funnnn and take care
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Old 07-10-2009, 11:25 PM
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Default RE: Ducted fan build

I like the look of the boat with the cone on it. it kind of completes the look.
Old 07-10-2009, 11:49 PM
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srw1960
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Default RE: Ducted fan build

Thats how I felt about it to..I think its the old sr71 black bird spy planes that had a cone like that extend in front of the intake.. thats what I was going for..glad you like it
Old 07-10-2009, 11:59 PM
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srw1960
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Default RE: Ducted fan build

Thats how I felt about it to..I think its the old sr71 black bird spy planes that had a cone like that extend in front of the intake.. thats what I was going for..glad you like it

dont know why it posted this twice oh welll
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Old 07-11-2009, 08:07 AM
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Default RE: Ducted fan build

Nice job with the cone, the blackbird was the first thing that I thought of when I saw yours... looks like your imitation works.
now just paint it black and give it wings!
Old 07-14-2009, 07:37 PM
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srw1960
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Default RE: Ducted fan build

Ok got started with the glass work today hopefully I can finish it tomorrow and get started on the paint part of this program.

P.S. I HATE FIBERGLASS....
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Old 07-15-2009, 12:48 PM
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Default RE: Ducted fan build

Looks like heavy duty cloth. Strength won't be a problem

You've got a really sharp looking boat there. Can't wait to see some vids!
Old 07-15-2009, 10:13 PM
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srw1960
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Thanks Jasper! and since the entire hull is balsa I planed on the fiberglass giving me the strength It will need..somehow I have a feeling this little boat is gonna haull butt....I finished the glass work today...I layed up the bottom of the hull yesterday and the cowl..today I layed up the top of the hull I wet everything down and I was having trouble keeping the edges stuck down so I tried something and it worked pretty good..I stuffed the boat into a big glad thrash bag stuck the hose from my shop vac in it taped it up and turned the vacum on...sucked the bag in so tight I thought it was gonna pop but it never did even when the resin was kicking off and hot....let it set up good took it out and I was impressed..yes there was wrinkles from the bag if I had a smaller bag I could have worked some of the wrinkles out but it did what I wanted it to do and that was keep all the wet glass stuck down and flat all my edges came out real nice and sharp ...im going to order some materials to use on the next hull and bag it to ..anyway ALL THE GLASS WORK IS DONE YEAHHHHHHHH[sm=tongue_smile.gif]...so now a little smoothing out and its time for paint.oh anti freeze grean and purple are the colors for this one maybee some lightening bolts air brushed on it dunno yet but you can bet itll look as good as it runs...Hmmm perhaps flames since the first esc exploded and burnt guess this is an experiment after all huh???....the weight is still good on this I put 2 layers on the bottom with an extra layer on the nose then 1 layer on top that laped over and coverd the sides and transom and then 1 more layer just on top ohhhh and I coated all the inside with resin while I was at it...after all was said and done yes I added some weight but it is still very very light...only 1 pic today Ill take more tomorrow...
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Old 07-16-2009, 05:54 AM
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Default RE: Ducted fan build

Brilliant! Home made vacuum-bagging!

Regards, Jan.
Old 07-16-2009, 09:15 PM
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Thanks Pompebled!! Ive allways been good at thinking outside the box to solve problems im just glad it worked the way I wanted it to..I found a site that sells fiberglass supply's and materials even carbon fiber and there prices are pretty resonable..Im going to order some bagging material and I allready have the pieces to put a real vacum pump together. so the next hull build will get bagged and I bet it comes out way nice not that this one was bad it was just a bit rougher than I had hoped but it acomplished what I needed it to....matter of fact I think the next hull will be all carbon fiber...

Ok sanded all the glass work down and gave it a skim coat of extra light bondo and got that blocked down and its ready for primer and paint Ill start on that tomorrow..Im real happy with it so far you can see from the pics most of the bondo sanded off whats left is very thin and the weight on this hull is very good I realy think its going to come in as ounces not pounds and ounces for the hull only. and the rest of the gear is pretty light weight..im using a micro receiver with a micro servo and the esc has bec on it so no need for a receiver pack....I am realy excited about starting the paint process tomorrow and yes Ill take pics of each stage so you folks that have wondered about painting these things can see what its all about the actual building and painting are my favorite parts of building boats...

Ok heres pics of what got done today..yall have funnn and take care..
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