norbique

Sorry Mike! I was reading one of your old posts in your build thread and I thought you still don't have a cutter. How stupid. he he
I couldn't work on the tunnel today as much as I wanted to. Other things intervened. Although I cut two pieces of ply to sheet the bottom side of the sponsons.

Another question: How thick ply should I use to sheet the top of the sponsons? The same what I used to sheet the top of the hull?!

racer504

My Feedback: (2)

Yes, 1/32" on top and sides. Run pad is 1/16". Cap on back of sponson is 1/16". The run pad can overhang the back of the sponson by 1/4" to shear the water off cleanly if you like. I have also cut the rear of the sponsons on various angles to do the same thing. Here are some pictures of the rear end of the sponsons of other versions (5,2,3) of my boats. You are building ver. 4.

10x8

Sorry for any confusion.
In the other tunnel thread, a user with black cat avatar wrote about the REK drive. I thought that was you, that's all.
I am aware you run OS drive via pics.

Peter

norbique

Thanks Mike, I like the first photo the most. I think I already saw this boat of yours somewhere, maybe in your build thread?!

Mike, I wanted to ask you something but I always forgot. How much time do you need to make a tunnel? No painting, just the construction time.

racer504

My Feedback: (2)

I doubt you've seen that boat. It was built late last winter and is a 5th version. Only one was built. I tried some things with the sponson angles and I used it as my race boat for the first half of the season. It had trimming issues which I never did resolve.

It takes me about 2 weeks to get one done up to ready for paint. I don't build very fast so I'm sure someone could build one faster than that.

norbique

OK, I must have seen something else then.
Building one in two weeks is fast! I began building several weeks ago and still half way there.

I wanted to ask you Mike what glue are use using to sheet the sponsons? The PU or epoxy? Also what's the process? You tape the ply down while the glue sets?

Here's where I'm at now. I finished the transom (glued it in place with epoxy) and began waterproofing the inside of the electronics box with epoxy.

racer504

My Feedback: (2)

I use the PU glue for all the wood to foam surfaces with the exception of the back end cap. It's hard to clamp or tape so I usually just put it on with some fast setting epoxy. I also poke a bunch of holes in the foam under the end cap to get it to bond better. You can use PU if you want though. You can clamp or tape the sponson surfaces on. Whichever get's the job done is good. Lately I've mostly taped it in place. You will probably need to use a combination of clamps and tape for the run pads as the rear portion needs to be very flat.

norbique

Hi Mike,

I had mixed experiences with the PU glue today. I glued on sponson sheetings and I had places where the glue didn't expand and I had trapped air under the ply. I used tape to hold the ply in place. Maybe I taped it too tight so the ply didn't touch the foam at the center, only on the sides, where the tape pressed it too much!? I ended up tearing parts of the ply sheeting off and replacing them with new pieces. I used plenty of glue on the second approach, with success. It seems I haven't applied enough glue, but I'm not sure. I had no problem when sheeting the hull. Don't know why it happened now.

Here are some photos I made, sponsons are not glued to the hull, I just put them together for the photo.

racer504

My Feedback: (2)

I think when you pulled the tape tight it caused the ply to bow in the center. I've seen that before. I usually put a piece of square ( or rectangle) balsa down the center of the area to be sheeted and run the tape over the top of that. The balsa follows the curve of the surface and puts pressure in the center. You didn't have a problem with the hull due to it's shape. Did you remember to dampen the area? The moisture makes the glue foam up and contact anything close to it. It needs the moisture to cure.

norbique

Yes I sprayed the ply with water and put the glue on the foam. It was probably the tape too tight and made the ply arch. I should have used something to press the ply onto the foam completely, perhaps a piece of scrap foam following the shape of the sponson.

norbique

I glued on the bottom side sheet of the right sponson, so Sheeting the running pads is the next thing to do.
I wanted to ask you Mike, how long does the running pad overhang on the outside of the sponsons? All the way from the back to the front, or does is slowly disappear as it is reaching the front?

racer504

My Feedback: (2)

I try to keep it at about 1/8" thru the flat part of the bottom and then decrease it as you get to the front. It may or may not get to 0. Depends on the shape of the front end. I usually make them blunt but that's up to you.

norbique

I wanted to make the front of the sponsons a little more resistant to crashes so I was thinking of how to reinforce them. First I thought of replacing part of the foam with hard wood and sand it to the shape needed, then I decided to go with epoxy and filler. It came out quite good. I checked the sponsons if they're symmetrical and they are quite symmetric. Not perfect, but it's a hand made thing, not a CNC.
Here's a photo, click on it to see it enlarged, so you can see the epoxy filling at the front.
Good night!

ryan_t888

Looking Good.

Ryan

norbique

I worked on the sponsons yesterday. I glued on part of the running pads. Since I don't have long enough piece of ply to cover the whole sponson at once, I had to do it from two parts. Soon I will be gluing the sponsons to the hull. Mike could you please tell me the tunnel height? I know you used bamboo sticks to pin the sponson to the hull. Can you please explain the whole sponson to hull gluing process briefly? Thank you!

racer504

My Feedback: (2)

Norbique,
Once you have two sponsons exactly alike you ready to attach them. I have a jig made to mark where the pins go but you can do it without one. The tunnel depth for this version is 3/4". I use a simple flat, straight piece of MDF (pressed wood) 3/4x6x24. The pins I use are 4"x3/16 dowel rods. They will mount in the hull 2" from the front and 2 " from the rear. They will sit against the bottom sheeting of the hull. I sharpen them in a pencil sharpener and then drill a small hole in the foam to push them into. Once you have them in, wobble them around so you have some play when you put it all together. Now use the jig plate to mark a reference line on the inside of the sponsons. Add a piece of 1/16 ply to the top of the plate when you make the line to account for the hull sheeting. Make sure you are keeping the flat part of the run pads tight to the working surface when you mark the lines. Now mark and drill the holes in the sponsons. They do not have to be a precision fit. Remember the PU glue foams and fills all these wobbled out holes. Now you can test fit everything. The hull should come to within about 1/8" of the top of the sponsons at it's thickest point. Make sure you can keep the sponsons at 90 degrees to the hull bottom. When you are ready to glue you need to put weight across the sponsons at the rear (only) to keep the sponsons flat against the work surface (the flat part of the run pad that is). Now with the 3/4 plate under the hull from front to back, and centered so any glue that seeps out doesn't glue it to the hull, you need to weight the hull to keep it flat on the plate. Just keep looking at it to make sure it all stays in place. If it looks wrong, it probably is. Be sure to put glue in the dowell rod holes.
Mike

norbique

Thanks for the very detailed explanation of the whole process Mike! Extra BIG THANKS for the drawing!
I took me two readings to understand, so much data at once
I won't be able to work on the boat till next Monday, but I'm looking forward to it.
I'll print your post to have it at hand when gluing.

norbique

I had trouble with the inside running edge of the sponsons. The wood wasn't solid enough. I decided to sand off a few millimeters and filled up the slot with epoxy. It's cured and I sanded it to a nice shape. I guess this will add some more debris protection as well. I made the markings required for he assembly, I made the pins, marked the holes on the sponsons, but haven't drilled them yet. See pictures.

norbique

Finally I got it assembled. I glued the sponsons to the hull.
First I glued the bamboo pins inside the sponsons, then I put the PU glue on the foam (hull sides) and dampened the sponsons (wood). The glue foamed up nicely.
I'm going to sand off the excess glue later.

Happy Easter Holidays to everyone!
Norbert

Cornelp

Looking excellent! If I am really nice, can I get the plans? That would be a question for Mike, actually...

racer504

My Feedback: (2)

Well actually, Norbert is working on some plans. I never had any since I just build from templates. I'm fine with him sharing those with anyone who might be interested. Kind of like an "Open Source Project". Everyone who builds one can throw in their ideas and keep making it better. Mike

Cornelp

Ok, put me on the list!!

I'm already thinking shiny carbon....

norbique

Yes it's true, I am working on a plan for this tunnel boat. With the help of Mike it's slowly taking shape, still it's far from being finished. Lots of parts are still missing (I focused more on the building then the drawing ), and because of the nature of the build, there will have to be a written text, explaining the build process step by step. The plans won't be finished too soon. You probably noticed I slowed down with the building as well, life's intervened. Currently I'm happy if I can spend a few hours a week working on the boat.

norbique

I've done some more work on the boat yesterday night and today.
I began reinforcing the sponson-hull joints and the hull-electronics box joints with epoxy and micro-balloons. I will reinforce the transom as well using the same method.
I finished the electronics box cover and the servo mount.

racer504

My Feedback: (2)

You're getting there. All the hard work is done now. I wish I had the patience to build those neat round cornered hatch covers you do. That is just a really nice touch. I finally got out to run mine this Sunday. I took some video with my phone but got home and found I don't have the cable to transfer it to my computer. Maybe someday... Also in answer to a question on the FE Tunnel thread, mine weighs just a little over 5 pounds RTR.
Norbert is right about the plans. It takes more knowledge of the technique to build like this than plans. (Not hard to figure out, If I can do it anyone can) It starts out with 3 basic templates for the hull and sponsons. About the only special tool required is some sort of foam cutter. It could be done with a saw and some sanding if needed but a foam cutter makes it real clean and easy. It seems like it won't be strong, but it really is.
Mike